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 how to approach the corpus. The approach 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.

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 conceives of first philosophy as the legitimate offspring of Plato's attempt to understand the love of wisdom as involving 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 on ethical matters and the good life for human beings. 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 work out the beginnings of a conception of the reality of natural bodies. 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 second philosophy 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 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. Given this understanding of natural bodies, the philosophical problem for Aristotle is to explain what this organization and unity is.

Aristotle is a Platonist. He tries to understand this unity in terms of forms. Further, although this is a matter of controversy, he seems to understand these forms as particular objects.

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 how the subject Aristotle pursues in the physical works is "second philosophy" and this is a kind of "philosophy" (φιλοσοφία).

If the organization specified in the definition is the form of the natural body, and if, as Aristotle supposes, forms are the reality of natural bodies, then the study of physics is an example of the "contemplation" (θεωρία) of forms that is central to the love of wisdom. The suggestion in Plato (in the Phaedo and elsewhere) is that the "contemplation" of forms in the love of wisdom is thinking about the reality of things. Physics, as second philosophy, is an example of this thinking. Holding demonstrations in mind is thinking about the reality of natural bodies.

This interpretation helps explain why second philosophy is a kind of philosophy (or love of wisdom), but several difficult questions remain.

First and foremost among these questions is why Aristotle thinks of physics as second philosophy 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 that human beings are psychological beings. 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.)