Protagoras

Protagoras was a fifth-century BCE Greek sophist and philosopher, best known for the claim that “man is the measure of all things,” associated with relativism and human judgment.

Man Is the Measure: A surviving fragment attributed to Protagoras says that the human being is the measure of all things. This formulation is the central surviving statement associated with Protagoras.
Fifth-century Athens: The Greek city-state of Athens during the fifth century BCE, a period of political and cultural expansion. Its democratic institutions and public life created demand for persuasive civic education.
Socrates: An Athenian philosopher who questioned interlocutors about virtue, knowledge, and the good life. Platonic dialogues place Socrates in direct debate with Protagoras over whether virtue can be taught.
Rhetoric: The art of effective speaking or writing, especially in public argument and persuasion. Protagoras taught skills that helped students argue and participate in civic life.
Plato's Protagoras: A Platonic dialogue in which Socrates debates Protagoras about virtue, education, and political competence. It is the fullest surviving literary encounter with Protagoras as a character and teacher.
Relativism: The view that truth, knowledge, or value depends in some way on a standpoint or framework. Protagoras’s measure doctrine is a classic source for debates about whether truth varies by person.
Sophistic Movement: A diverse group of itinerant Greek teachers who taught rhetoric and other skills for public life, especially in the fifth century BCE. Protagoras became one of the movement’s best-known teachers and intellectuals.
Gorgias: A fifth-century BCE Greek sophist renowned for rhetorical skill and philosophical arguments about language and reality. He was a prominent contemporary whose work shows the range of sophistic thought beyond Protagoras.
Athenian Democracy: The political system in which eligible male citizens of Athens participated directly in public decisions. Its courts and assemblies made persuasive speech a practical source of influence.
Plato's Theaetetus: A Platonic dialogue investigating knowledge through proposals including perception and true judgment. It examines a Protagorean account of perception and tests its consequences for knowledge.

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