The Aristotelian Corpus

The works in the Aristotelian corpus are organized systematically, not chronologically. In contrast to the Platonic corpus, there is no chronological division into early, middle, and late works. (Some of Aristotle's works do appear less mature than others. The Categories is an example. It is both first in the corpus and appears to have been written before certain other works in the corpus.)

Plato and Aristotle, the School of Athens

The Aristotelian corpus subdivides into three main parts according to subject: the logical works, physical works, and ethical works. The logical works are first. They are followed by the physical works, which constitute the largest part of the corpus. The ethical works are last.

The Aristotelian corpus is composed of esoteric (as opposed to exoteric) works. They are written for members of his school. Many of these works are little more than a series of notes. They lack the explanation necessary for those who are not already familiar with the main lines of thought.

The approach to the Aristotelian corpus

The systematic organization and unfinished nature of works make it is hard to know the appropriate order in which to read works in the corpus. (This was not a problem with the Platonic corpus because the assumption was that Plato first writes to understand and vindicate Socrates. Given this assumption, it is natural to begin with the Apology and other dialogues in which Plato is working out the details of his understanding of what Socrates thought.) The approach to the Aristotelian corpus in this course is to begin with selected passages from the physical works. This has the advantage of placing Aristotle's thought in direct relation to Plato's and provides a way to see Aristotle as correcting what he regards as Plato's mistakes.

First and Second Philosophy

Aristotle calls the subject he pursues in the physical works "second philosophy" (or, more literally, the "love of wisdom secondarily" or "in a secondary way"). He understands second philosophy to approximate "first philosophy," and he understands first philosophy to be the legitimate offspring of Plato's conception of the life the lover of wisdom seeks as a life devoted to the "contemplation" (θεωρία) of the forms.

Aristotle's interest in "second philosophy" reinvigorates the philosophy of physics. This part of philosophy had emerged as part of the reaction to Thales and the Milesian inquirers into nature, but it was almost immediately pushed into the background when Socrates focused attention away from nature and onto ethical matters and the wisdom involved in living a good life and being "happy" (εὐδαίμων). Plato returns to the philosophy of physics in the late dialogues. In the Timaeus, which traditionally is thought to be a late dialogue, Socrates no longer leads the conversation. Plato has Timaeus take the lead and work out the beginnings of a conception of the reality of natural bodies in terms of forms. Aristotle works within the general outlines of the framework Plato has Timaeus set out, but at the same time Aristotle also tries to remove problems he sees in this framework. It is in this way that Aristotle is both the first great Platonist and Plato's first great critic.

(In Raphael's The School of Athens (part of which is depicted above), Plato is shown as pointing to a "higher" reality. Aristotle, in turn, is shown as countering this emphasis. He brings Platonism down from the heavens. He accepts what he regards as the central parts of Platonism, but he tries to eliminate what he regards as its excesses and outright mistakes.)

The Existence of Natural Bodies

Aristotle conceives of physics as the study of a certain kind of "being" or existence. This existence is the kind distinctive of natural bodies. Aristotle thinks that natural bodies possess a certain existence that distinguishes them as natural bodies. He understands this existence in terms of forms, but Aristotle conceives of forms differently from Plato. Aristotle conceives of the forms of natural bodies as particular objects. In the Metaphysics, as will become clearer later in the course, Aristotle thinks there are no general objects and perhaps that nothing general exists at all.

(We will consider what Aristotle thought about particular and general objects in more detail when we consider his ontology in the Metaphysics. The Metaphysics sits between the physical works and the ethical works. It is an exception to the three-part division of the corpus. It is also a work whose proper interpretation remains controversial. I give the Frede-Patzig interpretation.)

In thinking that natural bodies have a certain kind of existence, Aristotle sets himself apart from the inquirers into nature. In response to Parmenides, they rejected the existence of the ordinary objects in the traditional conception of reality because they thought that nothing comes into or goes out of existence. So, according to Democritus, only atoms and void are real. The various arrangements of the atoms in the void appear to human beings as natural bodies, but arrangements of atoms in the void are not themselves objects. They only appear as objects to those who rely on experience (as opposed to reason) to know what exists. Aristotle rejects this conception of the existence of natural bodies. He thinks that the natural bodies in the traditional conception of reality are real.

"Aristotle wants to hold on to the metaphysical primacy of objects, natural objects, living objects, human beings. He does not want these to be mere configurations of more basic entities, such that the real things turn out to be these more basic entities. But to look at an object just as the configuration of material constituents transiently happen to enter into is to look at the material constituents as the more basic entities. So since Aristotle, against the view of practically all his predecessors, wants to hold on to the ontological priority of objects, he introduces essences which guarantee this status" (Michael Frede, "On Aristotle's Conception of the Soul," 146-147).

Aristotle's conception of the existence of natural bodies in terms of forms is not easy to understand in complete detail, but his leading idea is relatively straightforward. He thinks that natural bodies have a certain unity that persists through time. He thinks that the material that constitutes a natural body is organized a certain way and thus has a certain organization. This organization is what makes the material be a natural body and hence one thing, as opposed to a heap of materials. It is in terms of forms that Aristotle explains what this organization and unity is.

Unity, Definition, and Demonstration

Aristotle supposes that the unity, or oneness, of a natural body is specified in a definition. This specification is the essence (or "what it is to be" (τὸ τί ἦν εἶναι)) of bodies of the kind. This essence figures in a "demonstration" (ἀπόδειξις). Definitions are among the starting-points for demonstration. The definition specifies the essence of the species of the natural bodies under consideration. Demonstrations are deductive arguments (syllogisms) that demonstrate that these natural bodies have their specific behaviors because these bodies instantiate the essence specified in the definition.

Aristotle discusses demonstration in the logical works.

Like the Aristotelian corpus generally, the logical works are organized systematically. The Categories discusses terms, the parts of sentences. The On Interpretation discusses sentences, the parts of syllogisms. The Prior and Posterior Analytics follow On Interpretation. The Prior Analytics discusses syllogisms, and the Posterior Analytics discusses demonstrations.

Aristotle's discussions of natural bodies in the physical works are investigations, not finished science, and so these discussions do not contain demonstrations. The following demonstration (which is based on the Aristotelian idea that rational animal is the essence of man) indicates what Aristotle seems to have had in mind:

Rational animals make discriminations in terms of sensation. (All M are P)
Human beings are rational animals. (All S are M)
Human beings make discriminations in terms of sensation. (All S are P)

(The terms in a syllogism are the "middle" (M), "predicate"(P), and "subject" (S) terms. Each of the premises has one term in common with the conclusion. In a major premise, this is the predicate of the conclusion. In a minor premise, it is the subject of the conclusion. It is customary to write the major premise first.)

This "syllogism" (συλλογισμός) displays some of the structure that belongs to bodies of the natural kind, human being. Each human being has a certain unity, or oneness, that persists through changes in the human being. This unity is specified formally in the definition of what a human being is. If the material has the organization of a rational animal, then the material is not just a heap. Rather, the material constitutes an enduring natural body. In particular, it constitutes a natural body with the power to make discriminations in terms of sensations. This power is a consequence of the organization of the material. The organization makes the material be a human being. A human being, as a rational animal, has the power to make discriminations in terms of sensations.

Physics is Second Philosophy

Now it is possible to see a little more clearly why Aristotle thinks of the subject he pursues in the physical works as "second philosophy."

If the organization specified in the definition is the form of the natural body, then the thinking in physics is an example of the "contemplation" (θεωρία) that is the thinking that, according to Socrates in the Phaedo, defines the life of the lover of wisdom. Physics is thinking about demonstrations, and thinking about demonstrations is thinking about forms.

(Socrates seems to have understood the "wisdom" (σοφία) in the "love of wisdom" (φιλοσοφία) as the knowledge involved in living a good life, but the term φιλοσοφία is more general in its meaning. In the Theaetetus, a late dialogue, Plato has Socrates tell Theodorus that if were interested in Cyrene and its affairs, he would ask "whether any of the young men there are devoting themselves to geometry or any other form of philosophy (γεωμετρίαν ἤ τινα ἄλλην φιλοσοφίαν)" (Theaetetus 143d). In the Timaeus, another late dialogue, Plato has Timaeus insist on the importance of "harmonics and every kind of philosophy (μουσικῇ καὶ πάσῃ φιλοσοφίᾳ)" (Timaeus 88c). In these passages, the σοφία in φιλοσοφία is a body of theoretical knowledge and φιλοσοφία is a discipline that aims to acquire such knowledge. This use of the term allows Aristotle to think of physics as a kind of "philosophy" (φιλοσοφία) whether or not he thinks that thinking about demonstrations is thinking about forms.)

This interpretation, however, does not show why Aristotle thinks of physics as "second" as opposed to "first philosophy." The idea, it seems, is that the objects of the study in physics are somehow secondary. Since the objects of the study are the forms of natural bodies, this means that these forms are somehow secondary. To get straight on what this means, it is necessary to take a closer look at what these forms are and also at Aristotle's ontology more generally. This is a large undertaking, and it will be an ongoing task in subsequent lectures.

Reason, Knowledge, and the Theory of Induction

Aristotle explains knowledge of the definitions that figure in demonstrations in a way that he thinks corrects a mistake in Platonism.

Like Socrates and Plato, Aristotle thinks of a human beings in terms of the "soul" (ψυχή). Aristotle and Plato both accept the broad framework of this Socratic understanding of human beings. Aristotle, however, rejects the Platonic idea (in the Theory of Recollection) that the human soul preexists the body and that human beings are born with knowledge. Aristotle thinks that human beings naturally come to possess the cognition he calls "reason" and the knowledge that belongs to "reason" through a teleological causal process that he calls "induction" (ἐπαγωγή). He thinks that human beings first have "reason" not when they are born but when they acquire certain basic concepts about the world and the knowledge that these concepts embody.

Aristotle theory of induction is not straightforward to understand. What exactly he has in mind is the subject of a subsequent lecture.

"Aristotle quite explicitly says (APo. B19.100a2) that reason only comes into being as we acquire the appropriate concepts of things and thereby the knowledge of things and their principles whose mastery of these concepts embodies." (Michael Frede, "Introduction" in Rationality in Greek Thought, 11.)

"Aristotle's own view seems to be that to recognize reason as something apart from perception would involve a recognition of the intellect (νοῦς) with its distinctive active power to grasp terms or universals and thus the basic terms and the immediate truths about them from which all other scientific truths can be deduced, a power which, though (at least in the case of human beings) causally linked to, and in a way based on, perception, nevertheless epistemologically is an independent source of knowledge, in fact the source of all knowledge properly speaking." (Michael Frede, "An Empiricist View of Knowledge: Memorism," 236.)

"In [Posterior Analytics] B19, the crucial word 'logos,' finally does occur, namely in 100a2. It is used to refer to precisely the disposition of the mind or soul in virtue of which, or perhaps rather in which, we know first principles, and he talks of this disposition as something we come to acquire. I infer from this, though the conclusion seems striking and surprising (given our intuitions about, and our understanding of, reason), that Aristotle assumes that we are not born with reason, but acquire it, and that, in Aristotle's view, to have reason, to be fully rational or reasonably, is know first principles." (Michael Frede, "Aristotle's Rationalism," 169.)