Philosophy 100 Essential Thinkers

by Philip Stokes

Since Parmenides proposed that to think of something is to give it some semblance of existence, then one cannot think of anything that is truly ‘not’. It follows that one can only think of that which is. Now comes the second part of Parmenides’ deductive reasoning, the first known example of a formal deduction in the history of Western thought. For to think of anything that is implies the existence of something that is not. If something is green, it is not red, if something is a man, it is not a dog, a house is not a cart, and so on. But since by his previous argument Parmenides has shown that negative existential claims are impossible, it seems one cannot make positive existential discriminations either. To distinguish X from Y, is to say that X is not Y, precisely that which Parmenides claims is impossible. Therefore, one cannot logically discriminate between different things in the world. One can only say, Parmenides concludes, that everything is and hence, the true nature of reality – that which is – must be that of an undivided, homogenous, single entity.