The Dialogues of Plato (427-347 B.C.) rank with the writings of Aristotle as the most important and influential philosophical works in Western thought. In them Plato cast his teacher Socrates as the central disputant in colloquies that brilliantly probe a vast spectrum of philosophical ideas and issues. None are more exciting and revelatory than the four dialogues - Euthyphro, Apology, Crito and Phaedo - on themes evoked by the trial and death of Socrates, accused by his enemies and detractors of crimes against the state, among them "impiety" and "corruption of the young." In Euthyphro, Socrates explores the concepts and aims of piety and religion; in Apology he courageously defends the integrity of his teachings; in Crito, he demonstrates his respect for the law in his refusal to flee his death sentence; and in Phaedo embraces death and discusses the immortality of the soul.