Abstract

What is the nature or essence of a living thing? According to contemporary modal accounts a natural, i.e. essential, property of an entity x is a property that x cannot exist without or one that x possesses in all possible worlds where it exists. In Aristotle, given the way he introduces "nature" in the Physics, it is doubtful whether such a criterion spells out a sufficient or even a necessary condition for essential properties. This is because Aristotle determines the essential properties of a living thing by considering its nature as a principle of change that determines the generation of that thing as an efficient and a final cause, rather than relying on modal considerations concerning the identity of that thing. In this paper I examine Aristotle’s definition of nature as an inner principle of change in Physics II.1 and analyse his arguments for the claim that the nature of a living thing is its form. Although there is not perhaps one single and univocal concept of nature throughout the corpus, Physics II.1 offers valuable evidence, indicating one of the main directions Aristotle takes in his investigation of the natures of living things. I try to show that his arguments presuppose the identity between the developing living thing and the fully developed one, justified by the potentiality actuality distinction. This identity reflects a teleological understanding of what the nature of a thing is. I conclude that this teleological understanding of nature results in a radically different concept of essence from the one advocated by contemporary modal essentialists. The self-sufficiency of ends in nature guides Aristotle in assuming an inspired principle in his metaphysics of natural substance: the oneness of the driving force and its goal, namely, the oneness of the efficient cause and the final cause of a substance