Abstract

The proof of first thesis of Gorgias is an indirect deductive argument constructed by the multiple use of the _modus tollens_ pattern. Those of its premises which are assumed without proofs are misleadingly similar to some logical or analytical truths. If they actually were such truths, some contradictions would have to appear in the proof. In the times of Gorgias the proof could be regarded as correct; the possibility of showing and clearly describing its defects emerged only after formal logic had been invented. Gorgias could announce his thesis seriously – as a thesis of extreme metaphysical nihilism – without being embarrassed. If the proof is a sophistry, then it is a masterpiece among sophistries, the most outstanding achievement of the sophists in this domain.