Megarian School

Under Euclid of Megara's successors, particularly Eubulides of Miletus in the fourth century BCE, the Megarian school became known less for a positive doctrine than for a set of logical puzzles that still trouble philosophers of language and logic today. The liar paradox asks what to make of a sentence that says only that it is itself false, since if the sentence is true then it is false, and if it is false then it is true, an apparent contradiction that later logicians would spend over two thousand years trying to resolve without success that satisfies everyone. The sorites, or heap, paradox asks how many grains of sand can be removed one at a time from a heap before it stops being a heap, since removing a single grain never seems to make the difference, yet a single grain is plainly not a heap, a puzzle about vague language that remains an active area of philosophical logic. The Megarians also debated the nature of possibility itself, with Euclid's successor Diodorus Cronus arguing for a strict position, sometimes called the master argument, that only what actually happens was ever really possible, against which the Stoic philosopher Chrysippus later argued at length. Because so little of the school's own writing survives, most of what is known about these debates comes through later authors, chiefly Sextus Empiricus and Cicero, reporting positions the Megarians themselves left in only fragmentary and often disputed form.

Not every Megarian made puzzles the center of the school's work. Stilpo, who led the school in the late fourth and early third centuries BCE, turned it instead toward an ethical teaching close in spirit to Cynicism, arguing that the wise person achieves apatheia, freedom from disturbance, by recognizing that nothing external, wealth, reputation, even a besieged city, is truly one's own to lose. When Demetrius Poliorcetes sacked Megara and offered to spare Stilpo's property, Stilpo is reported to have answered that he had lost nothing, since he carried everything that was really his, his learning and his virtue, within himself, an anecdote later writers repeated as the cleanest statement of the position.

The teaching mattered less for what it said than for who heard it. Among Stilpo's students in Athens was a young Cypriot merchant named Zeno of Citium, who studied with him before founding his own school in the Painted Stoa, and Stoic ethics preserves recognizably Megarian fingerprints in its account of what is and is not within a person's control and in its own use of apatheia as a term of art. The logical puzzles for which the Megarians are chiefly remembered and Stilpo's ethical teaching for a time ran through the same school, and it is the ethical strand, transmitted through Zeno, that reached the widest later audience, carried forward inside Stoicism long after the Megarian school itself had no members left to defend the liar paradox.