Socrates makes the claim that wisdom consists in knowing that one does not know in the Apology, and this same dialogue makes it clear that this claim is made in the context of the question of how a human being becomes a good human being. First of all, he is on trial for being a person who runs human beings through a process that makes them evil, but he also explains that he has spent much of his life considering the question of what sort of process or curriculum might make a person good. As he says in Apology (and repeats throughout the dialogues) though we know the process by which a horse becomes a good horse (they are sent to the trainer) and we even have a pretty good idea of the curriculum and procedure by which a body (or a sick body) becomes a healthy body (the Greeks knew well enough about gym training, healthy cooking, and medical treatment) we don’t know the process that we can run a person through to turn him from a man to a good man. There is something about the very idea of becoming a good person which is repugnant to seeing it as nothing but the result of being run through a system. Put the Socratic problem to yourself: do you know how to make a person good? Can I send a person to you and expect to get them back as virtuous? We all might have fragments of an idea of what is necessary, but no one lays claim to the insight that this would require, still less that they would have the power to execute the result. Seen in this light, the Socratic claim is uncontroversial and even obvious: of course we don’t know how to just make a person good. But why is this wisdom? And if we recognize it, why can we say we know nothing?
The simplest answer is that the our ignorance of how to become good (or the powerlessness in the face of our awareness) casts a shadow over everything we do. The shadow obscures things more and less, but anything we do is something we are doing with our life, and “what we should do with our life” is precisely the point of obscurity. This obscurity cannot be kept from spilling over into the things of the world: If the question of whether anyone should be a poet is obscure, then what am I to make of poems? If I don’t know what is good to teach, how clear can I be about what is good?
And so there is more than one response to the Socratic problem, but the fact at the bottom of it is beyond doubt: we have no school or set of trainers we can send persons to and expect them to come out as good persons, and it counts as wisdom to recognize this.
The perplexity of the human situation makes men naturally reach out for something greater than their individual selves, and in such circumstances human beings will always reach out to the divine, though at various points in history (and especially in contemporary times) they are encouraged to reach out to the powers of a collective (like a nation, or a race, or a spirit of the age, or a group of scientists in the future.) Socrates, however, recognizes problems even in this reaching out for something higher. Before coming into court to defend himself, he had an argument which concludes to his bewilderment on the question of how the human good relates to powers above humans. Our own lights are dim and this dimness includes even what it would involve to reach out to a brighter light. Philosophy can neither light our way nor illumine the ways of that greater reality that might lead us. That certainly deserves to be called “knowing nothing”.