  At 145d Socrates states the “one little question that puzzles” him: “What is knowledge?” Theaetetus’ first response (D0) is to offer examples of knowledge (146c).  Socrates rejects this response, arguing that, for any x, examples of x are neither necessary nor sufficient for a definition of x. They are not necessary, because they are irrelevant (146e). They are not sufficient, because they presuppose the understanding that a definition is meant to provide (147a–b). Moreover (147c), a definition could be briefly stated, whereas talking about examples is “an interminable diversion” (aperanton hodon).