oras tried to explain the ideas of the human mind "psycho-genetically." Protagoras declared that the entire psychical life of the human being was such that it consisted only in perceptions. This was a form of sensualism, and Protagoras believed that the world could only be perceived through the senses. This was related to ideas of motion, and it was on motion that perception rested, as does every process by which things come to be or occur in the world. This idea was accepted by most of the philoso
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