EUCLID (EucLEIDEs) (c. B.C.), founder of Megarian school of philosophy, born at Megara, and became a devoted disciple of Socrates. When a decree was passed forbidding the Megarians to enter Athens, he and his friends withdrew to Megara. It has been conjectured that this was the period of Plato's resi dence in Megara, of which indications appear in the Theaetetus. He is said to have written six dialogues, of which only the titles remain. For his doctrine (a combination of the principles of Parmenides and Socrates) see MEGARIAN SCHOOL.