In the 18th century, Voltaire would famously caricature the scholastic emphasis on powers in his claim that for them, opium puts people to sleep because it has a “dormitive power”. Voltaire saw this as an obviously ridiculous tautology that doesn’t explain anything.

The widespread scholastic tendency to see causes as reified “powers”, however, is also implicitly an important counterpole to the bad idea of generalized occasionalism that makes God directly responsible for everything, which is much worse in its consequences than the reification of powers. Any view that sees many reified powers is inherently in conflict with the claim that all power whatsoever is concentrated in a single point, be it God or the emperor. I also think the claim that there is only one real “cause” conflicts with any reasonable interpretation of the meaning of “cause”. Something like this is implicit in Aristotle’s critique of pre-Socratic claims about the One.

The very notion of a human intellective power also seems to rule out the possibility that human understanding could be merely passive in any simple or univocal way. In the previous post we saw that many of the Franciscans asserted a kind of psychological “occasionalism” in the theory of knowledge that — because it is limited in scope, and also treats the individual human intellect as a kind of power — would seem to implicitly conflict with the emphatically unlimited character of the generalized occasionalism that treats all power and causality other than God’s as illusory.

In Duns Scotus the conflict is a bit different. As Boulnois says below, Scotus asserts that there is in part a real causality of the object on the human mind, thus rejecting the psychological occasionalism of his Franciscan peers who denied this. But like them he also aims to follow Augustine in seeing the individual human as having an active intellective power. And at the same time too, he is a radical voluntarist who defends a radical version of omnipotence. An important question will be, how can Scotus (or anyone) be a radical theological voluntarist who also defends radical omnipotence, and not be an occasionalist?

Boulnois continues, “Representation implies a doubling of species. But it also presupposes a continuity of the cognitive activity. For Scotus, as for Olivi, knowledge is the union of two partial concurrent causes, the soul (principal cause) and the body (derived cause). But in his eyes, this is a different model from simple occasionalism: it is necessary to distinguish that which Olivi confused. There is indeed a real causality of the object. [quotes from Scotus:] ‘What is it to excite the intellective power to think: to produce something in it, or not?’ ‘The knowledge engendered in the intelligence is something new, and must have a cause, which is not the soul alone.’ Thus it is necessary to move beyond all the forms of Franciscan occasionalism” (L’Être et représentation, pp. 79-80, my translation throughout).

The emphasis on the production of something recalls the new and original (Avicennan rather than Aristotelian) paradigm of efficient causality as a kind of production, which seems to have been introduced into the Latin-speaking world by Gundissalinus’ 12th-century translation from the Arabic of the great Iranian polymath. This came before the Latin world gained access to the major works of Aristotle. It greatly influenced the development of Latin philosophical vocabulary. Thus Avicenna would help shape the views not only of the anti-Aristotelian Franciscans but also of Aristotle’s defenders Albert the Great and Thomas Aquinas.

The preeminent example of this kind of production would be God’s act of creation, but at the same time this view sees efficient causes in the world as providing examples of production everywhere. Only God is said to truly create from nothing, but the real production of some effect becomes the general model of what it is to be a cause.

A natural cause in this view is also more than the minimalist “reason why” the becoming of things goes this way rather than that, in the determination by reasons in nature that is propounded in Aristotle’s hermeneutic physics. The very notion of “physical” undergoes a major transformation. A natural cause becomes a power that is supposed to be active in its own right.

Properly speaking, a cause in the scholastic sense is a power that both does something and explains something. The new perspective of efficient causality shared by most of the scholastics sees such powers everywhere. Though the new theory is not Aristotelian, at least the role it seems to give to “secondary” causes is something Aristotle would have appreciated.

“In sensation, the material and extended object is indicated by a form or sensible species, the material and extended trace inscribed in a material and extended subject — the organ of the sensing body. The phantasm is only spiritual in the Stoic sense: it designates a concrete corporeal breath, an ‘animal spirit’. That is to say that it remains material, and there is nothing intelligible about it. How does it come about that we call it intentional? Is this intentionality the true psychic intentionality? Not for Duns Scotus” (p. 80).

As we have seen before, the whole vocabulary of intentionality also originally comes from the Latin translation of Avicenna. For Avicenna, intentionality indeed belongs to the soul. (In the late 19th century, Franz Brentano revived this term and discussed its scholastic origins. Then Husserl made it central to his version of phenomenology, while rejecting Brentano’s “psychologism” and attributing intentionality instead to a non-psychological “transcendental subjectivity”. More recently, Brandom has argued for a version of intentionality that belongs entirely to the realm of meaning, and is not only non-psychological, but does not especially pertain to a subject in the modern sense at all.)

For Scotus, Boulnois continues, “The phantasm is only a singular and material image of a material and singular object. Its intentionality is the pure fact of resemblance, as a statue of Hercules represent Hercules. And since the image is relative to the original, in that it represents it, we call it intention. Intentional being for the sensible species is nothing other than the fact of being a natural resemblance, which replaces the object and signifies it. The sensible species is an image, but not an image seen (unlike the statue of Hercules, which is seen and understood as representing Hercules); it is not seen as an object, but rather shows itself as ratio cognoscendi [reason for knowing]: it is not the perceptive image that is seen, but the thing itself. The intentional being of the phantasm does not belong to the activity of the intellect: for the latter it is an exterior object, an extended thing, material and composed of parts. That is why it is not the principal cause of thought but a partial secondary cause that in fact supports it, by reason of the present colligantia [combination] of soul and body. But it is to the intellect itself that the principal cause of thought belongs (ibid)”

“The operation of thought presupposes the double activity of the knower and the known. Duns Scotus cites Augustine as a leitmotiv: ‘Knowledge is engendered by the one and the other’. In effect, neither of the two taken separately can be the perfect active principle of intellection. Three reasons prove that the sensible species is necessary, but not sufficient: 1) The sensible accident is not an object more perfect than intellection, because it would have to be more perfect than the intelligible form to be the perfect active principle. 2) For an object equally present to the intellect, a greater effort and a greater attention (intentio ad intelligendum) allow a more perfect intellection to be achieved, which means that the collaboration of the intellect is required. 3) The proper perfection of the human is thinking. This comes about not accidentally but essentially, since the represented object is accidentally present to the soul, in a contingent manner. It cannot by itself imply an essential perfection. But neither is the intellect the perfect principle of intellection, because the two senses of representation are constitutive of its noetic function. The representing resemblance and the act of intellect are two aspects of the same way of relating to the object. [quote from Scotus:] ‘The act seems to be a resemblance proper to the object.’ To know, it is necessary first to perceive a representative resemblance. The species comes from the object, as from an exterior principle, and it depends on it essentially, which is why it is related to it by a relation that founds its very being. Thus the object is not only a cause by accident or a sin qua non of intellection, it is an essential cause of it. Intellection has a double characteristic, like every natural sign: it is caused by the object. It refers to it essentially” (pp. 80-81).

This two-sided view reflects a reading of Augustine that brings him closer to the way I read Aristotle.

“A theory of partial concurrent causes fully applies here. The object and the intellect concur, each actively but partially, in intellection; taken together, they constitute an integral and total active cause. With this condition, it is manifest that the texts of Augustine militate not for a total constitution by the intellect, but for a causality of the object united with that of the intellect. We can say at the same time that the word is engendered by memory, by science in memory, and by the thing known. The word is first engendered by the acquired science in memory, in a first act that suffices for the second act that is the act of intellection. Nonetheless, in this first act of science in habit, the object shines already. It is manifested in the limpid clarity of intellect. But because of this, it is no longer the real cause of actual intellection. The representation in the intellect takes its place. The object is only the term aimed at by this representation, its actual referent. Science is the formal principle of the engenderment of an actual representation. The object is that which ‘shines’ in the principle. Memory is that which contains the principle” (pp. 81-82).

Augustine’s account of the role of memory in thought is quite interesting and original. In some ways it anticipates Husserl’s notion of passive synthesis. Boulnois continues to expound Scotus.

“The phantasm of the common sense makes a representation independent of its presence. The actual presence of sensation is guaranteed by the inscription of a material trace in an organ. But the form of this trace, its configuration, its structure exist only for knowledge. It is not the body that is the total cause of sensation in the soul, but rather more the soul that is the principal cause of sensation, with the collaboration of the object. The resemblance in the soul is not the sensible species received in the corporeal organ, but an intellectual act of knowledge. Every agent by nature has to render similar to itself what it receives, and the object thought is no exception. It renders the intellect similar to itself. The sensible species leads to an immaterial act of knowledge by the soul. The species follows a continuous trajectory, which goes from the information of sense produced by the object perceived, to the act of perception of the object. This perception in its turn is ‘a certain quality’ of the soul, ‘a certain resemblance of the object, undoubtedly more perfect than the previous resemblance, which we habitually call “species” ‘. After a first representation, the sensible species, the act of knowledge is a second representation, distinct but into intellect — intelligible” (p. 82).

Here again we see a significant explicit reference to presence in what Scotus calls the act of knowledge.

“Scotus’ second line of argument is offensive. The intellectual species is necessary, first of all to explain the presence of the object to thought. — The intellect perceives differences that sensation ignores, because the phantasm does not represent them: only the intellect is turned toward the universal and discerns the quiddity of the object. From the individual conditions furnished by the phantasm — quality, quantity, figure, place, time — the intellect separates the notions apprehended in a complex whole. Scotus integrates in this form the discursive work of thought shown by Aristotle. To abstract is to separately form the species that represent each of these elements in the absolute: object, whiteness, figure, etc. The noetic plane reflects the linguistic analysis of predication: the predicate (albus [white]) recalls a substantive quality (albedo [whiteness]) that we can distinctly name. For [quote from Scotus:] ‘the phantasm does not compete with its species’: all that it represents, it represents as singular, in relation to another, and conjointly. When the intellect abstracts, it forms within itself the species representing these notions: species that are separate from one another and that serve for science, having a universal and autonomous object. It allows the object to be apprehended under its essential reason, detached from its accidental characteristics” (pp. 82-83).

Scotus has a very original and interesting account of the origin of universals in a “formal a priori”. We associate this kind of language with Kant, but as Boulnois will point out much later, this is a Scotist motif in Kant that Kant inherits from the Wolffians. But apparently there is no Scotist analogue for the Kantian synthetic a priori.

“Next, the intelligible species is necessary to explain the formation of the universal. Knowledge does not repose on a theory of abstraction, on a denuding of the sensible conditions that particularize the singular thing, finally to release the essence dissimulated under the corporeal accidents. No more are there forms innate in the intellect. The possible intellect does not contain the universal in advance. It is a pure receptivity. Is it therefore necessary to deny universals? Certainly not. ‘From this evidence, that the intellect can think the universal, I take this proposition: “intellect can have an object that is universal in act, present by itself to itself in its reason as object, and naturally anterior to the act of thinking”. From this follows the hypothesis that in this anteriority (in illo priore), there is an object present in the intelligible species, and thus there is an intelligible species anterior to act.’ Duns Scotus rejects an empirical genesis of the universal. He no more admits innate concepts or ideas, and proposes a new theory, that of the objective a priori. Universality comes neither from sensation nor from divine illumination. It is a condition of possibility preliminary to the act of thought, following from the intelligible structure of our intellect itself, because it always aims at an object. This is present, as in Olivi, as object or term of thought. But unlike in Olivi, this presence is the result of a real (but partial) causality of sensation” (pp. 83-84).

Here among the Franciscans we seem to be witnessing the origin of the modern concept of “object”. Again we see it intertwined with presence. Though it is common to see universality associated with intellect, I did not recall the unique way that Scotus explains universality, in terms of what it is to be an object. Further below, he will also say that the universal is the relation of representation to things. Universality is associated with what Scotus will call “objective” being.

“Universality is an a priori structure, anterior to the act of thinking. [quote from Scotus:] ‘The object is anterior in nature to the act. Universality, which is the proper condition of the object as object, precedes the act of the intellect or the act of intellection. It is necessary that the object also be present under this reason [universality], for the presence of the object precedes the act.’ Universality is nothing other than the status of object as object. Objectity is synonymous with universality, since it is detached from the res [thing] in its singularity, its existence, and its mode of presence. For in order that I be able to think an object in act, it is necessary first of all that it be present as object to my thought. There is indeed an a priori to my act of thinking — the object’s objective presence as species or intelligible form” (p. 84).

Again Boulnois uses Heidegger’s term “objectity”. Though it has partial antecedents among his Franciscan peers, this whole line of thought in Scotus is extremely original, and largely developed in opposition to Aristotle. To turn things around and blame this Scotist novelty on Aristotle as Heidegger does is nothing less than an act of violence, and the height of perversity. And again, Heidegger should have been in a position to know better, since he wrote his dissertation on Scotus.

“The agent intellect makes the sensible species an intellectual form like itself, adapted to the subject in which it is received — the patient intellect” (ibid).

Boulnois switches back and forth between “potential” intellect and “patient” or “passive” intellect, probably reflecting the usage in his source materials.

“The agent intellect [quotes from Scotus:] ‘makes the non-universal a universal’. ‘Since the universal as universal is nothing in existence, but only in something that represents it under this or that reason, these words have no sense, unless it is because the agent intellect produces something that represents the universal, starting from what represented the singular.’ The universal is not an existing thing but the relation of representation to things. Thus the imagination presents a particular phantasm to the patient intellect; the agent intellect imprints a form representing all the objects of the same species. The universal, or what comes down to the same thing, the objective being, is ‘a relative being’ (secundum quid), since it is ‘the being of the represented’ in the representation. The Scotist noetics is a theory of transposition. It rests on a chiasm: the material object produces the assimilation of the intellect to its distinctive traits, but at the same time the intellect assimilates the object in making it pass from material nature to spiritual nature. The continuity of traits is engendered by the object; the distinction between natures is maintained by the intellect. Resemblance is made according to the formal being of the thing, difference according to the mode of being of the subject intellect” (pp. 84-85).

“Formal” being is another name for what Scotus calls “objective” being, associated with universality. This again is a very novel concept that is essentially unrelated to form in Plato and Aristotle.

“How is the ‘transfer’ from the sensible species to the intelligible species accomplished? In virtue of the Scotist analysis, it is necessary that the intelligible species be really distinct from the sensible species, that it be the result of an effective causality. But how do we guarantee that it corresponds well with what it represents? Scotus raises the problem in his Questions on Metaphysics: ‘The cognitive power has the task not only of receiving the species of an object, but also of tending by its act toward that object. And the second point is more essential to the power, because the first is only required because of an imperfection of the power. And the object is more principally object, because the power tends toward it, only because it imprints a species. And it is manifest: if God imprinted a species in the intellect, or in the eye, the latter would comport itself in the same way toward the object as now, and its object would be an object in the same sense. But God is not an object, because the power does not tend toward him, and nonetheless it is He who imprinted it.’ Scotus’ solution consists in making intellect the principal cause of intellection, associated with a partial concurrent but secondary cause, the impression of a species in the possible intellect. And the object is only an object insofar as it is aimed at by the act of knowledge, or term of knowledge. It is more essential for it to be the term aimed at than to be the moving principle. We cannot say that the object of knowledge is reduced to its moving cause, the phantasm: ‘The cognitive power must not only receive the species of the object, it must tend by its act toward the object’. Duns Scotus distinguishes the (nonessential) origin of thought from intentional aim, which is essential. It is not necessary to confound the species received from the exterior in the possible intellect to imprint on it the form of the thing, with the intelligible species produced from the interior by the agent intellect, in order to aim at an object, imprinting its reason in the possible intellect. The two acts are indistinguishable in the present state, but their signification is different. Thus Scotus separates two aspects in the species: what comes causally from the thing itself (the formal content), and what comes from the activity of thought (the aim at an object). The empirical reception of a form means less than the structuration of an intellectual a priori, for constituting the object as object of thought” (pp. 85-86).

Amid all the promotion of efficient causes, it is interesting that intentionality here is characterized as an aim that is essential to thought.

“In so doing, Scotus opens another question, which will become essential for Peter Auriole and Ockham: it is no longer necessary that it be the object itself that causes its representation. It could be produced by another, since God has the power to produce this effect. As a consequence, he can cause the representation of a thing in us independent of its existence” (p. 86).

Most of the later Latin tradition adopts the emphasis on existence and causes of existence from Avicenna. But unlike Aquinas, Scotus does not mainly associate being with existence. For Scotus, the mark of univocal being will be none other than representability.

“In admitting an effective causality of sense, Scotus reconciles the noetics of Augustine with those of Aristotle, the intellectuality of the mind with the collaboration of the phantasm, while reducing the latter to the congruent portion. The phantasm is necessary, but it does not suffice to represent the universal. The eidos received in the imagination is imprinted in the possible intellect, and represents its object under this or that aspect (sub ratione repraesentabilis). The phantasm is sensible and singular; it represents nothing but the sensible and the singular. As [the Latin] Aristotle says, ‘the agent intellect is essentially (mere) an active power’. Nonetheless, its act is not abstraction. The agent intellect cannot act on the phantasm to dematerialize it, or denude it of its accidents, for the good reason that it cannot act on the phantasms at all. The agent intellect cannot act directly on the sensible species, without itself becoming extended and material like it. If the product of the agent intellect were [quote from Scotus:] ‘received in the phantasm, the term received would be extended. The agent intellect would be incapable of effecting the transfer from one order (of reality) to another, and the term received would be no better proportioned to the possible intellect than the phantasm itself’. As a consequence, the agent intellect acts in its proper order, and metamorphoses the sensible image into an intelligible one. It is not limited to denuding the sensible image, but gives its status of object to sensation, in producing a reality in the possible intellect. It does not abstract, it transposes into another order” (pp. 86-87).

I have defended the way Aristotle talks about abstraction as exemplifying a careful minimalism that avoids speculation. But to insist on a quasi-literal “denuding” of the sensible image as Averroes does is not satisfying. The idea of a two-sided causality in which both the intellect and the thing play an irreducible role seems more in line with Aristotle’s general attitude and his hylomorphism.

“Finally, the intelligible species explains the birth of science. It is not simply [quotes from Scotus:] ‘a habit acquired from frequent acts, which facilitates [the repetition] of such acts’ but ‘that by which the object is present as intelligible in act, whether it is the intelligible species or something else’. In effect, the species is an anterior condition of knowledge in act, since it permits the passage of an essential power to act. It precedes all actual intellection, all knowledge acquired through repeated acts. This is a formal a priori condition, and not an a posteriori empirical acquisition. Scotus cites as proof the definition of Aristotle: science only occurs in the intellect by a change in the intellect itself. It has [quote from Scotus:] ‘a form by which the intelligible object is present to the intellect — and this form is anterior to the act of intellection, since the proximate power by which someone is capable of thinking is anterior in nature to the act of intellection’. Between the sensible phantasm and the act of intellection an intermediate moment is interposed — the constitution of an intelligible species. This does not come from a divine illumination, but plays the role of a formal a priori” (p. 87).

“Science” here is a state of knowing in the soul. Again I am impressed by Scotus’ denial of both illumination and innate ideas.

“The intellect [quote from Scotus:] ‘cannot apprehend the object without this species’, and reciprocally, the species cannot represent the object under a reason other than that under which it is apprehended. The traits of resemblance are those of the intelligible species. They render it absolute and precise, that is to say distinct from all others. — Broadly speaking, the first active moment of intellection for the agent intellect consists in engendering an intelligible species from the phantasm in the imagination. In effect, that which is present to the intellect is either the intelligible species itself, or a [quote from Scotus:] ‘certain reason under which shines the intelligible in act’, that is to say a representation that has for its referent the objective being of the thing represented. And this representation, says Duns Scotus, ‘to put it briefly, we call an intelligible species’. The intelligible species has passed entirely under the regime of representation. This engendering of a ‘representation’ is a real generation: the representation is a thing produced by the agent intellect, and is distinct from the intellect that contemplates it as the very thing that it reproduces. But at the same time, the object becomes intelligible, from the imaginary thing that it was. For sure, the engendering of the object is metaphorical: it remains the same thing, to which we relate under a different point of view, insofar as it is intelligible, and not insofar as it is sensible. But its objective being (the angle under which it is represented, its very status as a representation) has now changed. ‘Such is the corresponding representation, such is the objective being that the object possesses in being represented.’ The representation’s status is really changed: from a corporeal image, it becomes a spiritual image; from a singular, it becomes universal; from being received, it becomes produced. If we recall that the representation is a signifier, following this transfer it is the same referent that is now aimed at by a different signification, which is the more strict and more rigorous definition of the metaphor. When the representation changes really, the objective being of the represented is subject to a metaphoric transfer” (pp. 87-88).

On a broader arc, we will begin to see here in detail why Heidegger’s claims about “Western metaphysics” are so wrong.

After his fascinating detour on what could legitimately be called the 13-century science of perspective, Boulnois adds another dimension to the dossier of medieval theories of representation, summarizing intricate Franciscan views about sensible and intelligible “species”. Duns Scotus’s defense of intelligible species will distinguish him from his Franciscan colleagues.

Boulnois not only shows strong explicit connections between representation and “presence” in several important medieval authors. His archaeological investigation of the larger conceptual world around Duns Scotus shows specific historical sources in medieval philosophy for what numerous 20th-century writers have taken to be uncritical modern notions of “objects”, and for the reduction of being to objects, which Heidegger claims typifies “Western metaphysics” as a whole.

I’ve long been fascinated by the 14th-century controversies over species. The rather limited modern scholarship that exists on this point most often frames it in terms of a debate between nominalism and realism about universals, understood as competing theories of what kinds of things there are. That is one aspect, but these disputes also deeply involved the theory of knowledge; what might in a very broad sense be called issues in phenomenology; and a kind of psychology, concerned with details of the functioning of the soul in matters of perception and thought.

Indeed in this section Boulnois does not even mention nominalism. But before leaving it aside though, for another angle on the larger picture it is worth recalling that nominalism radicalizes one side of Aristotle’s assertion (often read as a criticism of Plato) that concrete real things have a kind of primacy, and generalities have a kind of secondary status. Modern scholarship has given most of its attention to the nominalism of William of Ockham, who indeed did belong to the Franciscan line that will be discussed here. But Duns Scotus and non-Franciscans like Walter Burley mounted a strong defense of the realist alternative, to which modern scholarship has been less attentive. Realism here is meant not in the ordinary practical sense, but in the sense of an assertion that universals and other beings of reason have a kind of “reality” of their own, even if we do not literally believe in Platonic forms.

Until the last few decades, the study of Latin philosophy was dominated by Thomists who tended to see Aquinas as towering over others, and focused on him as the leading representative of a “moderate realism” that avoids the respective excesses it sees in both nominalism and Platonism. But Thomas came too early to participate directly in the 14th-century debate, and the major defenders of the realist side, like Scotus and Burley, did not visibly appeal to Aquinas.

The American pragmatist Charles Pierce provocatively referred to himself as a “Scotist realist”, but did not write substantially about Scotus, which left his references somewhat mysterious. I am still skeptical about this.

Boulnois sets the stage by summarizing relevant views of Aristotle, Augustine, and Avicenna.

“Nonetheless, the vision of an image resides ‘not in the eye, but in one who sees’ [Aristotle, On Sense Perception]. ” (L’Être et représentation, p. 67, my translation throughout).

This is a nice example of Aristotle’s thoughtful minimalism. “One who sees” refers simply to a whole human individual or other living being in ordinary experience. (Living beings are hylomorphic wholes, whose division into soul and body is a derivative abstraction. “Soul” for Aristotle is neither a speculative entity nor an object of faith, but a way of speaking about the life and character of living beings.)

Boulnois continues, “Not only is the theory of representation deployed in the order of signs and that of images, it concerns knowledge. It rejects all the problems of perception in the perceiving subject, and opens up a scission between the object and the form that resembles it in the knowing subject” (ibid).

“Theory of representation” here refers particularly to the 13th and 14th century views he will be discussing.

What is meant by “knowledge” in this passage is not what I call knowledge in the strong sense — a major feature of which is that it can and will explain itself and respond substantively to questionings — but rather a more general and personal kind of “experience” of knowing that is not involved with dialogical challenge.

As to the rejection of problems of perception in this 13th and 14th century tradition, the qualifier “in the perceiving subject” is essential. Insofar as the account of sensible species is mainly causal, the place of questions of interpretation in our experience of sensibles is greatly reduced. But even if we ultimately reject it, this causal account of perception should be recognized as a substantial theoretical development in its own right.

The scission or cut that he speaks of is not unlike the rift between mind and world in the later and better known representationalism of Descartes.

“How is this scission elaborated? How are we to understand the mode of being of each of these two terms [object and form], and how shall we interpret their correspondence?” (ibid).

In future posts, the notion of object introduced here will undergo some very interesting elaborations. Boulnois briefly recalls the elementary account of sense perception in Aristotle.

“In sensation, a mutation intervenes; a new image surges in the soul. Aristotle distinguishes a form and a matter in sensation: ‘For each sensation, it is necessary to know that sensation is the receptor of sensible forms (aistheton eidon) [which Boulnois here, following the Latin, translates as sensible “species”], just as wax receives the imprint of gold or brass, but not as gold or brass’ . By perception, the soul receives the impression of a form or sensible species (eidos), without the matter that it informs, in the place in which it is inscribed originally’ [quoted from On the Soul, book II] (p. 68).”

In this account of sensation and perception, we have a perfectly non-spooky example of a form’s relative independence from matter. I think Aristotle meant “impression” as a kind of metaphor. But taking it more literally allowed the Latin theologians to overlay Aristotle’s metaphor with Stoic-influenced medieval causal accounts of sense perception.

Boulnois turns to the Augustinian context, so important for the Franciscans. Augustine takes orientation from concerns far removed from those of the Stoics, for whom nothing exists apart from body. In the 13th and 14th centuries, these extremely different views were fused together in a series of remarkable syntheses.

“Augustine adopts this remark, but seeks to make it agree with another: since the spirit is immaterial, nothing of the sensible can act on it. It is the soul that perceives, that produces a sensation in itself when it perceives the sensible body. Sensation is neither a brute sensorial shock nor the simple reception of an image, but rather its production by the soul encountering a material object presented by sense. [quote from Augustine:] ‘While the image begins in the mind, this same image is not produced by the body in the mind, but by the mind itself with a stupefying rapidity.’ This suddenness shows that it is not the bodies seen that produce the images in the mind, but indeed the mind in itself, in its intellectual nature. There is no action of the body on the mind, but an autoaffection of the mind by itself. [quote from Augustine:] ‘The soul undergoes something by the very operations [of sensation], and nonetheless it undergoes nothing from the body, but is acted on by itself.’ Just as the soul cannot bring bodies themselves into its spiritual nature, in sensation [quote from Augustine:] ‘it rolls into itself their images, and delights within itself in these images made by itself. It gives them something of its own substance to form them’. The mental image resolves the drama of Narcissus: in the incapacity of possessing the object, the soul produces an image, in which it finds its satisfaction. Unable to play in a complete image of itself, it monetizes this impossible plenitude, coining multiple images where it is with itself. Thus in sensation the soul forms in itself the images of the things known, in order to possess a spiritual equivalent of the same nature as itself. It recovers from the constitutive alienation of the object. This image has for its subject of substantial inherence the soul, and not the bodily organ of sensation” (pp. 68-69).

This influential Augustinian view, which treats perception as an activity of the soul, is the direct opposite of the passivity of sense perception that the Latin tradition attributed to Aristotle. The “other view” preceding Augustine that Boulnois alludes to is presumably that of Plotinus, who was Augustine’s most important philosophical influence.

I think that for Aristotle, the commonly cited passivity of sensation is only a first approximation that — like other seemingly definitive introductory statements in Aristotle, such as the account of substance (ousia) in the Categories — is intended to be superseded upon more thorough investigation, like that for ousia which Aristotle carries out in the Metaphysics. On closer inspection, at the very least the work of synthesis in the “common” sense — which enables us to experience things and the world in coherent and meaningful ways — is active.

“The specific vocabulary of repraesentatio is developed in parallel to this, in the Latin translation of the Treatise on the Soul of Avicenna. Avicenna holds that there is a conservation of sensible species on the plane of imagination: while raindrops succeed one another, singularly and distinctly, sensed separately the one from the others by the external senses, we perceive a continuous line constituted by their series. Thus the common sense or imagination constitutes this straight line in a first perceptive synthesis. It centralizes the forms received by the five senses, thus transposing sensation into perception. But this synthesis is temporalizing: at the moment when the drop falls, the common sense perceives the drop [quote from Avicenna:] ‘as if it found itself there where it was, and also there where it is, and thus it sees a rectilinear extension (distensio recta)’. While the external sense perceives the thing there where it is at a given instant, the common sense constructs a continuity, that is to say an extension that is of the same nature as the temporal extension of the soul (distensio animi according to Augustine). It does not perceive the thing there where it is, but it perceives it in the mode of ‘as if’: as if it were in two distinct places, and in the relation of the two instants, past and present, as between these two places, here and below, in a synthesis that apprehends them as distinct and unifies them in the movement of their dissociation. Because we must call upon a schematism, the objects of sensation pass, but the phantasm retains them in a continuous presence, [quote from Avicenna:] ‘even if the thing that has already passed has been destroyed’. In the fleeting and discontinuous frame of the sensed world, it separates a form, which is not the fixation of the external object, but an ‘as if’, a substitute, a redoubling in continual permanence — a first representation” (pp. 69-70).

In passing, we see here that Avicenna developed a more explicit account of the synthetic functions Aristotle attributes to the “common” sense. This has intrinsic interest in its own right, but I will not pursue it here.

In the Latin Avicenna, “The word [representation] appears in order to describe the apprehension of an external object by the imagination, precisely to distinguish it from the act of thought. Representation governs the status of the image, and indeed of the imagination. This is why it guarantees the separation between intellect and sensible imagination: intellect knows itself, directly and without an organ, as distinct from the imagination, which does not represent itself, but [quote from Avicenna:] ‘only represents an image taken from the senses’. In a remarkable manner, [Avicenna’s Latin translator] Gundissalinus translated numerous Arabic terms that describe the act of imagining by ‘repraesentare‘, as if he wanted to unify the vocabulary of imagination under a single concept. The term designates the action by which the estimative faculty, a sort of first sensible judgment, recalls with a great ‘speed’ (as in Augustine) the forms that are in the imagination, and re-presents them [quote from Avicenna:] ‘in such a way that it is as if it saw the things to which the forms belong’ ” (p. 70).

But for the Latin Avicenna, representation (repraesentatio) belongs to the imagination, rather than to thought, as it will for Scotus.

Avicenna’s neoplatonic rather than Aristotelian view that “intellect knows itself, directly and without an organ”, not only in God but also in the human, was welcomed by Latin Augustinians.

“The encounter of the two Platonisms, those of Augustine and Avicenna, is effectuated at the same time as the translation of the latter by Gundissalinus. But it is above all affirmed in the 13th century, in what Gilson called ‘Avicennizing Augustinianism’. As William of Auvergne underlined, following Augustine: the intellect does not receive material forms, and nonetheless perception depends on the sensible. How is the difficulty resolved? The response is found in occasionalism. ‘New thoughts or dispositions supervene in the intellectual substances’, by sensible ‘occasions or excitations’. Science begins with sensible experience but is not derived from it, since its nature is intellectual. The sensible is a condition sin qua non, but it is not the only principle of knowledge. It is indeed the soul that thinks, but when it applies itself to sensible objects, it passes through the intermediary of images. [quote from William of Auvergne:] ‘Properly speaking, signs do not transmit a light of science, nor the things themselves, but they excite our souls to apply themselves to things.’ There is indeed a transposition of sensible images into intelligible ones, a transposition that is the very status of representation” (pp. 70-71).

This limited “occasionalism” in the account of perception needs to be sharply distinguished from the generalized occasionalism that makes absolutely everything depend in a direct and total way on divine will. It is the total and unqualified character of the latter that effectively abolishes all worldly intelligibility and causality.

“Thomas Aquinas strives on the contrary to explain perception in line with the account in Aristotle: ‘the soul thinks nothing without a phantasm’. Our intellect thinks the forms in sensible images, because it must turn itself toward sensible experience to receive the objects of thought, and to take from it the forms that are thought. Being the instrument of a bodily knowledge, the phantasm also permits the abstraction of intelligible species. The nature of a stone can only be known completely when it is known as existing in the particular. For we apprehend the particular by sense and imagination. [quote from Aquinas:] ‘To know what is in individual matter, but not insofar as it is in such a matter, is to extract a form from the individual matter that the phantasms represent.’ Representation here is simply the relation of substitution and the resemblance assured by the sensible image. The intellect, turned toward this sensible image representing the thing known, abstracts its nature. Thus the intelligible species is necessary; form abstracted from the thing, it allows us to see the intelligible structure of the sensible, and not only its exterior image.”

“Avicennism or Augustinianism? In any case, the Franciscan line rejects intelligible species: the body cannot by itself directly produce anything in the mind, not even a simple and spiritual intelligible species, which suits the simplicity of its subject, since its causality is that of a corporeal and composite being. On the other hand, it is necessary rather to think that the body acts on the soul by way of a natural liaison (colligantia), by an inclination and a formal union toward the soul to which it is related. This concord between the body and the soul, this harmony introduced by the Creator, is such that the action of the one rebounds on the other, so that the diverse powers of the soul concur in one sole and same act. The impression produced in the body arouses a movement in the soul that corresponds to that in the body, but it is only the occasion, since their metaphysical distinction prevents there being causality of the body on the soul. To think the relation between soul and body, the Franciscan school proposed diverse solutions: the object is an occasional cause or exciter [John Peckham and Roger Marston]; or a simple cause sin qua non [Olivi]; or it is limited to inclining the soul to know [Mathew of Aquasparta, Henry of Ghent]. In all these cases, there is no direct causality of the soul or of the body by itself in the production of knowledge. For Olivi, this is explained by a concurrence of two causes of different orders. It is thus that many people row a single boat, adding their forces together, producing one sole and same movement of the boat. [quote from Olivi:] ‘Each collaborates in pulling the boat, yet none is the total cause.’ Knowledge is the occasional union of concordant partial causes, which produce a single effect. The model is also that of carnal union: as in the union of man and woman, the species is engendered in memory following an immaculate [sic] conception; the species [quote from Olivi:] ‘is engendered in the maternal womb of the intellect itself’. The species, engendered in the womb of the intellect, is the fruit of a copulation between memory and intellect” (pp. 71-73).

All the great Franciscan theologians are strong voluntarists, a position I regard as truly horrible in its consequences. But their arguments about perception and intellection are quite subtle and interesting.

“Perception is susceptible to a double interpretation: physical for the transmission of information, phenomenological for sensation; sometimes as the reception of an act coming from a movement, sometimes as total and apperceptive knowledge of an intentionality. — Bacon knows only a multiplication of material species: ‘species are a material and natural being in the medium and in the sense’. These also transmit spiritual qualities (in the material sense of Stoic spiritus), and perceptions [apercues] by the intellect”. [quote from Bacon:] ‘This spirituality is contrary neither to corporeity nor to the materiality we find in material and bodily things’. If the sensible species is the resemblance to the substance that caused it, it transmits the intelligible intentio. [quote from Bacon:] ‘This is why the sensitive soul can perceive the substance by its species.’ Knowledge presupposes that the sense and the intellect are modified by a sensible effect or a material impression. But in the intentional multiplication, it is the form that acts. In this sense, the species is not only material, but spiritual or intentional: it can act on the sense organs and the powers of perception. [quote from Aquinas:] ‘The form is received in the patient without matter, insofar as the patient is rendered similar to the agent according to the form, and not according to the matter. And in this way, the sense receives the form without matter, since the form has being in a different way in the sense and in the sensible thing. For in the sensible thing, it has a physical (naturale) being, and in the sense an intentional and spiritual being’. The sensible, for example color, at first has a natural being in its objects. But it has an intentional being for the soul. The sensible cause produces an intentio; it intentionally engenders a similar [form] in the medium, then in the organ of sight, by an act of illumination. Thus at first the sense considers the external sensibles, then the rational soul perceives the intentiones that are in the imaginative power and that glow in the phantasm [citations to Henry of Ghent]: glowing, shining, appearing; this expression is almost a pleonasm; we cannot separate the brilliance from what is shown in it, the appearance of the form from its appearing, the phainomenon from the phantasma” (pp. 73-74).

As with representation, the vocabulary of “intentions” comes from the Latin translation of Avicenna. “Apperceptive” is a later term, only introduced by Boulnois by way of description.

“How do we articulate a knowledge already constituted by the laws of optics with the functioning of thought? Beyond the reception of the sensible species, subject to the general laws of perspective, how does representation emerge for the thought that receives it? — Henry of Ghent focuses on three problems: 1) ‘color is other than the species of color’; what we know, beyond the sensible species, is color: how do we sustain the claim that the material species transported by the luminous ray is at once a visual image (the species of the color) and the object rendered visible (with its color)? Why redouble the object with its species? 2) ‘The species of color is abstracted by a quasi-real separation, and by a generation or multiplication of the species in the totality of the medium in which they are found, between the thing and the point of the eye where the visual power is exercised.’ But where is the abstraction situated: is it already prefigured by the separation of the material species emitted outside the subject, or must it be accompanied by an intellectual act, which separates the intelligible species from its material substrate? 3) The operation of the intellect in any case produces only the intellection of the universal. How do we guarantee that this universal corresponds to the singular perceived by the sense? And how can the sensible singular act on the intellect, when the sensible cannot act on the intelligible?” (p. 74).

Boulnois’s phrase “knowledge already constituted by the laws of optics” is quite striking. On this account, a kind of “knowledge” in experience comes before thought, and has its own constitution that is independent of thought. This is one way in which the theory of perspectiva will be applied.

Henry of Ghent was the senior theological consultant in the proceedings that led to the reactionary condemnation of 1277 (though he is said to have had reservations about parts of the final version). Here he appears in a more interesting light.

“For Henry, the same representation is at play in sensation and in thought. [longer quote from Henry:] ‘Such is the process of the act of vision: in the first instance, material light falling on a particular material color radiates outside it. Second, abstraction produces a species of the color without matter. Third, the medium by this species provokes an act of vision…. Fourth, the light of the intellect radiates on the particular phantasm, thanks to which the imagination (phantasia) exists in act. And in this way, it abstracts a universal phantasm from the particular. It poses it before the possible intellect, as the proper object that affects it…. [It allows it to know] the universal thing of which it is the species, so that it is not abstracted from this universal thing, but is a particular phantasm abstracted from a particular exterior thing, since in this way it exists as universal.’ Henry starts from the phantasm as sensible, and means to resolve the noetic problems starting only from the particular representation in the phantasm. It is the light of the agent intellect that separates the universality already present in the phantasm.”

“Thus precisely because the sensible species is already a representation, knowledge has no use for intelligible species. Criticizing the analysis of Thomas Aquinas, Henry from the start rejects intelligible species in the beatific vision, then in all knowledge, which generalizes the argument and turns it against Thomas: [quote from Henry:] ‘The presence of the object is the cause of the presence of the species, and not the inverse: in effect, it is not because the species is in the eye that a white object is present, but the inverse; indeed the first representation of the object is not by a species; as a consequence, it is superfluous to posit a species by reason of the presence of the object.’ If we knew only by representations, our knowledge would fall into idealism. The thing itself is presented to sense and intellect; it has no need of a species to mediately take its place” (pp. 75-76).

A strong thematization of presence is here asserted and developed by Henry of Ghent in a direct and explicit way that is quite unlike the implicit dependence on presence that Heidegger tendentiously claims to find already in Aristotle. We will see more indications like this.

“No more does knowledge have need of intelligible species for Olivi. Nonetheless, knowledge is not effectuated by the naked essence of the cognitive power, but through a mediation. If only for rendering an account of memory, it is necessary to posit the retention in sensible memory of remembered species of sensible objects, [quote from Olivi:] ‘as for universal objects, as when someone thinks the general or specific quiddities of sensible things and absent things taken universally. In effect, these sensible things taken universally cannot be represented by an imaginative species’. In all acts of knowledge, sensible and intelligible, [quote from Olivi: ‘a view (aspectus) is required, having for its actual term an object (super obiectum actualiter terminus)…. This is why, when the exterior thing is not itself presented directly for this view (non obicitur aspectui), it is necessary that there be [… in its place] a species in memory, which is only the principle of the cognitive act as a terminative and representative object.’ In the absence of a real object, knowledge turns its regard toward a substituted object, which is not the causal principle of its vision but the term of its view, and which by its triple status of substitute, effect, and resemblance recalls the absent thing. The sensible species takes its place, it represents it, but only as the term of its view and not as a cause” (p. 76).

These are quite sophisticated accounts.

“If the occasion allows the division between sensation and thought to be preserved, representation allows their continuity to be guaranteed, and the transposition of one into the other. Knowledge is not produced by its object. It is rather the object as term that is produced by the soul under the form of a substitute. [quote from Olivi:] ‘For knowledge or thought of absent objects, it is necessary that a species take the place of the object.’ Even if the thing is not present, the object of its view remains, and the species takes the thing’s place: [quote from Olivi:] ‘It is necessary that an image of the thing be made the object of our regard and be its term.’ The substitutive presence of a representation allows the absence of the cause to be made up for. If the object is lacking, a function of presence gives thought its term: [quote from Olivi:] ‘The thought of an absent thing cannot occur without the cooperation of a presented (praesentialis) object’. The power cannot by itself render its objects present, unless it could render them all present, without limit, and make itself equal to God. It receives its determination of a presence, direct or substitutive. [quote from Olivi:] ‘It is necessary that either the object be presented to it, or that it it be represented in an imagination in such a way that the act of knowledge is applied to the object itself or to its image configured or assimilated to it. And this configuration is the specific reason of the act itself.’ The need for presence manifests the constitutive finitude of the human: it is filled by a representation” (pp. 76-77).

In Olivi too, we see a very explicit thematization of presence.

“On [the matter of the existence of intelligible species], Scotus detaches himself from his Franciscan predecessors. While maintaining continuity with the Baconian theory of the sensible species, he renews the intelligible species, which he like Thomas Aquinas judges to be necessary. The presence of the object to thought does not render vain that of the species. [quote from Scotus:] ‘The object relative to a power has in first place a real presence, that is to say such a proximity that it can engender this species in the intellect, which is the formal reason of intellection. In second place, by the species thus engendered, which is an image of its generator, the object is present under its status as knowable, or as represented’ ” (p. 77).

Here we see Scotus too explicitly thematizing presence.

“In a first moment, the form of the intellection by which the object is presented in intuition is already a species. But its matter is the real presence of the object. In a second moment, the species is imprinted in memory: it is the image itself in its status as image that is perceived; the representation is known as such. The species is indeed the cause of the presence of the object, contrary to what Henry of Ghent affirmed: it is the cause of its presence as thinkable, abstract, independent of the existence of the object — the cause of its real status. This thesis is fundamental: it clears the way for a new acceptation of truth as ‘objectity’, since it leads to clearing the way for a double presence of the object — the real presence of the thing, and the objectual presence of the represented. The thing receives a being as object insofar as it corresponds to a representation” (pp. 77-78).

Boulnois’s use of the term “objectity” implicitly recalls some translations of Heidegger’s Objekität. Heidegger not implausibly considers this “objecthood” to be the product of an objectifying attitude, in which an object is presented for a subject as something external (a view that finds its ultimate expression in modern technology).

But Heidegger writes as if he himself were the first to recognize the alienating aspect of a subject-object duality, which is ridiculous. He then proceeds to blame this alienation on a monolithically bad “Western metaphysics” that he claims to trace back all the way to Plato and Aristotle.

There is no greater obstacle to responsible and insightful “historiography” than this kind of sweeping, ahistorical, monolithic negative interpretation.

And ironically, this kind of gesture — which purports to invalidate all previous philosophy with one blow — owes its fashionable status to none other than Descartes, from whose subject-object dualism Heidegger claims to be the only one who can save us.

In an upcoming post, we will see in much greater detail how a concept of objecthood or “being an object” comes to plays a novel, central, and very explicit role in the work of Duns Scotus, on whom Heidegger wrote his dissertation. In light of his early concentration on Scotus, Heidegger should have been in a position to be aware of this. But as far as I know, Heidegger never even mentions the historical role of Scotus and his near-contemporaries in his frequent later allusive, broad-brush denunciations of Western metaphysics.

Boulnois on the other hand sees a great originality in Scotus on this point.

“Scotus’s argument is polemical: the position of Henry is not tenable. According to him, the same sensible representation, presented in the light of the phantasm, represents a singular thing, and in a second light, that of the agent intellect, it represents another, the universal; thus glowworms appear in the light of day as colored objects, and at night as luminous sources. But according to Scotus, the representation, the sensible species, is at first a thing that is presented in its proper light. Without this the same species, if we placed it in different media, would change its nature: in the vibration of the air, it would represent a sound; in the illuminated air, a color. Quite the contrary, there is a ‘unity of the representation and of the object representable by it’: the representation is not simply a thing that would entertain diverse relations to diverse objects, but its relation to this or that object is constitutive of its being as a representation. The same species, that is to say ‘the same representation’, always represents the same representable, and according to the same reason. Put under a greater light, an identical representation represents no other thing, but the same thing more clearly: the same species of black or white better reveals what it represents in the sun than by moonlight; and reciprocally, the glowworm gives rise to two distinct representing species, that of a colored body and that of a luminous source, which represent diverse objective beings, diverse aspects of the same being. We cannot follow Henry, for whom whereas the phantasm reveals a representation of the singular, the light of the agent intellect reveals a representation of the universal. The sensible species represents the singular, and in the light of the agent intellect it represents it more clearly, so the intellect can think it better. But it in no way represents the universal. It never represents the universal qua universal, whatever light illuminates it. It is necessary to produce another representation and another relation of representation to be able to perceive the universal. The remarkable trait of this refutation is its systematic interpretation of the theory of species, sensible or intelligible, in terms of representation. The denuding of the sensible species never allows knowledge of the universal if it is not already given to us as a representation. If with Henry of Ghent we enter into a theory of representation at the level of the phantasm, it is necessary to go all the way and admit a second, intelligible form of representation. Thus we cease to see the phantasm as the appearance of the very nature of the thing. The agent intellect produces an intentional form. It is not limited to bringing to light the content of the phantasm, as Henry believed. And Scotus insists: if we hold absolutely to preserving the vocabulary of illumination, it is necessary to specify that this light is productive, that it is an efficient cause and not the denuding of a formal aspect of the phantasm” (pp. 78-79).

Like Aquinas, Scotus apparently chooses to overlook Aristotle’s clear explanation of what it is to be a “source of motion or change”, and substitutes for it the very non-Aristotelian notion of what came to be commonly called “efficient causality”. This explicitly makes creation the primary model for worldly causality. Where Aristotle emphasizes the diversity of causes of one thing, this dubious application of the creationist model encourages the reifying view that each thing or state of affairs in ordinary experience has one “efficient” cause that is responsible for its being in the sense of existence.

We will see in a moment that the Latin term causa efficiens is already applied to what is called a “cause of existence” in the 12th-century Latin translation of Avicenna. But this has a different meaning in Avicenna, for whom creation is a necessary eternal emanation from the Necessary Being. The mainstream of theologians writing in Latin assumed that God’s act of creation must be understood as free in a very strong sense, and not as governed by any necessity.

For Aristotle, the primary and essential source of motion or change that causes the bronze statue to come to be as what it is, is the art of bronze-casting (Physics book II ch. 3; Metaphysics book V ch. 2). For Aristotle, granted that there is a real production involved, nonetheless the maker of the cast, the one who pours molten bronze into it, and their actions and tools are all merely “accidental” or incidental contributing causes of the real production of the statue, which is due primarily to the art of bronze-casting. Real production is causing something to come to be what it is, or causing it to have the form that it does.

If we were to apply Aristotle’s own concept to the creationist context that Aristotle never considered, the “source of motion” would then be something like God’s wisdom, and more particularly the content of that wisdom. Leibniz would later take this path. But the Latin tradition generally regards the content of divine wisdom as inscrutable to humans.

Avicenna in the Metaphysics section of his great work The Healing (translated to English as The Metaphysics of The Healing) openly claims to have improved on Aristotle’s Metaphysics. For example, Avicenna says that the discussion of these topics should start with God, pointing out that Aristotle does not do this. He proceeds to begin his own work with a very original account of God as the Necessary Being. While usually putting their own notions of God in place of Avicenna’s, his Latin readers welcomed the general idea of starting with God, and of amending Aristotle to refer to the Creator.

In place of what Aristotle prefers to calls the “sources” (archai) of motion and change, Avicenna substitutes what in the Latin translation was called the causa efficiens or “efficient cause” as the cause of a thing’s existence.

Where Aristotle emphasizes that sources of motion and change are usually complex and plural, in this later tradition there seems to be an assumption that the cause of a thing’s existence ought to be simple.

Where Aristotle emphasizes that “cause” is said in many ways, Avicenna, Aquinas, and Scotus effectively assert the preeminence of Avicenna’s cause of existence over all the Aristotelian ones.

The Latins generally follow Avicenna in substituting a non-Aristotelian cause (what would be aitia in Aristotle’s Greek) of existence for what Aristotle prefers to call the arche (“source” in Sachs’s translations) of motion and change. For Aristotle, nature (physis) is the source (arche) of motion and change in natural things. Real production is the coming-to-be of a form.

For Avicenna and the Latin tradition — historically far more influential on this point than the text of Aristotle — real production is causing something to have being in the sense of existence. This is what in Latin was called efficient cause. The preeminent example of real production for the Latin tradition is God as Creator making something from nothing.

Avicenna was translated to Latin earlier than the major works of Aristotle, and the Latin terminology forged by his translator Gundissalinus was then used by later translators of Aristotle.

Ibn al-Haytham (ca. 965 – ca. 1040), known to the Latin practitioners of perspectiva as Alhazen or Alhacen, has been called the father of modern optics. The well-documented Wikipedia article says that his seven-volume Book of Optics, which builds on Ptolemy, Euclid, Galen, and Aristotle, was frequently cited by Kepler, Galileo, Huygens, and Newton. I won’t dwell here on his scientific contributions, which were many; what I find especially interesting is his clear articulation of what Helmholtz in the 19th century would call “unconscious inference” in sense perception.

A notable advocate of critical thought, Ibn al-Haytham wrote that “I constantly sought knowledge and truth, and it became my belief that for gaining access to the effulgence and closeness to God, there is no better way than that of searching for truth and knowledge” (quoted, Wikipedia).

“Truth is sought for its own sake … Finding the truth is difficult, and the road to it is rough. For the truths are plunged in obscurity…. God, however, has not preserved the scientist from error and has not safeguarded science from shortcomings and faults. If this had been the case, scientists would not have disagreed upon any point of science” (ibid).

“[T]he seeker after the truth is not one who studies the writings of the ancients and, following his natural disposition, puts his trust in them, but rather the one who suspects his faith in them and questions what he gathers from them, the one who submits to argument and demonstration, and not to the sayings of a human being whose nature is fraught with all kinds of imperfection and deficiency. The duty of the man who investigates the writings of scientists, if learning the truth is his goal, is to make himself an enemy of all that he reads, and … attack it from every side. He should also suspect himself as he performs his critical examination of it, so that he may avoid falling into either prejudice or leniency” (ibid).

“From the statements made by the noble Shaykh, it is clear that he believes in Ptolemy’s words in everything he says, without relying on a demonstration or calling on a proof, but by pure imitation (taqlid); that is how experts in the prophetic tradition have faith in Prophets, may the blessing of God be upon them. But it is not the way that mathematicians have faith in specialists in the demonstrative sciences” (ibid).

José Filipe Silva in “Perceptual Judgement in Late Medieval Perspectivist Psychology” (2017) writes that “Alhacen has an instrumental approach to faculty psychology, in the sense that he is interested in providing an account of visual perception in terms of functions and mechanisms, rather than in terms of faculties. In that sense, he causes a problem to his medieval interpreters who operate … under the framework of Avicennian faculty psychology” (pp. 1-2).

“A primary concern of late medieval philosophy is how things are made available to perceivers in such a way that they are perceived in an accurate manner. Because things cannot be themselves immediately present to the senses, one needs to posit some form of representation that makes things available. Two issues follow from this: the first concerns the nature of these representations, in terms of their power to represent (what they represent), and the second their ontological status in the medium and in the senses, i.e., the kind of existence or being they have” (p. 2).

“[S]ome late medieval authors seem to have become aware of the limitations of an account of cognition that allow us, as finite beings, to build accurate representations of the external world and its objects on the basis of (the processing of) incoming sensory information by our sensory faculties…. Perspectivist optics tries to address these concerns by strengthening the process of producing and certifying the final product, the image of the external thing acquired by visual perception, by rational-like processes — namely by judgment and inference” (p. 3).

” ‘[D]ifferentiation between two greens is not the actual sensation of green’. But this is still perception by sight; or, better, it is a case of seeing (‘it occurs in sight’) while not being ‘the sensation of colour’…. [T]his visual property can only be perceived by comparison (per comparationem) and discrimination (per distinctionem). According to Alhacen, such an operation is accomplished by what he calls the power of discrimination, the virtus distinctiva. The important and original claim is that any instance of visual experience consists of both the perception of the form that is seen and the further act of discrimination, which is the perceptual judgment, e.g., of comparison. A basic distinction is then at play between: (i) perception at first sight (comprehensio solo sensu) [and] (ii) perception by judgment (comprehensio per distinctionem/cognitionem/scientiam)” (pp. 4-5).

I think such a view is also implicit in Aristotle. What distinguishes Ibn al-Haytham in this regard is that he makes it very explicit.

“There is another function of the faculty of discrimination that resonates to a contemporary mind: it can recognize the perceived object without having to go through all its characteristics, provided it has previously encountered that thing…. Alhacen therefore introduces yet another level: (iii) perception by means of reasoning (comprehensio per argumentationem/sillogismum). According to this last type, perception in the robust sense, i.e., as the perception of all properties/intentiones constituting the sensible form, must include what has often been called (unconscious) sensory inference, because the perception of some of those properties is dependent on acquired knowledge and presupposes a process akin to reasoning: the immediate grasping of a conclusion that follows from the premises without knowing the relation of entailment between premises and conclusion. Alhacen notes that, even though structurally it operates in a quasi-rational way, such perception does not qualify as cognition in the full rational sense, because it is not linguistic (it does not make use of words)” (pp. 5-6, citations omitted).

“Once it possesses these forms in its imagination and encounters similar instances of the same kind, or the same individual, the soul performs what Alhacen calls the second type of perceptual intuition, which is perceptual intuition with previous knowledge. In these cases, Alhacen describes how cognition or perception takes place when the form which is being perceived is compared with the form which is stored in the imagination, namely to its similarity to a general or an individual form already acquired. If it ‘fits’/corresponds to the universal form, the cognitive power of discrimination identifies the kind to which the individual now perceived belongs, whereas if it bears correspondence with an individual form, it recognizes the individual thing…. But the process is often swifter, because the power of discrimination is able to recognize an individual or a kind on the basis of distinctive or salient features” (p. 6).

“In other words, before one knows what a thing (‘red’) is, one perceives the difference between that thing and other things, i.e., the difference between ‘red’ and ‘blue’; once the knowledge of ‘red’ has been acquired, one begins to immediately see ‘red’ (quod est color, insofar as it is colour, an instance of perception at first sight) followed by the recognition of ‘red’ as the kind of colour it is (cuiusmodi sit color or the quiddity of the colour red)” (ibid).

“All this is done in an amazingly short time, especially in the case of perception at first sight. In the case of perception by judgement and reasoning, which are slower than perception at first sight, the process is faster if the objects are familiar (‘frequently perceived’) to the perceiver. In this case, the perceiver has a form retained in his/her memory to which it has access, and that can be applied to the identification of the thing present to the senses, rather than having to go through the process of discriminating all the intentions that constitute the object’s sensible form. As Alhacen makes clear, this is possible due to the way these properties are made available and the ‘familiarity’ of the power of discrimination with them. But this comes at a cost, as it means that it can make mistakes, as recognition is a step removed from the actual seeing of the visual form, and is dependent on a complex combinatory process” (p. 7).

“[I]f a thing is well-known by the perceiver, some salient properties are enough for its identification and recognition. If, however, that is not the case, and the thing is unknown, the perceptual system – sensory power plus last sensor plus power of discrimination – must act on the entire spectrum of sensory information in order to unveil all of its intentions or sensible properties. Alhacen calls this perceptual intuition (per intuitionem) or ‘visual scrutiny’. Perceptual intuition is therefore the perception of the form of the visible thing with all its properties that includes discrimination and inference. In order to do so, i.e., to get a better hold of the object, the sensitive power will move the organ of sense to see the object from other viewpoints. This scanning process is automatically initiated as the result of the way the visual system is built (natus est visus)” (ibid).

“Finally, this allows also for a conclusion concerning the active nature of the perceptual process: if it were passive, it would simply be perception at first sight, just receiving the impressions of light and colour. As we can conclude from Alhacen’s arguments, it is not. Perception of the object’s visual form (the assemblage of its properties or intentions) is the result of complex and complementary levels of psychological functions, including discrimination, recognition, and inference” (p. 9).

Boulnois sees the Arabo-Latin theory of perspectiva or perspective as inducing a new concept of representation, beyond that found in the Augustinian tradition, that becomes very important in scholastic thought. Over several upcoming posts, we will see a rich interplay between historical notions of resemblance and representation. This makes it hard to sustain the simple picture of these as two globally opposed paradigms.

“The theory of representation does not end in an analysis of signs. The image too takes the place of something. Following Roger Bacon, every image is first of all a sign. But every sign is not an image. The step from signification to resemblance must be taken with rigor. Species are the natural signs of objects, which owe nothing to arbitrariness or convention, but signify their object in virtue of a causal necessity, by their very nature and without imposition. That the image is a natural sign, Bacon had established against Aristotle. Nonetheless, the image does not refer to the original in virtue of a simple inference, but ‘by reason of conformity, of the configuration of one thing to another in its parts and its properties, like images, paintings, resemblances, etc., the species of colors, of flavors, of sounds and all things… In the same way, all the things produced by artisanal work are signs of art itself, and of the impressions and resemblances of these things existing in the soul of the artisan’ [quoted from Bacon’s De signis]. Thus while inference is perceived by a complex mental operation, resemblance offers itself to us in a simple perception, as referring to the original that it imitates” (L’Être et représentation, p. 55, ellipses in original, my translation throughout).

The idea that an image is “more” than signification is striking. But at the same time, it is supposed to be something we can simply perceive. The account of perception here makes perception univocally passive in relation to species. (By contrast, whatever passivity of perception there is in Aristotle is not a strong univocal theoretical perspective. His basic account of the five senses treats them as passive. But sensation is not the whole of perception, as his tantalizing remarks about the active role of the “common” sense in organizing perception and experience make clear.)

Aristotle did not have a theory of natural signs, an explicit general theory of resemblance, or a developed theory of perspective. These are scholastic innovations that have both positive and negative characteristics. From another point of view it might be considered good, for example, not to have a theory of natural signs. But particularly the theory of perspective is a significant accomplishment. For now, I’ll follow Boulnois in letting these views speak for themselves.

The mention of inference as “perceived” is striking. Inference here is not so much an act of intellect as an entailment or implication that is, broadly speaking, “perceived” in things.

Conformities between things “in their parts and properties” could begin to sound like the isomorphism that Brandom singles out as distinguishing a new notion of representation in Descartes. The systematic correspondences between geometry and algebra that Descartes famously highlights are rigorous and exact in a way that analogy in general is not, however.

“The description of images goes much further than general semiotics. Beyond the relations of inference, the mind can come to the knowledge of a resemblance, which establishes par excellence the nature of the sign, as Augustine saw: ‘All desire a certain resemblance in signification, such that signs as far as possible resemble the things signified.’ If the sign is constituted in an image, this is by a surplus of sense: the natural sign is more than a conventional sign, but the image in its turn is more than a trace, more than a simple natural sign. In its plenitude, the image does more than refer to a simple signified. It has its proper thickness; multiple and heterogeneous, it resembles what produces it. Beyond the deciphering of semiotic implications, the sense of the image is deployed up to the play of identity in difference. By this, the iconic privilege of resemblance envelops a whole noetic; it requires a new articulation of image and sign, of resemblance and causality, of object and sense.”

This is an impressively positive view of images. Here we are far from Plato’s critique of imitation. We will see the term “imitation” used in a positive way as well.

The association of resemblance with multiplicity, thickness, and heterogeneity in a “play of identity and difference” here is noteworthy. We are accustomed to stereotypes of medieval views as one-sidedly hierarchical in their reference of everything to God.

The connection of resemblance with efficient causality in the halfway modern, non-Aristotelian scholastic sense is another new development.

“Under the name of the theory of representation, it remains to think at once the unity and the division between a semiotics of inferences and a noetics of images. What is an image? In what does the image differ from resemblance?” (p. 56).

“To clarify the status of the image, the Middle Age relies on the Augustinian theory of the forms of correspondence (convenentia). Augustine in effect distinguishes three connected aspects: image, equality, and resemblance. [quote from Augustine, De diversis questionibus:] ‘For where there is an image, there is a resemblance, but not necessarily an equality; where there is an equality, there is a resemblance, but not necessarily an image; where there is a resemblance, there is neither necessarily an image nor an equality’ ” (ibid).

Boulnois further develops this triangular contrast, treating Augustine as representative of earlier medieval Latin thought.

“The image presupposes a productive principle, and reveals a causal dependency. It implies a resemblance, but not an equality, since it can be deficient in relation to the original, and not express all its traits. Thus in the mirror is found an image of the person it “expresses” (expressa est). Nonetheless it does not exclude equality: an image can be adequate. Equality also implies a resemblance, but not an image. Thus two similar (pares) eggs are equal and resemble one another: all the traits of the one are in the other. But they are not images of one another, for neither is taken from the other or is the expression of the other.”

“Finally, resemblance implies neither an image nor an equality. It is a generic particular trait, without expression or adequation; a pure fact, that of having common traits, but in a transversal manner, without depending on a principle. Insofar as it is an egg, every egg resembles all other eggs; but the egg of the partridge, while insofar as it is an egg resembling the egg of the chicken, is neither its image nor its equal” (p. 57).

This “transversal manner, without depending on a principle” again addresses the multiplicity and heterogeneity in resemblance that he commented on earlier.

“This system opposes the image, causal dependency, and resemblance as a transversal fact, but authorizes a combination of the three concepts. It allows relations to be defined between the Father and the Son (image, resemblance, and equality); between God and the human (image, resemblance, without equality); between two individuals of the same species (resemblance, equality, without image); between the original and its reflection in a mirror (resemblance, image, without equality). Trinitarian theology, anthropology, metaphysics of species, noetics of reflection are tied together around this theory of resemblance, which is oriented toward an end: the theology of the image of God in the divine Trinity, the only case where all three properties, image, resemblance, and equality, are present” (ibid).

For Augustine, metaphors of the Trinity abound, and shed light on other knowledge. He famously used an analogy of the interrelation of three faculties he attributed to the mind — memory, understanding, and will — to make it more intelligible to humans.

“For the Son, image of the Father, constitutes a perfect equality of God with himself. And if there is an image implying perfect equality, it is that which characterizes the relation of parent and child; they are identical generically and specifically, and the parent is the principle of the child. [quote from Augustine:] ‘From the parent is taken (expressa) the resemblance of the son, even if we properly call it image, and it can be taken to the point where it is properly called an equality, except that the parent precedes him in time…. But in God the condition of time does not apply…. It follows not only that the Son is the image of God, because he comes from him; not only that he is the resemblance, because he is the image, but again that he is equal to him’ ” (pp. 57-58, ellipses in original).

“More resembling than resemblance, more essential again than the conception, equality is the accomplishment par excellence of the image. Thus the image culminates in the reproduction of the identical. The theology of resemblance is accomplished in a metaphysics of adequation. It is indeed possible to order the world according to degrees of resemblance, to the point where it contracts into the primordial equality of God with himself” (p. 58).

But all this is by way of contrast to the developments of the 13th century. Here Boulnois returns to his major theme of the status and uses of representation. And in a moment, we’ll get to the fascinating subject of perspectiva.

“From Bonaventure to Henry of Ghent, the authors of the 13th century transpose this system of resemblances into more or less accomplished forms of representation. For Thomas, all effects in some measure represent their cause, but in diverse manners. Certain effects ‘represent only the causality of the cause, and not its form, in the manner that smoke represents fire’. These are signs of inference, which represent as a ‘trace’ (vestigium), for the trace shows the passage of something, but not the nature of that which has passed. Others ‘represent the cause according to the resemblance of its form, as the engendered fire represents the engendering fire, and the statue of Mercury represents Mercury’ — and this representation is called ‘image’, because it participates in the same form. The trace, sign of inference, constitutes the first degree of representation. But the image constitutes the second degree, since it implies a community of form. To cover the entire surface of the thinkable is to follow a system of traces and images, starting from the investigation of adequate representation” (p. 58).

“Over a vast surface of signs and inferences, the order of the image is detached by a turning that is proper to it. It is imposed within the vaster framework of an episteme dominated, at the end of the 13th century, by the paradigm of perspectiva. This discipline includes at once a geometrical optics, a theory of vision, and a psychology of perception. It is inscribed progressively in the disciplines of the quadrivium [the part of the liberal arts that includes arithmetic, geometry, music, and astronomy], taught in the faculty of arts. Medieval perspective rests on a certain number of simple principles, deployed by the main Arabic, and later Latin, theoreticians of this discipline: Al-Kindi, Al-Hazen, Avicenna, Robert Grosseteste, Roger Bacon, and John Peckham.”

“1) Light by its nature follows a rectilinear trajectory from its source to its destination, passing closer and closer through the intermediary points in the medium that propagates it. It is possible to interpret the propagation, reflection, and refraction of light according to laws of equal proportionality, the laws of geometry.”

“2) The same law extends from punctual sources to extended objects. In effect, each point of an illuminated or colored object radiates independently following straight lines. Light can integrally transmit an image of the object in each of its points, and thus constitute a coherent figure. This form, species, or resemblance is transmitted by transparent media in act to polished surfaces, from which they are projected. The experience of a dark room proves this: when light passes through a small opening, the image takes the form of the luminous source, and not that of the opening. The luminous rays are transported according to the geometrical laws of figure, color, and all the visual qualities of the object. ‘It is necessary to give all the causes of natural effects by lines, angles, and figures…. A natural agent propagates its power by itself to the receiver, whether it acts on the senses or on matter. This power is sometimes called a species, sometimes resemblance, and this is the same thing’ [quoted from Al-Hazen (Ibn al Haytham), De aspectibus]. Resemblance is emitted by the thing and transmitted by light, according to the laws of geometry.”

“3) In this visible image, the closer the points are to the center of the luminous cone, the more they are affected by the radiation of many points, and the more they receive an intense radiation. This is the phenomenon of the penumbra.”

“4) The eye itself is one optical system among others. Vision is effectuated by images (species) propagated from the visible object to the eye. It is produced by a pyramid of rays that has for its base the object, and for its summit, the eye. The rays penetrate the organ of vision, the lens of the eye; by geometric projection, they give birth to a proportional image of the original, which is precisely the visual impression. The lens effectuates the perception of every object thanks to the perception of each of its points, but the more powerful and efficacious rays are those that are perpendicular to the surface. Thus visual sensation is nothing but the reception of the species induced by the visible according to its proper laws.”

“5) The eye is an organ destined to receive images, and not to form them or to emit a ray that is then reflected by the object. Vision is the reception of the form of colored bodies on the surface of the lens. It is an information, or a faithful passive impression, produced by a real form emitted by the object.”

“6) The form deposited on the lens is transmitted to the brain by the vitreous humor and the optic nerves. The nerves are hollow tubes full of animal spirits, which form a medium capable of conducting by a series of forces the very image of the object (including its color and configuration) to the brain, the stronghold of internal sense. But the final perception takes place after the meeting of the two optic nerves, which superimpose the images from the two eyes in a cavity of the brain. This is the only place where species are no longer propagated in a rectilinear manner. Besides the proper and common sensibles (size, figure, and movement), the species equally transport complex qualities, which are transmitted by sense, but discerned by the intellect” (pp. 58-61).

Bacon’s major work in this area is entitled The Multiplication of Species.

“We underline here that the species are propagated in being multiplied. It is not the same accident that migrates from one subject to another, but its conforming copy. The object engenders the species of light and color in the point adjacent to the transparent medium that surrounds it, which does the same, and so on. The continuous multiplication of species follows the rays issued by all the points of the surface of the object, until it encounters an opaque obstacle: a quality numerically distinct, but specifically identical, is transmitted to the subject immediately adjacent, until it reaches the ultimate receiving subject. The species or resemblances thus transmit the accidents of the object to the eye, where they are impressed. The transmission of the image passes by the actualization of the medium in potentiality (the diaphanous), to the sense organs and the cavities of the brain that house the internal senses. Thus it is the same visible form of the object that is transmitted by the exterior transparent medium and the apparatus of vision (vitreous humor, optic nerve, which constitute a transparent internal medium). The concrete image of the object is neither reversed nor encoded: — it is not reversed, because the rays are refracted by the posterior surface of the lens without intersecting, as distinct from the inverted images in dark rooms; — it not encoded, because it is the same visible image, transported by the diaphanous medium”, that is emitted by the object, received by the lens, transmitted by the optic nerve, and seen in the brain. Medieval perspective is binocular. It applies to moving eyes that can inspect objects part by part, and converge on a mobile observer, capable of evaluating the relative position of objects in relation to her own body.”

“The same geometry governs the propagation of light and the projection of images in all the optical systems: the shadow cast, the dark room, are all subject to the same laws. Perspective is a paradigm that presides over the destinies of the propagation of light, of vision, and of knowledge. It at once furnishes the law of the visible and the content of visual images. It is given for a passive registration of the real, by a natural and necessary reflection. Resemblance is objective; it founds, in the order of nature, the projections of shadows and light, of measures and images. It organizes the regime of representation in the register of the visible.”

“But the paradigm extends beyond optics: the propagation of species follows the same rules for auditory and olfactory species. Thus the objects of perception multiply the sensibles proper to each sense. The propagation of the real species in a physical medium explains the causal effect of the exterior object on the sense organ: the sensible qualities do not act directly on the organs of sense, but at a distance and by the species; then the species are centralized by the common sense, combined and separated by the imagination, to recompose an image of the exterior object. Beyond the visual image, the law of representation governs every sensation, instructs every form of knowledge before governing every species of thought. The species is the immaterial subject of causal activity, which traverses all the media, and which applies its effect as a resemblance of an original efficient cause. Roger Bacon gives expression to the universal principle of causality: ‘Every efficient cause acts by its proper power, which it exercises on the adjacent matter, as the light (lux) of the sun exercises its power on the air…. This power is called resemblance, image, species, and it is designated by many other names…. This “species” produces all action in the world, because it acts on the sense, on the intellect, and on all the matter of the world, to engender things.’ Every cause radiates resemblances. Things operate at a distance in engendering the species that are similar to them, so that nature is a system of similitudes: each point in the world emits a species that expresses it, and the world is constituted by the resonance of all these expressions.”

“Thus the resemblances are not produced by perception, but transported by light, even if no one perceives them. An autonomous structure, similitude organizes nature, founds the general expression of substances, institutes the relation of the world to itself, without necessarily passing through the medium of an act of knowing. Action at a distance, magnetism, the influence of the stars on the earth, the reflection of an image in the mirror, the imitation of God by the human intellect, all these operations are rays of resemblance. By it, the world curves its spirals on itself. Similitude is the new name for the order of the world. The world, garden of resemblances, represents itself to itself” (pp. 61-63).

Now we come to an important distinction.

“Contrary to perspective in the Renaissance, medieval perspectiva does not designate the place of a subjectivity. It does not impose any privileged point of view. Space is an atmosphere in which objects are situated in relation to each other without any common measure, and without the predominance of the eye of the spectator. The order of the visible world is not a symbolic form that determines the proportions between objects, but an attribute of bodies, an immanent structure. Medieval perspective does not have for its object quantifiable extension, but figures and bodies. Olivi thus says that the distance of the object from the eye, which is the index of the position of the object, is not a thing, and does not produce any representation of itself. It is not visible by itself: ‘The quantity of intermediary space cannot be represented by the species of the thing that exists at the end of that space.’ The only representable quantity is that of visible form, and not that of space. Space is only the envelope of bodies and the archipelago of figures, a differentiated, discontinuous system of finite extensions. Space is not a homogeneous form, a continuous quantity, but the emergence of figures, the source of the appearance of similitudes: anisotropic, heterogeneous, it is oriented and centered by the subjects that are emitters of species, in a general heterotopy. In the invisible frame of transparent media, resemblance renders visible, as it were jerkily, the diaspora of the world.”

“The tree of identities and differences comes first of all to find a home in the space opened by perspective. It is this order of resemblance that metaphysics will tighten, replace by its proper convenentia, by an order of congruence, a hierarchized order of identities and differences, where the diverse is unified by a measure of extension that is more vast, generic, transcendental, or conceptual. These resemblances, which go by numerous names — images, resemblances, idols, phantasms, simulacra, forms, intentions, passions — are distributed over three levels:”

“– Perception is a global knowledge of figure, at once a perception of the form of the whole, of the relation of this form to its parts, and of the relations among the parts. [quote from Al-Hazen:] ‘The power to distinguish distinguishes all the forms that come from it. It distinguishes the colors of the parts, the diversity of the colors, and the ordering of the parts among themselves.’ “

“– Knowledge of a species is engendered by its cause. It is indissolubly the effect and the resemblance of the agent on the patient, but without destroying it, without total conversion of its matter. [quote from Roger Bacon:] ‘The patient rests in its specific nature, but it is rendered similar (assimulatum) to the agent by the species.’ The species presupposes a substrate able to receive and be modified by it. All knowledge is a knowledge by species, since in the act of knowing, the soul is rendered similar to what it knows, while remaining substantially identical. Knowing is only an effect of resemblance, an effect induced on the organs of sense, on the internal sense and on the imagination. The matter of the sensory organ and the nature of the sensitive soul are the subjects of the affection constitutive of knowledge. The species representing a thing and the thing of which it is the species have the same specific nature, even if their mode of being differs. The representation by species is again an effect of resemblance. It guarantees the order of the world, and maintains the classification of species.”

“– Intentio. [quote from Avicenna:] ‘Intentio is what the soul apprehends in the sensible, even if the external sense does not apprehend it at first.’ The external sense apprehends the exterior form, but the intentio is perceived by the internal sense. It is thus, says Avicenna, that the lamb apprehends, behind the exterior form of the wolf, its intentio, that is to say the reason why it should be afraid and flee, which the sense cannot do. Intentiones have an ambiguous status: they are at once the res [thing] sent by the object, and the result of an intellectual operation of abstraction. The intentio refers to a thing aimed at (intendere), but it is not itself that thing: imagination can apprehend a thing by an intention when the thing has disappeared. This vocabulary, taken from the Latin translation of Avicenna, refers to the concept, to the form of the essence as secondary substance (mana), but here, in the sense where intentio is definitional form, less perfect and less real than the thing it defines. The species [quote from Roger Bacon:] ‘is called intentio in the common usage of the physicians; they say, in the reason of the weakness of its being in relation to the thing, that it is not truly a thing, but more an intentio of the thing, that is to say a resemblance.’ Sensation, at once global and distinctive, makes particular properties appear, which define the objective aspects of the thing seen. [quote from Al-Hazen:] ‘It distinguishes generally all the intentiones of the thing seen, which appear by vision and by the total form of the thing seen, composed of these intentiones.’ Thus the total form integrates, aggregates for perception many real aspects, which we can separate, analyze in it — the intentiones, which make it the object of an abstraction.”

“The image sensed becomes the image thought. Perception deposits an image, and renders objects present to the mind. This process guarantees a real, causal, connection between mundane reality and concepts. Principle at work in nature and in science, in perception and in the concept, perspective extends to phantasms and concepts, beneath the division between imagination and logical thought. It serves as the model for a whole coherent tradition, which claims a new form of truth, the philosophy and theology of representation. Perspective institutes a physical, perceptive, and noetic correspondence between objects in space and their representation. Perceptive and psychological mechanism, it allows access to the world by an ensemble of images, the representations already produced by the world itself.”

“In the order of natural causality, the sensible species represents the object that caused it. That is why it allows the inverse trajectory: starting from the image, we can infer its object in a probable way, thus building a science. In the order of artificial causality, it signifies (and implies) the art of the artisan, but it resembles naturally, not its cause but the object it represents. If causality goes from the thing to the species, there is a natural relation (at least probable and constant) of resemblance, which goes from the species to the thing. Words and species refer to things: words are not the species of things, because they are imposed arbitrarily, but they engender a species in relation with the thing which the word was imposed to signify. The vocal sound is not caused by the species of the thing (or else there could not be many languages), and it does not signify it directly, but it is coordinated with it, since the one like the other refers in a convergent manner to the thing. Knowledge and signification are two different relations to the thing, but they presuppose one another. The species is a natural sign that is adjoined to the conventional signification of language. The order of resemblance and the order of signification are two distinct pieces, but articulated the one to the other in a system of general semiotics.”

“Perspectiva is not only a description of natural causality in the domain of the visible, but the general grammar of resemblance, which institutes the order of things in the register of representation. The order of representation is an objective regularity, universal, determining from outside all the process of perception, of knowledge, and of thought. Law of objective configuration, it builds an ordered, coherent, and finite world. And if the observer belongs to the order of representation, it is as a subject in the in the sense of a receptacle, one support of representations among others: the eye is a subject of representation in the same way as water, air, or the wall in a dark room, for example. If it sees, it is because it is installed in the visible, considering it from a certain place, at the summit of a cone of rays, and bombarded with a bundle of images. It is not a luminous consciousness facing the dazzling tapestry of the visible, for it belongs to the world as one of its parts. Representation brings on the scene the human in the theater of the world” (pp. 63-67).