Protagoras: Fragments & Testimonia

Fragmenta

de Natura Deorum

Lucullus

Adversus Mathematicos

Homo mensura is the famous thesis of the Sophist Protagoras of Abdera, from the 5th century BCE: 'Of all things the measure is man — of things that are, that they are; of things that are not, that they are not.' It makes truth relative to each perceiver, so the wind really is cold for the one who feels it cold and warm for the one who feels it warm. Plato made refuting this relativism a centerpiece of the Theaetetus, and it endures as the classic ancient statement of subjectivism about truth.

The Sophist Protagoras' relativist thesis that 'of all things the measure is man': what appears true to each person is true for them, denying any objective standard above human judgment.

Man the Measure (Homo Mensura)

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