I think that this comment about truth is also about aesthetics, but you can judge. I am currently teaching Plato's Apology and found myself thinking that Socrates really has a very different idea of truth, just as he has a very different idea of knowledge and wisdom. Let's say that his view of truth is not a correspondence, coherence or even pragmatist theory, although perhaps closest to pragmatist. I will call it an existentialist theory of truth. It is closely tied to his theories of knowledge and wisdom. There is an odd tie as well to the implicit theory of truth offered by Protagoras in the two sentences we have from him via Diogenes Laertius. I am thinking appeal to existential truth might be called aesthetic because existentialism focuses on the personal and the inner in the way that good art often, or maybe even always, does. Protagoras says that man is the measure of all things. Plato in the Theaetetus interprets this to mean that the individual is the measure of all things. (I know that the conventional view is that Plato and Socrates both saw Protagoras as wrong. I am questioning this.) This is taken the most to be an advocacy of relativism. Let's say that there is a sense in which the individual IS the measure, the sense in which the truth comes home to the individual and becomes meaningful to the individual as their own. Perhaps what is being said by Socrates is that yes the individual is the measure in the sense that existential truth (deep, meaningful truth, truth that is not just based on conventional definitions of terms) is a matter of a identification between self and other whereby whatever sentence is deemed to be true is not such simply because it corresponds to some fact but rather because it reveals a deep sympathy between self and sentence or self and concept, i.e. in a way that makes the sentence a living truth for the self. The constant return to "What is?" with regards to each concept of philosophical concern is the path to wisdom in this sense. (Knowledge based on scientific method is of course not of any less value. It is just not what we are getting at when we ask the "What is" question in a philosophical way.) Rather than rely on correspondence or coherence one is relying here on the Socratic daemon, i.e. the aspect of one's self which is able to intuit existential truth after long debate and dialogue, a truth, the having of which, is nothing other then the wisdom that Socrates deemed the only possible wisdom for humans. That wisdom is not simply knowing the extent one is ignorant but rather a wisdom that arises out of taking a questioning approach to conventional "wisdom" recognizing that a search for philosophical or existential truth will, through rigorous dialogue and debate, yield deeply personal results, actually yield virtue.
