In the Sophist, Plato asks how there can be false statements. A false statement (logos) says what is not. But a statement cannot say nothing – there must be something that it says. Plato tries to solve the puzzle by investigating the notion of not-being and the notion of a logos. To understand not-being, we must first understand being. That in turn requires understanding how something can be called by many different names. Plato’s solution to these problems rests on the distinction between what something is of itself and what it is because it is related to other things. It also rests on an understanding of the notion of difference. The class of not-beautiful things, for example, is a real group: they are different from the beautiful things. Similarly, not-beings are a real group. The upshot is this: “Theaetetus is flying” is false, in that flying is different from what is with reference to Theaetetus. Theaetetus has being. Flying has being. But “Theaetetus is flying” says with reference to him what is not.