 Closely related to this is the discussion, in Posterior Analytics II.3–10, of the question whether there can be both definition and demonstration of the same thing (that is, whether the same result can be established either by definition or by demonstration). Since the definitions Aristotle is interested in are statements of essences, knowing a definition is knowing, of some existing thing, what it is. Consequently, Aristotle’s question amounts to a question whether defining and demonstrating can be alternative ways of acquiring the same knowledge. His reply is complex: