Perspectiva

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).