The justification of the existence of higher natures in the physics of Aristotle

Abstract

In his own era, just as today, Aristotle's doctrine of øύσιϛ was controversial. Against the materialist philosophers of his day, Aristotle sustained the existence of real actualities of a higher order than the "elements" or "atoms" postulated by these philosophers. This type of higher actuality or "higher" øύσιϛ is the form of a natural substance, which gives it a genuine unity beyond that of an aggregate of elements, and which acts as the source of the substance's characteristic operations. How does the Stagirite justify postulating such higher actualities? In this dissertation, I will examine the justifications that Aristotle gives, both explicitly and indirectly, in the Physics, the Metaphysics, On the Soul, On Generation and Corruption and On the Heavens, among other texts. I show that Aristotle's justification for asserting the reality of "higher" øύσιϛ derives from two sources. In the first place, his overall physical and metaphysical doctrines undermine the arguments adduced by the ancient Greek materialists in favor of reductionism, and make plausible the existence of higher øύσιϛ of the sort he proposes. Secondly, Aristotle provides a number of positive arguments in favor of the necessity of postulating higher actualities or øύσιϛ in order to explain the existence and activity of organisms. These arguments acquire substantially greater weight and cogency than is commonly acknowledged when viewed in the light of his metaphysical and physical doctrines.