<P> Protagoras is credited with the philosophy of relativism, which he discusses in his work, Truth (also known as Refutations). Although knowledge of his work is limited, discussion of Protagoras' relativism is based on one of his most famous statements: "Man is the measure of all things: of the things that are, that they are, of the things that are not, that they are not ." By this, Protagoras meant that each individual is the measure of how things are perceived by that individual . Therefore, things are, or are not, true according to how the individual perceives them . For example, Person X may believe that the weather is cold, whereas Person Y may believe that the weather is hot . According to the philosophy of Protagoras, there is no absolute evaluation of the nature of a temperature because the evaluation will be relative to who is perceiving it . Therefore, to Person X, the weather is cold, whereas to Person Y, the weather is hot . This philosophy implies that there are no absolute "truths". The truth, according to Protagoras, is relative, and differs according to each individual . </P> <P> As with many fragments of the pre-Socratic philosophers, this phrase has been passed down through the ages, without any context, and consequently, its meaning is open to interpretation . His use of the word χρήματα (chrēmata, "things used") instead of the general word ὄντα (onta, "entities") signifies, however, that Protagoras was referring to things that are used by, or in some way, related to, humans, such as properties, social entities, ideas, feelings, judgments, which originate in the human mind . Protagoras did not suggest that humans must be the measure of the motion of the stars, the growing of plants, or the activity of volcanoes . </P> <P> As many modern thinkers will, Plato ascribes relativism to Protagoras and uses his predecessor's teachings as a foil for his own commitment to objective and transcendent realities and values . Plato ascribes to Protagoras an early form of what John Wild categorized as phenomenalism . That being an assertion that something that is, or appears for a single individual, is true or real for that individual . </P> <P> However, as described in Plato's Theaetetus, Protagoras's views allow that some views may result from an ill body or mind . He stressed that although all views may appear equally true, and perhaps, should be equally respected, they certainly are not of equal gravity . One view may be useful and advantageous to the person who has it, while the perception of another may prove harmful . Hence, Protagoras believed that the sophist was there to teach the student how to discriminate between them, i.e., to teach "virtue". </P>

Gorgias claimed man is the measure of all things