Aristotle on Definition (review)

Aristotle on Definition is an exceptional piece of scholarship. Its arguments are carefully justified, sophisticated, and far-reaching. Those interested in Aristotle's theory of definition will find this book a nice compliment to David Charles' Meaning and Essence. Whereas Charles examines Aristotle's theory of syllogistic definitions, Deslauriers focuses mainly on the concept of immediate definitions (the sort of definitions that function as first principles in a science).

It is impossible to do justice to the entire book. In what follows I shall attempt to isolate one of its main lines of argument to give the reader a sense of the book's content.

In chapter 2, Deslauriers draws our attention to four types of definition identified in the Posterior Analytics and sets out to explore the differences between them. She focuses on two basic kinds of definition, what she calls "syllogistic" definitions and "immediate" definitions. Syllogistic definitions are accounts that indicate what something is through a middle term and are formulated by rearranging the terms of a demonstrative syllogism, whereas immediate definitions express propositions that cannot be displayed in demonstrations. Instead, they are arrived at and displayed through division by genus and differentiae. According to Deslauriers, Aristotle's account of these two basic kinds of definition in AnPo. 2. 10 is based on a fundamental distinction he draws concerning the relation of the object of definition to its cause: the objects of syllogistic definitions (e.g., eclipse, thunder) are complex items in the sense that they have something else as their cause, while the objects of immediate definitions (e.g., human, god) are simple items that do not have distinct causes. Deslauriers shows that simple items must, in fact, have aitia. Aristotle's point is that they do not have aitia distinct from themselves (cf. AnPo. 93a3–6). Since a form is one kind of aitia, were it the case that simple items lacked causes, Aristotle would have to be understood as positing items with no form (56–57). Thus, both immediate definitions and syllogistic definitions involve stating the cause of the object of definition. The following chart summarizes the results of chapters 2 and 3:

Simple Items	Complex Items
Objects of immediate definitions.	Objects of syllogistic definitions.
Answer ti estin? Questions.	Answer dioti? Questions.
No aitia distinct from themselves.	Have aitia distinct from themselves.
Aitia is formal cause.	Aitia is efficient cause.
Definition cannot be displayed in a demonstration; arrived at and displayed through division by genus and differentiae.	Definition can be displayed in a demonstration; formulated by rearranging the terms of a demonstration in which the middle term is the aitia.

Deslauriers argues that immediate definitions (unlike syllogistic definitions) are necessary precisely because the relation between their objects and the cause of those objects is immediate. With simple items there is nothing distinct from the thing itself that acts as the cause of the connection between subject and attribute (AnPo. 2. 4 , 91a25–32). Because the causality and necessity of immediate definitions is non-derived, immediate definitions alone can function as first principles of a demonstrative science.

In the remainder of the book, Deslauriers tackles a number of issues arising from Aristotle's treatment of definition in the Metaphysics. For example, she argues that the Metaphysics discussion of definition is focused primarily on immediate definitions and that the investigation of substance in Metaph. Z 4–5 seeks to exclude from consideration the objects of syllogistic definitions, since they lack the requisite kind of unity (insofar as they have aitia other than themselves). One implication of this is that, strictly speaking, the objects of syllogistic definitions described in AnPo. 2 cannot be defined and hence syllogistic definitions are not definitions in the proper sense (118, 124).

Deslauriers also looks at the problem (raised in the Metaphysics) of how to construct immediate definitions that are able to represent the essence of natural bodies that necessarily include matter. She points out that the objects of immediate definitions are not "simple" in the sense of having no parts; the species essence, represented...