The Discovery of chreia: Galen’s Method of Teleological Demonstration and Its Aristotelian Background

The paper explores Galen’s notion of the chreia of bodily parts and activities, and the method of its discovery against the Aristotelian background. It argues that the chreia of an object π (a bodily part or activity) is a connection between the activity ε for the sake of which π has come into existence, and the attributes of π without which ε would cease to exist or would not be as good. The discovery of chreia, then, is an explanation of this connection. Aristotle does not use the word ‘chreia’ in this sense, but in Parts of Animals he employs a partly overlapping notion which he calls ‘ergon’. Finally, the paper points out that Galen’s chreia is equivalent to the middle term of teleological demonstrations, as outlined in Aristotle’s Posterior Analytics II 11.