As traditionally interpreted, Socrates in Plato's early dialogues believes virtue is practical wisdom, valuable primarily as a means to happiness, but he has little or nothing to say about what constitutes happiness. I defend a novel interpretation on which Socrates believes happiness consists in being virtuous and virtue is philosophical knowledge. My interpretation makes better sense of all of Socrates' claims. ;Chapter I introduces the exegetic problem and summarizes my solution. Chapter II shows that virtue in Plato's Euthydemus is knowledge (...) of good and bad. It also shows that the value Socrates attributes to it there is instrumental. However, though Socrates does argue that virtue is necessary for happiness, he does not consider it instrumentally sufficient for happiness. ;In the Apology and Crito, however, Socrates claims that virtue is sufficient for happiness and that it cannot be taken away, as Chapter III shows. I argue that the sufficiency-claim comes from Socrates' belief that virtue's intrinsic value makes its possessor happy, supporting this with other evidence from the Apology and Crito. Based on this evidence, I conclude that virtue is for Socrates the sole intrinsic good. ;Chapter IV shows that Socrates thinks he possesses knowledge of good and bad. Socrates expresses a paramount desire to philosophize, even after death if possible; he must therefore expect that philosophizing will yield further results. Given that virtue is Socrates' sole ultimate end, I conclude that virtue in Plato's early dialogues consists in philosophical knowledge, including but not limited to knowledge of good and bad. ;Chapter V shows that Socrates' belief in the invulnerability of the virtuous cannot be fully explained unless he believes that death cannot take away one's knowledge. I show that Socrates' claims about death in the Apology and Crito uphold this interpretation. I also show how my interpretation of Socrates' views about death can be used to corroborate Chapter III's main conclusion. ;Tying together Socrates' views on virtue, death, and philosophy, Chapter VI explains Socrates' belief that injuring others injures the agent: By diminishing one's pool of potential interlocutors, injuring others fails to maximize one's philosophical knowledge. (shrink)