Protagoras (490 BC – 420 BC)

Protagoras is an agnostic: “Many things prevent knowledge including the obscurity of the subject and the brevity of human life.” Protagoras’ epistemology reminds of a type of phenomenalism according to which reality as people understand it is determined by their subjectivity. Able to make the worse line of reasoning appear superior, the sophist insists that one has to always strengthen the weakest argument because the less appealing argument can hide the best answer. Interpreted as a form of radical relativism, Protagoras’ idea that “man is the measure of all things” shows that his philosophical preoccupations are part of a shift in the ancient Greek philosophical focus from natural philosophy to human philosophy.