It has been accepted since antiquity that one of the basic principles of the philosophy of Socrates was ‘virtue is knowledge’; that this was so is made abundantly clear by both Plato and Aristotle. It has also been assumed by scholars ancient and modern that Socrates, who believed that in this knowledge lay happiness, spent his life looking for it. In the early dialogues Plato represents Socrates as frequently professing either partial or total ignorance, but as always more or less confidently searching for the truth. The traditional interpretation continues with the belief that somewhere near the time of his first visit to Sicily Plato’s thought began to develop beyond that of his master, and that one of his first advances was his theory of knowledge by recollection, which he developed presumably because of dissatisfaction with Socrates’ ideas on how knowledge could be attained.