Pla·to \'plat-(.)o\. Orig. name Aris·to·cles \e-'ris-te-.klez\. c.428-348 or 347 B.C. Greek philosopher. Surnamed Plato because of his broad forehead or wide range of knowledge. Disciple of Socrates and teacher of Aristotle, with them laid philosophical foundations of Western culture. Studied under and with Socrates until Socrates' s execution (399 B.C.), then left Athens; stayed for a while in Megara; traveled in Egypt, Cyrene, Sicily, and Magna Graecia. Returned to Athens permanently (387) and there founded his school of philosophy known as the Academy. His extant works are in form of dialogues, in each of which his master, Socrates, is represented in a leading role; these dialogues include Republic (generally regarded as his greatest work; a search for justice in construction of an ideal state), Laws (on same theme; unfinished), Symposium (on ideal love), Phaedrus (attacking prevailing conception of rhetoric), Timaeus (embodying a theory of the universe and containing story of the lost Atlantis), Apology (purporting to give Socrates' s speech in own defense at his trial), Phaedo (on immortality of the soul; purporting to be a record of Socrates' s last conversation before death), also Charmides, Cratylus, Critias, Crito, Euthydemus, Euthyphro, Gorgias, Ion, Laches, Lesser Hippias, Lysis, Menexenus, Meno, Parmenides, Philebus, Politicus, Protagoras, Sophist, Theaetetus.