Megarian School

The claim

The good is one thing under many names. And whatever is possible either is or will be actual — nothing is possible that never happens.

What it held

Euclides of Megara heard Socrates and took from him the unity of virtue; he took from Parmenides the conviction that being is one. Combining them gives the school's ethical claim, that the good is a single thing called by different names, and its method, which is pure dialectic.

What the Megarians are remembered for, though, are the puzzles. The Liar — a man says he is lying, and is he? The Sorites — remove one grain from a heap and it is still a heap, so when does it stop being one? The Veiled Man — you know your brother, you do not know the veiled man, the veiled man is your brother. The Horns — what you have not lost you still have, you have not lost horns.

These are not jokes. Each targets a real weakness: self-reference, vagueness, and the opacity of belief contexts. They were not satisfactorily answered in antiquity and the Sorites is still an open problem.

Diodorus Cronus went further with the Master Argument, showing that three plausible claims about possibility, time and truth cannot all be held together. His answer was that only what actually happens was ever possible.

How it argued

Refutation by paradox rather than by construction. Argue an opponent into a position that cannot be held, and offer nothing positive in its place.

What it was arguing against

Anyone whose account of possibility, identity or predication turns out to break under pressure — which in practice meant the Peripatetics and later the Stoics.

Where it disagreed with itself

Whether Diodorus' determinism follows or whether one of the three premises can be dropped, which is where Chrysippus went to work and where modal logic starts.

Common misconceptions

That the paradoxes were sophistical games. Aristotle and the Stoics both took them seriously enough to write against them, and the Sorites remains a live problem in the philosophy of language.

How it began

Euclides of Megara was among those present at Socrates' death, and is said to have walked twenty miles into Athens by night, disguised, when Megarians were banned from the city, in order to keep hearing him.

What became of it

Absorbed into Stoic logic, which took the modal problems and the conditional and did the work the Megarians started. Nothing of theirs survives directly.

Lasting influence

Stoic propositional logic descends from it, and through that, all of it. The debate over the truth conditions of conditionals begins with Diodorus and Philo and has not ended.

Why it still matters

The Sorites is the standard problem of vagueness. The Master Argument is where the philosophy of time and modality meet, and both are active fields.

Put another way

A heap of sand with one grain being taken away, and a demand to say exactly when it stopped being a heap.

Where to start

Diogenes Laertius, then any modern treatment of the Sorites — the problem is more alive now than the school ever was.

The surprising bit

Diodorus is said to have died of shame after failing to solve a puzzle put to him at dinner by Stilpo, in front of a king.

In their own words

Connections

Answers

Eleatic School

Influenced

Early Stoicism

The verdict

A school remembered for its jokes, which turn out to be four of the hardest problems in logic.

Sources

• Stanford Encyclopedia of Philosophy