Aristotle on Explanation

Book 1 chapter 1 of Parts of Animals provides an overview of Aristotle’s perspective on explanation in general. It is a nice synthetic text that brings together many of Aristotle’s core concerns, and shows his vision of how natural science ought to fit in with broader philosophy.

He begins by distinguishing between mere acquaintance with an area of study and being educated in it. “For an educated [person] should be able to form a fair judgment as to the goodness or badness of an exposition” (Complete Works, Barnes ed., vol. 1, p. 994). This seems to apply to any subject whatsoever.

Next he raises the more specific question of method. “It is plain then that, in the science which inquires into nature, there must be certain canons, by reference to which a hearer shall be able to criticize the method of a professed exposition, quite independently of the question whether the statements made be true or false” (ibid).

Continuing to emphasize the critical thinking that is the mark of an educated person, he makes it explicit that some of the most important questions about a subject are what I would call second-order questions, having to do with how we ought to approach the matter at hand. The educated person will give due emphasis to these, rather than naively rushing to deliver judgments on questions of fact.

“Ought we, for example (to give an illustration of what I mean) to begin by discussing each separate substance — man, lion, ox, and the like — taking each kind in hand independently of the rest, or ought we rather to lay down the attributes which they have in common in virtue of some common element of their nature? For genera that are quite distinct present many identical phenomena, sleep, for instance, respiration, growth, decay, death, and other similar affections and conditions…. Now it is plain that if we deal with each species independently of the rest, we shall frequently be obliged to repeat ourselves over and over again; for horse and dog and man present every one of the phenomena just enumerated” (ibid).

The educated person looks for explanations, not just facts or correspondences. The specific “dogginess” of a dog, for example, does not explain its sleeping, breathing, and so on. Instead these activities, which it shares with many other animals, are explained by natures common to all of them.

Further, the kind of method Aristotle commends to us is not a matter of following recipes by rote. Instead, it is a thinking approach that involves persistently following the thread of explanations wherever it leads.

“So also there is a like uncertainty as to another point now to be mentioned. Ought the student of nature follow the plan adopted by the mathematicians in their astronomical demonstrations, and after considering the phenomena presented by animals, and their several parts, proceed subsequently to treat of the causes and the reason why; or ought he to follow some other method? Furthermore, the causes concerned in natural generation are, as we see, more than one. There is the cause for the sake of which, and the cause whence the beginning of motion comes. Now we must decide which of these two causes comes first, which second. Plainly, however, that cause is the first which we call that for the sake of which. For this is the account of the thing, and the account forms the starting-point, alike in the works of art and in works of nature. For the doctor and the builder define health or house, either by the intellect or by perception, and then proceed to give the accounts and the causes of each of the things they do and of why they should do it thus” (p. 995).

He raises the question of which kind of cause comes first, because he wants to suggest a different answer from that of the pre-Socratic “physicists” who attempted to explain everything by properties of different kinds of matter. Elsewhere he says that Plato and the atomist Democritus (whose writings are lost) did better than others at following the thread of explanation, but he considers the elaborated account of ends or “that for the sake of which” to be one of his own most important contributions.

Notably he only mentions two kinds of cause here, rather than the classic four. Similarly, there are passages in other texts where he lists a different number of categories than the canonical ten from the Categories. Later authors often viewed things like causes and categories in a reified, univocal way, as susceptible to exact enumeration. But for Aristotle, these are abstractions from a concrete reality that comes first, to be wielded in a context-sensitive way, so the canonical enumerations are not absolute.

Aristotle’s understanding of the “beginning of motion” is different from that promoted by early modern physics. Conventionally in the reading of Aristotle, the “beginning of motion” is associated with the efficient cause, and these two terms are understood in a somewhat circular way, which is really informed by some broadly intuitive sense of what a “beginning” of motion is. Early modern writers assumed that this “beginning” must be some kind of immediate impulse or force. Aquinas associated it with God’s act of creation and with the free acts of created beings. For Aristotle himself it is neither of these.

My best reading of efficient cause is that it is the means by which an end is realized. In many cases the end is realized not by just one means but by a hierarchy of means (e.g., art of building, carpenter, carpenter’s hammer, hammer’s blow). Aristotle and the scholastics emphasized the top of such hierarchies (e.g., the art of building for Aristotle; God or some metaphysical principle for the scholastics), whereas the early moderns emphasized the bottom (e.g., the hammer’s blow), akin to the proximate cause of concern to liability lawyers. For Aristotle, the art of building and not the hammer’s blow is the true “beginning” of the motion of house construction, because it provides the guiding thread of explanation for the whole process of building the house. But even the art of building is still just a means that gets its meaning from the reasons why we would want to build a house in the first place.

He continues, “Now in the works of nature the good and that for the sake of which is still more dominant than in works of art, nor is necessity a factor with the same significance in them all; though almost all writers try to refer their accounts to this, failing to distinguish the several ways in which necessity is spoken of. For there is absolute necessity, manifested in eternal phenomena; and there is hypothetical necessity, manifested in everything that is generated as in everything that is produced by art, be it a house or what it may. For if a house or other such final object is to be realized, it is necessary that first this and then that shall be produced and set in motion, and so on in continuous succession, until the end is reached, for the sake of which each prior thing is produced and exists. So also is it with the productions of nature. The mode of necessity, however, and the mode of demonstration are different in natural science from what they are in the theoretical sciences [e.g., mathematics]…. For in the latter the starting-point is that which is; in the former that which is to be. For since health, or a man, is of such and such a character, it is necessary for this or that to exist or be produced; it is not the case that, since this or that exists or has been produced, that of necessity exists or will exist. Nor is it possible to trace back the necessity of demonstrations of this sort to a starting-point, of which you can say that, since this exists, that exists [as one might do in mathematics]” (ibid).

In Aristotle’s usage, “nature” applies to terrestrial things that are observably subject to generation and corruption. He earlier referred to astronomical phenomena like the apparent motions of the stars and planets as “eternal” because on a human scale of time, these are not observably subject to generation and corruption. For Aristotle, absolute necessity could only apply to things that are absolutely unchanging. We may have a different perspective on astronomy, but that does not affect the logical distinction Aristotle is making. His key point here is that things subject to generation are not subject to absolute necessity. Leibniz took this a step further and argued that hypothetical necessity is the only kind there is. Kant, in arguing that hypothetical and disjunctive judgment (“if A then B” and “not both A and B“) are more fundamental than categorical judgment (“A is B“), made a related move.

Hypothetical necessity has a particular form that is worth noting. As Aristotle points out in the quote above, under hypothetical necessity “it is not the case that, since this or that exists or has been produced, that of necessity exists or will exist”. To give a positive example, hypothetical necessity says that to continue living, we must eat. But it does not in any way dictate a particular series of motions that is the only way this can be accomplished, let alone the whole series of eating-related actions throughout one’s life. Neither does it dictate that we will eat in any particular instance.

How we meet a particular need is up to us. The reality of this flexibility built into nature is all we need to explain freedom of action. Humans can also affirmatively embrace commitments and act on them; that too is up to us. Freedom is not an arbitrary or supernatural power; it simply consists in the fact that nature is flexible, and many things are up to us.

Aristotle contrasts the way a thing is naturally generated with the way it is. “The best course appears to be that we follow the method already mentioned — begin with the phenomena presented by each group of animals, and, when this is done, proceed afterwards to state the causes of those phenomena — in the case of generation too. For in house building too, these things come about because the form of the house is such and such, rather than its being the case that the house is such and such because it comes about thus…. Art indeed consists in the account of the product without its matter. So too with chance products; for they are produced in the same way as products of art” (pp. 995-996).

“The fittest mode, then, of treatment is to say, a man has such and such parts, because the essence of man is such and such, and because they are necessarily conditions of his existence, or, if we cannot quite say this then the next thing to it, namely, that it is either quite impossible for a man to exist without them, or, at any rate, that it is good that they should be there. And this follows: because man is such and such the process of his development is necessarily such as it is; and therefore this part is formed first, that next; and after a like fashion should we explain the generation of all other works of nature” (p. 996).

This way of reasoning backwards from an essence to its prerequisites is complemented by the fact that for Aristotle (and Plato) essences themselves are a prime subject of investigation, and not something assumed. “Begin with the phenomena”, he says.

Many 20th century philosophers have objected to presumptuous talk about the “essence of man”, and to any explanation in terms of essence. But these objections presuppose that the essence is something assumed, rather than being an object of investigation as it clearly was for Plato and Aristotle. Here also it is needful to distinguish between what we might call the distinguishing essence of humanity used to pick out humans — e.g., “rational/talking animal” — and what Leibniz later called the complete essence of each individual. Clearly also, the parts of the human body do not follow directly from “rational/talking animal”, but from many other attributes “presented in the phenomena”. It turns out that humans share these attributes with other animals, and they can therefore be conceptualized as attributes of common genera to which we and those other animals belong.

Because essences themselves are a prime subject of investigation and are ultimately inferred from phenomena, the kind of teleological reasoning Aristotle recommends always has a contingent character, which is how it naturally accounts for what the moderns call freedom. This contingency is built into in the “hypothetical” character of hypothetical necessity.

“Does, then, configuration and color constitute the essence of the various animals and their several parts? For if so, what Democritus says will be correct…. And yet a dead body has exactly the same configuration as a living one; but for all that it is not a man. So also no hand of bronze or wood or constituted in any but the appropriate way can possibly be a hand in more than name. For like a physician in a painting, or like a flute in a sculpture, it will be unable to perform its function” (p. 997).

Aristotle was the historic pioneer of “functional” explanation. Here he insists that the essences of living beings and their parts must be understood in terms of their characteristic activities. This development for the sake of biology parallels the deeper development of the meaning of “substance” in the Metaphysics as “what it was to be” a thing, and as actuality and potentiality.

“If now the form of the living being is the soul, or part of the soul, or something that without the soul cannot exist; as would seem to be the case, seeing at any rate that when the soul departs, what is left is no longer an animal, and that none of the parts remain what they were before, excepting in mere configuration, like the animals that in the fable are turned into stone; if, I say, this is so, then it will come within the province of the natural scientist to inform himself concerning the soul, and to treat of it, either in its entirety, or, at any rate, of that part of it which constitutes the essential character of an animal; and it will be his duty to say what a soul or this part of a soul is” (ibid).

Here it is important that we consider soul in the “phenomena first” way that Aristotle develops it.

“What has been said suggests the question, whether it is the whole soul or only some part of it, the consideration of which comes within the province of natural science. Now if it be of the whole soul that this should treat, then there is no place for any philosophy beside it…. But perhaps it is not the whole soul, nor all of its parts collectively, that constitutes the source of motion; but there may be one part, identical with that in plants, which is the source of growth, another, namely the sensory part, which is the source of change of quality, while still another, and this is not the intellectual part, is the source of locomotion. For other animals than man have the power of locomotion, but in none but him is there intellect. Thus it is plain that it is not of the whole soul that we have to treat. For it is not the whole soul that constitutes the animal nature, but only some part or parts of it” (p. 998).

Aristotle’s opposition to treating the soul as a single lump reflects his overall functional, activity-oriented, and phenomena-first approach.

“Again, whenever there is plainly some final end, to which a motion tends should nothing stand in its way, we always say that the one is for the sake of the other; and from this it is evident that there must be something of the kind, corresponding to what we call nature” (ibid).

Overall teleology always has to do with tendencies, not absolute determinations. He begins to wrap up this introduction by giving another example of the hypothetical necessity whose concept he pioneered.

“For if a piece of wood is to be split with an axe, the axe must of necessity be hard; and, if hard, must of necessity be made of bronze or iron. Now in exactly the same way the body, since it is an instrument — for both the body as a whole and its several parts individually are for the sake of something — if it is to do its work, must of necessity be of such and such a character, and made of such and such materials.”

“It is plain then that there are two modes of causation, and that both of these must, so far as possible, be taken into account, or at any rate an attempt must be made to include them both; and that those who fail in this tell us in reality nothing about nature” (p. 999).

Again, the two modes here are “that for the sake of which” and the phenomena associated with generation. Considering either of these in isolation yields an incomplete understanding, as we see respectively in bad scholasticism and bad empiricism.

“The reason why our predecessors failed to hit on this method of treatment was, that they were not in possession of the notion of essence, nor of any definition of substance. The first who came near it was Democritus, and he was far from adopting it as a necessary method in natural science, but was merely brought to it by constraint of facts. In the time of Socrates a nearer approach was made to the method. But at this period men gave up inquiring into nature, and philosophers diverted their attention to political science and to the virtues that benefit mankind” (ibid).

Socrates and Plato initially pioneered the notion of “that for the sake of which”, but in turning away from the phenomena of generation and becoming, they gave it a somewhat one-sided character.

The subtle way in which Aristotle wields the concept of essence avoids treating it as an absolute, or as something strictly univocal. In any given context, there is a clear relative distinction between essence and accident, but the distinction is not the same across all contexts. Hypothetical necessity provides the mechanism by which what is “accident” at one level of analysis can be incorporated into “essence” at another level. (See also Hermeneutic Biology?; Aristotelian Causes; Secondary Causes; Aristotle’s Critique of Dichotomy; Classification.)

Aristotle’s Critique of Dichotomy

Chapter 3 of the extraordinarily rich book 1 of Aristotle’s Parts of Animals contains a strong critique of the notion of classification by dichotomy, with implications reaching far beyond its original context. The idea that he criticizes is Platonic division into As and not-As, which is intended to result in a binary tree structure (i.e., a tree-shape in which all the branches are binary).

Platonic division was perhaps inspired by the two-sided character of Platonic dialectic, which was concerned with impartially examining the implications of both sides of some disputable question, particularly in the form of arguments for and against some thesis or other. Aristotle’s own dialectic has a more general form that is not bound to arguments for and against, but rather is simply concerned with an impartial examination of the consequences of hypotheses.

But in any case, classification in a world is a different problem from that of impartially examining a single hypothesis.

Ignoring Aristotle’s lesson, and strongly influenced by the more general impoverished notion of logical judgment as grammatical predication, early modern writers on natural history attempted to follow an a priori theory of univocal classification. But for Aristotle, there is no a priori theory of classification. Instead, the starting point is what Kant would call the implicitly schematized manifold of a concrete world.

Aristotle points out that if classification were reducible to the assignment of predicates, then to consistently classify a world or any given collection, there would have to be some one order in which we divide things by one predicate, then another, and so on. By examples he illustrates the fact that by this method, it is impossible to arrive at the division of animal species that we recognize in nature.

He also makes the more general argument that half of the classifying terms in any classification by sequential predication will be negatives, and that negative terms cannot be properly subdivided.

“Again, privative [negative] terms inevitably form one branch of dichotomous division, as we see in the proposed dichotomies. But privative terms in their character of privatives admit of no subdivision. For there can be no specific forms of a negation, of Featherless for instance or of Footless, as there are of Feathered and of Footed. Yet a generic differentia must be subdivisible; for otherwise what is there that makes it generic rather than specific? There are to be found generic, that is to say specifically subdivisible, differentiae; Feathered for instance and Footed. For feathers are divisible into Barbed and Unbarbed, and feet into Manycleft, and Twocleft, like those of animals with bifid hoofs, and Uncleft or Undivided, like those of animals with solid hoofs. Now even with the differentiae capable of this specific subdivision it is difficult enough so to make the classification that each animal shall be comprehended in some one subdivision and not in more than one (e.g. winged and wingless; for some are both — e.g. ants, glowworms, and some others); but far more difficult, impossible, is it to do this, if we start with a dichotomy into two contradictories. For each differentia must be presented by some species. There must be some species, therefore, under the privative heading. Now specifically distinct animals cannot present in their substance a common undifferentiated element, but any apparently common element must really be differentiated. (Bird and Man for instance are both Two-footed, but their two-footedness is diverse and differentiated. And if they are sanguineous they must have some difference in their blood, if blood is part of their substance.) From this it follows that one differentia will belong to two species; and if that is so, it is plain that a privative cannot be a differentia.” (Complete Works, Barnes ed., vol. 1, p. 1000).

Aristotle’s positive conclusion is as as follows:

“We must attempt to recognize the natural groups, following the indications afforded by the instincts of mankind, which led them for instance to form the class of Birds and the class of Fishes, each of which groups combines a multitude of differentiae, and is not defined by a single one as in dichotomy. The method of dichotomy is either impossible (for it would put a single group under different divisions or contrary groups under the same division), or it only furnishes a single differentia for each species…. As we said then, we must define at the outset by a multiplicity of differentiae. If we do so, privative terms will be available, which are unavailable to the dichotomist” (pp. 1001-1002, emphasis added).

This is consistent with Plato’s more general advice that classifiers, like butchers, should “cut at the joints”, i.e., look for natural distinctions rather than imposing artificial ones. Dipping back again to the negative argument, Aristotle adds:

“Now if man was nothing more than a Cleft-footed animal, this single differentia would duly represent his essence. But seeing that this is not the case, more differentiae than this one will necessarily be required to define him; and these cannot come under one division; for each single branch of a dichotomy end in a single differentia, and cannot possibly include several differentiae belonging to one and the same animal.”

“It is impossible then to reach any of the ultimate animal forms by dichotomous division” (p. 1002; see also Classification; Hermeneutic Biology?.)

Observing Reason

Hegel had suggested that a Fichtean idealism ends up attempting to fill out its extreme abstraction by ad hoc adoption of a complementary Lockean empiricism. He goes on to treat something like Lockean empiricism, under the title of “Observing Reason”. The bulk of Hegel’s discussion ends up focusing on the empirical study of organic nature, with brief remarks on attempts to define psychological “laws of thought” and other psychological “laws”. Then he turns to physical anthropology, polemicizing at length against the old pseudo-sciences of physiognomy and phrenology, which purported to make predictions about human character from body types and skull shapes. Here we also reach the end of the first volume of Harris’ commentary on the Phenomenology, subtitled “The Pilgrimage of Reason”. The concluding second volume will be “The Odyssey of Spirit”.

Hegel dwells at length on the concept of organism, taking up Kant’s practical vindication of Aristotelian teleology in biology. The unity of an organism has to do with a pure “purpose” internal to the organism. None of its particular observable characteristics turn out to be essential in themselves; rather, they all have a fundamentally relational character. In Force and Understanding he had argued that mathematical physical law is purely relational; here he treats an organism as a purely relational unity held together by an internal “purpose”. Force and Understanding had been concerned with the formal unity of the physical world; the notion of organism introduces the notion of individuation within a world. Hegel picturesquely says that animals actively individuate themselves — distinguish themselves from the surrounding world — by means of their teeth and claws. By comparison, plants in their “quiescence” have only a minimal kind of individuality. Previously, he had quipped that animals must be unimpressed by the putative separateness of objects, because without ceremony they fall to and gobble them up.

Harris says in his commentary, “Observing Reason is a ‘return’ of Sense-Certainty and Perception together, because it is concerned with the ‘essence’ of real things. It wants to conceptualize them, but it is naive, like the Understanding” (Hegel’s Ladder I, p. 474).

“Locke’s standpoint differs from that of Sense-Certainty and Perception, both because he insists that the mind can know only its own ideas, and because what he calls the ‘plain historical method’ is a descriptive technique that aims to uncover the universal laws and principles of rational epistemology” (p. 475). The world is “stripped” to the pure concept of “matter or extension” (p. 476). “Here at the beginning we are faced by a Reason that wants to know not itself, but the world of things” (p. 477).

In the context of organic nature, “[Hegel] is now going to show us that the Kantian concept of mathematical schematism (which is a direct descendant of Gailleo’s distinction [between primary and secondary qualities of bodies]) fails completely as a bridge between the observed data and the conceptual structures used by the scientific ‘observers’. The observing consciousness of Reason itself is now going to learn what we learned when we observed the perceptual consciousness. It will learn that the thing is a Hegelian concept, (not a Galilean or Lockean one). The consciousness we are observing will discover that the [Galilean or Lockean “thing”] cannot correspond to Reason because it is essentially and necessarily dead” (p. 478).

(I confess I don’t recognize the reference to Kantian “schematism” as mathematical; I think of Kantian schematism more generally as a mediation between sensible “intuition” and conceptual thought through imagination.)

“Everywhere it observes things; but what it seeks is their Concept, or the law of their behavior…. It will observe first the natural world, then itself (as subjective spirit); and finally it will observe the relation between subjective spirit and its natural embodiment. But because the object of observation must always be a stably inert Gestalt, an observable thing, the results achieved become less satisfactory at every step” (pp. 478-479).

“[T]he ‘immediacy’ of the standpoint means that we are not observing it in the proper way…. Consciousness must first descend ‘into its own depth’. Thinking must discover what it is, as an activity; it must discover the dialectical logic that is its own ‘living spirit'” (p. 479). But this is only a beginning.

“The logical priority of ‘consciousness’ as the ‘own proper shape’ of Reason can only be established by the reductio ad absurdum of the alternate route through ‘things’. It must be established in this way, because the structure of ‘consciousness’ determines that Reason will naturally begin by trying to find itself in ‘things’…. Hence it is part of the object of the present chapter to show that we cannot make a direct descent into the depths of consciousness as subjectivity. If we try to do this (as Kant and Fichte did) what we discover is only an abstract essence of Reason that is perfectly valid, but almost completely useless. Its only real use will be to serve as the guiding light for the subsequent descent into the depths of our cultural world. We have to experience both the quest for the ‘essence of things’ and the quest for the ‘essence of consciousness’ before we can properly embark upon the discovery of the self in its thing-world” (ibid).

Harris develops Hegel’s distinction between inert “representations” of “things” and active thought. “The controlling conception in Hegel’s mind is the self-individuation of the Aristotelian form” (p. 486).

In this context of organic nature, Harris notes Hegel’s general preference for Plato and Aristotle over Newton, and thinks Hegel also takes from Aristotle the less fortunate view that nature has no history. I take Aristotle’s remarks about the “eternity” of species, the motions of the stars, etc., as having the valid pragmatic sense that such things had not been observed to change within living social memory. (I note also that Plato in the Laws already suggested that organic species do in fact come to be and perish.) Hegel defends Aristotelian “internal” teleology, while rejecting both the biological mechanism of Descartes and the “external” teleology of the argument from design used by Newton and others. Purposefulness for Hegel does not presuppose a mind (p. 502).

In spite of his criticisms of philosophical empiricism, Hegel defends the importance of empirical verification of hypotheses. Harris actually calls Hegel a “spiritual empiricist” in both natural science and ethics (p. 490). He says that Hegelian “necessity” is neither physical nor formal, but “logical” in Hegel’s sense. Hegel is much more concerned to criticize the “formalism” of philosophies of nature developed by followers of Schelling than actual scientific work.

In spite of the importance of “Life” in contrast to “dead” things in Hegel’s view, he has no use for vitalism. “Life is not more on the ‘inside’ of the organism than it is on the ‘outside’…. It is the ‘general fluidity’ within which the parts and organs of the body are formed and dissolved…. Observing Reason makes the Newtonian mistake of granting priority to visible stability” (p. 507). Hegel discusses notions of “sensibility” and “irritability” current in the biology of his time, adding in his own notions of “fluidity” and “elasticity”. He is very skeptical about “laws” in biology.

Between remarks on zoology and psychology, Hegel briefly (and dismissively) discusses so-called “laws of thought”. These relate to the early modern tradition of psychologizing in logic. With somewhat different motivation, Hegel anticipates Frege and Husserl’s rejection of such “psychologism”.

He also has no use for early modern psychology. In Harris’ summary, “Observational psychology operates with a mechanical toy that is all in pieces, so that the soul is observed and discussed like a bag full of loose bits” (p. 562). Hegel adds some sympathetic remarks on biography before launching a devastating critique of the now-forgotten pretensions of physiognomy and phrenology to discern purely physical indications of human character. What is important in the last is his general contention that even animal behavior cannot be adequately explained in a purely mechanistic way.

In spite of all of this, the idea of “observing” the objective dimension of a self in its concrete actualization in the world as contrasted with any direct intuition of pure interiority will turn out to have pivotal importance in the development to come. This is in fact how we experience others, and how others experience us. For Hegel it is our shared experience of one another rather than anyone’s private experience that is the basis of ethics. (See also Individuality, Community.)

Biological Diversity

Modern biology provides an abundance of empirical evidence that things like populations and ecosystems need diversity to flourish. Inbreeding leads to all sorts of genetic defects; monoculture crops and other simplified environments are more vulnerable to pests, and generally far less able to recover on their own when disturbed.

In a more reflective, interpretive vein closer to ordinary experience, Aristotle already documented the tremendous variety exhibited in nature. Species are not somehow pre-given, but rather to be discerned and understood in terms of specific ways of meeting very general needs.

The fact that there is a superabundance of such ways in nature is one of the most basic observations we can make. Nature as we concretely experience it is much more characterized by this superabundance and diversity than by univocal necessity of the kind we find in mathematics. For Aristotle, an emphasis on this superabundance and diversity goes hand-in-hand with a perspective that looks to purely natural ends and means as more primary in the order of explanation than mechanical metaphors.

This suggests a broader paradigm of intelligibility, reason, and objectivity than the one grounded in mathematics, univocity, and simple necessity. Emotional reasonableness is a real thing that is not at all reducible to formal logic. Similarly, intelligibility, reason, and objectivity in general have a practical reality that should not be understood as requiring a univocal foundation. (See also Bounty of Nature; Equivocal Determination; Multiple Explanations.)

Hermeneutic Biology?

Aristotle’s biological works are quite fascinating and lively. They contain abundant experiential reports, including some hearsay, intermixed with thoughtful reflection. Ultimately it is the reflective aspect that gives them their enduring value.

Sometimes, the content is surprising. For instance, book 1 of Parts of Animals is the place where he thoroughly criticizes the notion of classification by dichotomy. With concrete illustrations from the animal kingdom, he shows that commonly recognized kinds cannot be arrived at by successive dichotomous distinctions. Aristotelian distinction is n-ary rather than binary, pluralist rather than dualist.

Elsewhere (Metaphysics 982b) he famously said that philosophy begins in wonder. At Parts of Animals 645a, he added, “We therefore must not recoil with childish aversion from the examination of the humbler animals. Every realm of nature is marvelous: and as Heraclitus, when strangers who came to visit him found him warming himself at the furnace in the kitchen and hesitated to go in, is reported to have bidden them not to be afraid to enter, as even in that kitchen divinities were present, so we should venture on the study of every kind of animal without distaste; for each and all will reveal to us something natural and something beautiful. Absence of haphazard and conduciveness of everything to an end are to be found in natures’s works in the highest degree, and the end for which those works are put together and produced is a form of the beautiful” (Complete Works, revised Oxford edition vol. 1, p. 1004; see also Natural Ends; Sentience).

Natural Ends

Early modern science sought to banish consideration of ends from the empirical world, in favor of purely mathematical and factual description. Kant recovered a heuristic use of teleology, especially in biology (see Kant’s Recovery of Ends), and numerous more recent biological researchers have followed suit.

It is relatively easy to see that any kind of desire (say on the part of an animal) is a desire for something that is usually more general than a concrete object that satisfies the desire. More broadly, living things can also plausibly be said to have indwelling tendencies of nutrition and reproduction.

The case of inorganic nature is a bit more challenging for us to understand this way, but where modern science sees abstract mathematical-physical laws in operation, the effect of which may be modified by various circumstances, Aristotle saw concrete material tendencies for things to develop in certain ways, subject to similar modifications. At a certain level of abstraction, observable material tendencies can be viewed as “moving” things in a way broadly analogous to desire. The heavy object “wants” to fall. This just refers back to the observed fact that heavy objects have a tendency to fall, when not impeded by something else. At a level of common-sense interpretation of experience, this does not lead to any false conclusions.

There is no reason why the mathematical-law description and the material-tendency description cannot coexist. The predictive power of mathematically formulated laws makes them invaluable for engineering applications. But for ordinary life, what we are usually interested in are qualitative distinctions that have practical significance.

Thus, in addition to rational ends, there seem to be three kinds or degrees of natural ends or endlike things: ends of desire; primitive vital ends; and endlike tendencies associated with Aristotelian matter of various kinds and descriptions. (See also Ends; Aristotelian Matter.)

The Animal’s Leg Joint

In De Motu Animalium, Aristotle says there is an unmoved mover in the animal’s leg joint, and proceeds to a geometrical description of the axis of rotation of the joint. More famously, he says there are unmoved movers in the apparent motion of the fixed stars and planets, and there too associates them with geometrical axes of circular motions. What is going on here? This is a good illustration of several points.

First, Aristotle is perfectly happy to use mathematics in natural science. (He just correctly judged that early Greek arithmetic and geometry generally had little to contribute to the intelligibility of becoming, and wisely objected to the Pythagorean numerology that found a place in the Platonic Academy.)

Second, there is nothing mysterious about what he calls an unmoved mover. In the best-known cases, it refers to something that is in fact not only observable but mathematically describable. (This is not the only way a concept can have value, but that is not the point here.)

Third, he calls the unmoved mover a “mover” in the sense that it is the descriptive law or form of the physical motion in question, not a driving impulse or force. In a similar move, Leibniz famously said God is the law of the series.