Megarian School of Ancient Greek Philosophy Texts

Eucleides (Euclid) of Megara, a pupil of Socrates, founded a school in his home city around 400 BCE. He began from the Socratic principle that ἀρετή is knowledge and joined it to the Parmenidean view that reality is one, unchanging, and eternal, standing apart from sense experience. For the Megarians the good was a single thing, called at turns wisdom, god, or reason, and they denied reality to its opposite.

The school's characteristic method was dialectic: rigorous question-and-answer disputation in defence of fixed theses. Its practitioners took whole propositions, rather than the predicates that Aristotle studied, as the unit of analysis, and they rejected the Aristotelian categories, the reality of motion, and any claim that what is merely possible but never actual has being. On their account only what is true now, or will be true, is possible at all.

This work produced celebrated logical puzzles and pushed modal reasoning forward. Diodorus Cronus formulated the Master Argument, concluding that only what is or will be true is possible, and debated the truth conditions of conditional "if-then" statements with Philo the Dialectician. Eubulides of Miletus, a critic of Aristotle, invented several of the paradoxes; Ichthyas helped give them formal statement, as did the early figure Clinomachus of Thurii.

After Eucleides, who also wrote Socratic dialogues, the best-known successor was Stilpo (c. 380–300 BCE), whose work lay chiefly in ethics and who influenced the development of Stoicism. Flourishing through the 4th and 3rd centuries BCE, with its teachers active in Athens and other cities as well as Megara, the school shifted steadily from Eucleides's ethical and metaphysical synthesis toward logic, paradox, and eristic — disputation for its own sake — a later phase that earned it the alternative names Dialectical and Eristic school.