In ‘Plato’s Euthyphro: An Analysis and Commentary’ (33), Peter Geach attributes two assumptions to Socrates which he calls the ‘Socratic Fallacy’ since its locus classicus is the early Socratic dialogues:
(A) if you know you are correctly predicating a given term ‘T,’ you must ‘know what it is to be T’ in the sense of being able to give a general criterion for a thing’s being T;
(B) it is no use to try and arrive at the meaning of‘T’ by giving examples of things that are T.
Geach claims that (B) follows from (A) because assuming (A) is true, one cannot know that an instance of T is really an instance of T unless one already knows ‘what T is.’ Hence, examples will not help in the search for a definition. (A) can also be called ‘the priority of definition principle’ because it essentially claims that one must know the definition of a term before one can know anything about that term.
The attribution of this ‘fallacy’ to Socrates has provoked many scholars to come to his defense: Vlastos, Santas, Beversluis, Woodruff, and Nehamas, for instance, deny that the Socratic Fallacy can be found in the dialogues (although they have varying formulations of precisely what it is that Socrates does not say). Most recently, William Prior argues that (A) does in fact occur in the dialogues, but rather than being a fallacy it is ‘a perfectly innocent consequence of Platonic epistemology.’ That is, for Plato, to have ‘knowledge’ or episteme that something is T does require having a correct definition of T. Prior argues that this is a reasonable demand in the case of ethical terms such as ‘courage’ and ‘virtue’ and that Geach sees this as a fallacy only because he assumes a Wittgensteinian conception of knowledge in which ‘meaning is use.’
I agree with Prior that Socrates does endorse (A) and that (A) is a consequence of Plato’s epistemology. But I shall argue that Socrates ’ adoption of (A) leads to problematic consequences which Plato cannot accept and which he attempts to evade. Thus I argue for a developmental thesis. In the early dialogues Plato via the character of Socrates makes many claims which together suggest that he holds (A) to be true. At this stage of Plato’s philosophical development he cannot successfully define any ethical term T and the consequence of this combined with (A) is that he cannot know anything about T. This consequence commits Plato to a serious form of skepticism at this point. In the Meno, a transitional dialogue in which Plato’s own views begin to replace those of Socrates, Plato still assumes (A) to be true but Meno’s Paradox (80de) for the first time indicates explicit consciousness of the consequences of (A): how can one even search for something one does not know at all? Plato’s response to this question—the doctrine of recollection and then, in the Phaedo, the transcendence of the forms—is his way of avoiding the skepticism to which Socrates is committed.
In section II, I shall survey the evidence for (A) in the Socratic dialogues, for I do believe it can be found there, pace Vlastos et al. Then, in section III, I shall argue that the Meno is the precise point at which Plato recognizes the problematic consequences of (A) and offers a multi-dimensional solution to this problem.
Sakezles, Priscilla, "The Socratic Fallacy in the Early Dialogues" (1999). The Society for Ancient Greek Philosophy Newsletter. 455.