Petter Sandstad (University of Rostock): Change, hylomorphism, and mereology

Parmenides argued for the impossibility of change: there is only being and non-being, but no change from one state into the other state. Both Plato and Aristotle argued against this Parmenidea view – here I will restrict my discussion to Aristotle.

For accidental change, Aristotle accounts for the possibility of changing, in that x maintains its form. For instance, Socrates can change from being white into being tanned, since Socrates throughout this process maintains his form (i.e., he continues being a human). For substantial change Aristotle requires another answer, because substantial change involves loss of form. For instance Socrates takes hemlock and dies, or wine turns into vinegar. In these cases, Aristotle holds that something else remains through the process of change: the underlying matter of the thing. To sum up, Aristotle holds that accidental change is possible when a thing maintains its form through the process of change, and that substantial change is possible when a thing maintains its matter through the process of change. Taken together, these seem to imply that Aristotle’s answer presupposes hylomorphism, the doctrine that substances are composed of matter and form.

In this talk I argue that Aristotle had the resources needed for a non-hylomorphic account of change. Instead, I make use of Aristotle’s mereology. This alternative has fewer and less controversial presuppositions: it is less controversial to say that x has a form and has parts, than to say that x is a hylomorphic compound of form and matter.

The difference lies in the account of substantial change. On the alternative account, which Aristotle could have defended (but probably did not), x can lose its form because one or more of its independent parts continues existing throughout the process of change. For Aristotle, many parts are dependent upon their whole (here Aristotle prefers “meros” ), but some are independent from their whole (“stoicheion”). For instance, the elements composing Socrates are independent from Socrates, while Socrates’ hand and Socrates’ whiteness are both dependent upon Socrates. By connecting Aristotle’s account of the possibility of change with mereology (and disconnecting it from hylomorphism), we get an account with more applicability to and relevance for contemporary discussions. And our contemporary theories of mereology can enrich Aristotle’s discussion of change.


This lecture was given on Thu, 1 July 2021, 14:40 (UK time) as part of the workshop Change and Changemakers in Ancient Philosophy. The workshop is a collaborative initiative of the Change and Changemakers Network (Siegen) together with the Mereology of Potentiality Project (Oxford).