 A reflection on the meaning of Socrates’ quest for definitions in the early dialogues suggests that Plato cannot have been blind to the sterility of a purely negative way of argument, or if he was blind at first, his blindness cannot have lasted long. For Socrates’ quest for definitions has important consequences. First and foremost, definitions presuppose that there is a definable object; that is to say, that it must have a stable nature. Nothing can be defined whose nature changes all the time. In addition, the object in question must be a unitary phenomenon, even if its unity may be complex. If definitions are to provide the basis of knowledge, they require some kind of essentialism. This presupposition is indeed made explicit in the Euthyphro, where Plato employs for the first time the terminology that will be characteristic of his full-fledged theory of the Forms. In response to Euthyphro’s enumeration of various examples of pious behavior, Socrates demands an account of the one feature (Euthphr. 5d: idea; 6d: eidos; 6e: paradeigma) that is common to all cases of what is holy or pious. Despite this pregnant terminology, few scholars nowadays hold that the Euthyphro already presupposes transcendent Forms in a realm of their own– models that are incompletely represented by their imitations under material conditions. The terms eidos and idea preserved their original meaning of ‘look’ or ‘shape’ into the classical age; but they were also often used in the more abstract sense of ‘form’, ‘sort’, ‘type’, or ‘kind’. No more than piety or holiness in the abstract sense seems to be presupposed in the discussion of the Euthyphro. There is, at any rate, no mention here of any separation of a sensible and an intelligible realm, let alone of an existence of ‘the holy itself’, as an entity existing in splendid isolation from all particular cases of holiness.