Aristotle’s Concept of Nature

Stasinos V. Stavrianeas, University of Edinburgh

1. Introduction: Nature and Modality

How are we to define the nature of an object? Is the nature of an object what it cannot do without? Is the nature of an object what that object is? Or is the nature of an object determined by what it is developing into? 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. Let us name this criterion the survivability criterion. Recently Kit Fine has argued against this view because the survivability criterion fails to distinguish between properties that constitute the nature of x and properties that are merely consequences of it or necessary truths about the world. Fine’s claim is that the survivability criterion is not sufficient for determining the nature of x. His own solution is that it is the definition of x that provides a sufficient criterion for this determination. Fine’s solution has affinities with Aristotle’s concept of the nature of x being what is expressed by the definition of x. 1

1 Fine offers two alternative formulations of the rival modal account: “At its very simplest, it takes an object to have a property essentially just in case it is necessary that the object has the property. But there are two variants … One variant makes the necessary possession conditional on existence: an object is taken to have a property essentially just in case it is necessary that the object has the property if it exists. The other variant makes the necessary conditional upon identity: an object is taken to have a property essentially just in case it is necessary that the object has the property if it is identical to that very object.” Kit Fine, “Essence and Modality” [Essence] in Philosophical Perspectives, 8, Logic and Language (1994), 3–4. For a formulation of the criterion see also Graeme Forbes ‘Essentialism’ [Essentialism] in Hale & Wright A companion to the Philosophy of Language (Oxford, 1997), 516. Variants of this view are expressed in G. E. Moore’s ‘External and Internal Relations’,Proceedings of the Aristotelian Society (1919), repr. in Philosophical Studies (1922), and in Saul Kripke’s Naming and Necessity (Cambridge, 1980). For a detailed comparison between Kripke’s essentialism and Aristotle’s account of essences see Charlotte Witt, Substance and Essence in Aristotle (Ithaca, 1989), 180ff.. She argues that one of the key difference between the two accounts lies in the fact that Aristotle “determines what is essential not by reflecting on the identity of an individual but by considering how to define an individual” (Witt, Substance and Essence, 189). The modal conception of essential properties is equivalent to an understanding of essential properties in terms of the survivability criterion. Fine argues that modal concepts are insensitive to essentialist facts. Different sets of essentialist truths can give rise to the same set of modal truths. So essentialist facts about identity are not sufficiently determined by modal facts (a similar view is expressed by E.J. Lowe, in hisThe Possibility of Metaphysics (Oxford, 1998), 149). Fine’s solution is to replace the modal approach with the Lockean idea of real definition (see also Graeme Forbes, Essentialism, 530–31). The necessary properties that fall outside the scope of 28 Stasinos V. Stavrianeas

Some Aristotelian commentators raise doubts on whether the survivability criterion constitutes even a necessary criterion for picking out the natural or essential properties of an entity. 2 Although I will not engage in this controversy, I do take Aristotle’s concept of nature to be built on grounds independent of survivability. I believe that this holds even though it seems that there is not one single concept of nature used rigidly throughout the corpus. Rather Aristotle modifies or expands his uses, and redirects his focus in different works. Nevertheless, whether there is a unified concept of nature operative in the corpus, or, if nature is not univocal, what is the element that unifies its different uses, are questions that I will not pursue here. I will concentrate on a close examination of how the concept is introduced in the opening chapter of Physics II. Still I believe that the ideas and arguments introduced there indicate certain basic characteristics of the concept that play a pre-eminent role at least in the biological works. On this perspective, Aristotle’s concept of nature, and consequently of the essence of living things, offers a significantly different model from, and an alternative to, the modern accounts where modal (possible worlds) intuitions are decisive in understanding essential properties. I shall argue that Aristotle’s views in Physics II.1 concerning nature are not grounded on modal considerations. Aristotle distinguishes between something having a nature and something being according to nature. 3 Natures are givens in the world, and what derives from them is due to nature or is according to it. Necessity can belong to properties on either side of the ‘natural – according to nature’ divide. Natures are ontological primitives in the world, but the concept of “nature” is not a primitive; it affords a teleological analysis in Aristotle’s sys- tem. Natures are ends, and as such they are completion points of developmental processes. Natures are realisations and fulfillments of ends. More loosely, they are self-sufficient packages for the actualisation of ends, giving rise to the gen- eration of an entity-with-a-goal and concluding with the entity’s corruption, achieving the fulfillment of the goal along the way. On my understanding of

the essence include truths of logic and sparse or improper properties. Although Fine refers to the Aristotelian distinction between essential properties included in the definition and merely necessary ones, his definition is wider than Aristotle’s (Kit Fine, Essence, 2). Aristotle identifies the essence of x with the nature of x. But not everything that belongs to x by nature or according to nature is included in this nature. For evidence that a criterion equivalent to survivability is insufficient in Aristotle see Top. I.5 102a17ff., V.1 128b16–20, 128b34–129a5. 2 That the survivability criterion is not even a necessary condition in Aristotle has been proposed recently by Sheldon M. Cohen, in his Aristotle on Incomplete Substance [Incomplete](Cambridge 1996) 1–3, 157ff. Cohen puts forward examples from Aristotle’s elemental theory, according to which a portion of, say, fire may lose one of its essential properties without thereby ceasing to be fire (Cohen, Incomplete, 41–2). A similar skepticism is expressed in Daniel Bonevac ‘Constitutive and Epistemic Principles’ in Poznan Studies in the Philosophy of Science and the Humanities 71, (2000), 183–4. 3 Nature is identified with that which is self-generated. Properties that are not controlling this process of self-generation may follow from nature or be according to this nature but they are not part of the definition of that nature or essence.