Date of Award

Spring 2021

Document Type


Degree Name

Doctor of Philosophy (PhD)



First Advisor

Goldin, Owen

Second Advisor

Taylor, Richard C.

Third Advisor

Bloch-Mullins, Corinne


In this dissertation I attempt to clarify Aristotle’s notion of essence. In particular, I focus on the essence of animal substances. When looking at Aristotle’s biological works and works like the Metaphysics it becomes perplexing how the accounts of animal essences in both are to constitute a unified view. In Parts of Animals the emphasis seems to be on definitions of animals that are rich enough to further explanatory aims. It is hard to see how such rich but messy definitions will be amenable to the strategies for a definition’s unity as are given in the Metaphysics. I argue that there is a consistent account of essence to be found. By bringing Aristotle’s discussion on essence from Parts of Animals I into his discussions of definitional unity in Zeta 12 and Eta 6, there emerge resources for dealing with the problems plaguing these two sections from the Metaphysics. The key is recognizing that Aristotelian animal essences are comprised of terms describing the animal parts and their functions in greater and lesser degrees of determinacy. I argue that there is a kind of closure of function among such animal parts, and this is the basis for the unity of a substance mentioned vaguely in Eta 6. The several differences in an animal’s definition reflect this functional closure by exhibiting a kind of explanatory closure. I then build upon recent work concerning the determination relation in Aristotle to show how the several genera and differences contained in the animal essence are a unity.

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