“How nice it would be,” replies Socrates [in Plato’s Symposium], “if wisdom were the kind of thing that could flow from what is more full into what is more empty.”  This means that knowledge is not a prefabricated object, or a finished content which can be directly transmitted by writing or by just any discourse. 

When Socrates claims that he knows only one thing—namely, that he does not know anythig—he is repudiating the traditional concept of knowledge.  His philosophical method consists not in transmitting knowledge (which would mean responding to his disciples’ questions) but in questioning his disciples, for he himself has nothing to say to them or teach them, so far as the theoretical content of knowledge is concerned.  Socratic irony consists in pretending that one wants to learn something from one’s interlocutor, in order to bring them to the point of discovering that he knows nothing of the area in which he claims to be wise.

Yet this critique of knowledge, although it seems entirely negative, has a double meaning.  On the one hand, it presupposes that knowledge and truth, as we have already seen, cannot be received ready-made, but must be engendered by the individual himself.   This is why Socrates says in the Theatetus that when he talks with other people, he contents himself with the role of midwife.  He himself knows nothing and teaches nothing, but is content to ask questions; and it is Socrates’ questions and interrogations which help his interlocutors give birth to “their” truth.  Such an image shows that knowledge is found within the soul itself and it is up to the individual to discover it, once he has discovered, thanks to Socrates, that his own knowledge was empty…

On the other hand, in Socrates the point of view is wholly different.  Socrates’ questions do not lead the interlocutor to know something, or to wind up with conclusions which could be formulated in the form of propositions on a given subject.  Rather, it is because the interlocutor discovers the vanity of his knowledge that he will at the same time discover his truth.  In other words, by passing from knowledge to himself, he will begin to place himself in question. 

Pierre Hadot, What Is Ancient Philosophy?