SOCRATES
We know a few things about Socrates.

1. Plato (427-347 BCE) was a younger contemporary and student of Socrates (470-399 BCE).
2. Socrates was the first truly systematic (Western) philosopher.
3. Socrates inspired Plato and other subsequent philosophers, including Aristotle (Metaphysics i 6, xiii 4) (who had some independent evidence about Socrates's views), and many Athenian youths, including the iconoclast aristocrats Critias and Alcibiades (associated with the Thirty Tyrants).
4. Socrates was brought to trial on charges of impiety and corrupting the youth of Athens, convicted, and executed in 399.
5. We have no record that Socrates ever wrote anything.

• Plato's Socrates is both paradoxical and ironic; Xenophon's is neither.
• Plato's Socrates may win arguments, but rarely persuades his opponent; Xenophon's Socrates persuades all those with whom he argues.
• Plato's Socrates is concerned primarily with human affairs; Xenophon's Socrates is concerned with theology.
• Plato's Socrates denies that one should ever harm one's enemies in flat contradiction of then conventional Greek (e.g. Homeric) moral views; Xenophon's Socrates never contradicts Greek popular morality.

SOCRATES AND PLATO
Attention to the content and style of Plato's dialogues and the testimony of Aristotle (Metaphysics i 6; xiii 4) allows us divide the dialogues reasonably well into four groups.

• Early or Socratic Dialogues
• Apology, Crito, Euthyphro, Laches, Charmides, Euthydemus, and Lysis
• Transitional Dialogues
• Protagoras and Gorgias
• Middle or Platonic Dialogues
• Meno, Phaedo, Republic, Symposium, Phaedrus, Parmenides, and Theaetetus
• Later Platonic Dialogues
• Timaeus, Sophist, Statesman, Philebus, and Laws

1. Moral Knowledge and Socratic Ignorance.  (a) Socrates seems to believe that we should expect to find expertise in matters ethical, as in other crafts (Cri 46c 47d); (b) yet he claims to be ignorant himself and believes that others know even less than he does (Ap 19c, 20c e, 21d, 33b); (c) yet he seems quite confident about some moral claims and is willing to rely on them in arguing with others (Ap 17bc, 28b, 29b, 41e).  Though (a) and (c) are consistent, both appear to conflict with (b).
2. Virtue and Happiness. Socrates believes that (a) an agent's own happiness (eudaimonia) is or ought to be the ultimate end of all of her action (La 181ce, 192d; Ch 169b, 173e; Eud 278e w/ 280b6, 282a), yet he believes that (b) familiar, other-regarding virtues (e.g. courage and justice) are admirable.  (a) and (b) commit him to other claims.  He believes that (c) one should be virtuous at any price (Ap 28b, 29b, 32bc; Cri 48cd, 49b).  In fact, Socrates believes that (d) virtue (e.g. temperance, justice, courage, piety, wisdom) is both necessary and sufficient for the agent's happiness (Ap 29b 30b, 30d, 36c, 41d e).  This implies that (e) a good person cannot be harmed (Ap 41cd) and that (f) one cannot profit by vice (e.g. injustice).
3. Virtue is Knowledge.  This cognitive account of virtue seems to imply several things: (a) that knowledge is necessary for virtue (La 192cd; Ch 159a), and by (1b), that no one is virtuous (because no one has the requisite knowledge); (b) that knowledge is sufficient for virtue (Ap 25c 26a, 37a), which implies that weakness of will is impossible (you can't know what virtue requires without acting virtuously); and (c) the unity of the virtues (La 199e), which implies that you cannot have one virtue without the others.