Aristotle on Definition (review)

Ever since Socrates went about Athens asking his fellow citizens to define moral virtues, the importance of definitions to philosophical discourse has never waned. In volume 109 of Brill's Philosophia Antiqua Series of Studies on Ancient Philosophy, Marguerite Deslauriers offers a 'surprisingly quiet' reconstruction of Aristotle's theory of definition. The reconstruction focuses mainly on Aristotle's extended discussions of definition found in book 2 of the Posterior Analytics, book 6 of the Topics, and books 7 and 8 of the Metaphysics.

Deslauriers begins her study with an examination of the method of division Plato employed to acquire an understanding of what something is - a statement of its essence. Aristotle's own theory of definition is shown to be a development and a modification of his predecessor's views in an effort to answer two fundamental questions: (1) What is an essence? (2) What guarantees the certainty of the principles of demonstrative science? Deslauriers' reconstruction of Aristotle's theory of definition in the rest of her book shows how he answers these two questions.

In chapters 2 and 3, the author undertakes an analysis of the relevant passages in the Posterior Analytics, whose second book clarifies the role of definition in demonstrative syllogism. Of the four types of definition recognized by Deslauriers, it is the 'immediate definition,' the one that gives an undemonstrable account of what a thing is, that emerges as most important. The immediate definition, which states the formal cause of a simple object, is of primary interest to Aristotle, Deslauriers argues, for he presumes it will serve as the foundation of demonstrative science.

In the last two chapters, Deslauriers first looks at definition and its object in the Metaphysics and then at the technical rules to be followed in stating the essence provided in the Topics. In the Metaphysics Aristotle is concerned primarily with the immediate definition and with establishing its unity. The immediate definition must be of the definable form - the formal cause - and it must conform to the structure of genus-plus-differentia(e). According to Deslauriers, the Topics shows some of the assumptions Aristotle held in his discussions of definition in the other two works. The genus and differentia(e) are shown to be prior to and more knowable in an unqualified or absolute way than the essence defined; they are thereby the cause of our knowledge of the essence. In short, Deslauriers argues that the structure and unity of the immediate definition depends on the simple object it defines and on the unity of the parts of the essence in the simple object. In turn, the certainty of the immediate definition of a simple item depends on the unity.

Deslauriers' intention is to make it clear that immediate definitions that can act as first principles of demonstrative science also give us knowledge of substance as essence; and they are able to give us that knowledge for the same reason that they are able to act as first principles: because the genus-plus-differentia(e) structure ensures both their unity and their certainty. The connections Deslauriers makes between Aristotle's discussions on definition in the logical works and that in the metaphysical work find their source inAristotle's belief that an understandingof the structure of definition and the appropriatemethod for establishing definitions will reveal the structure of essences. Ultimately, the significance of Aristotle's theory of definition 'resides in the ability of immediate definition to bridge the logical and themetaphysical,' because it is the only type of definition able to act as a first principle for demonstrative science and reveal substance to us.

This book contains awonderfully concise and precise argumentation. It shows, successfully I think, a consistency and coherence in Aristotle's views on definition, even though the three extended discussions are found in philosophically diverse contexts. The reader is left with a strong impression of the elegance of both Aristotle's theory on definition and Marguerite Deslauriers' reconstruction of it. Both merit due consideration.