Plato's Theaetetus

In Plato's Theaetetus Plato attempts to show what knowledge is. Socrates asks Theaetetus what he thinks knowledge is. Since Theaetetus answers incorrectly, Socrates presents other definitions about knowledge. One theory is "Man is the Measure of all things." Although this theory comes from Socrates, he still believes it is in need of more explanation. Socrates reverts to Protagoras' teachings and explains his theory on the idea that "Man in the Measure of all things" Socrates presents Protagoras' revised version of the theory that "Man is the Measure of all things" Protagoras' theory states that each man is the measure of truth. According to this, nobody is superior to anyone else and we all are equal in truth. However, some men are wiser because their opinions are more beneficial than those of others. The wise hold beliefs that are beneficial and try to convince others that it's beneficial. For example, professors use their ability to teach others and persuade them to see as they see or at least to challenge their teachings. Protagoras explains, through the use of words, he has the ability to change people's appearance. Protagoras concludes that "Man is the Measure of all things" is true. Protagoras' revised theory is much stronger than the old theory. In the old theory, Socrates explains that man determines what is truth and false. What appears to someone is what it is to him, and what appears to someone else is what it is for that person. Socrates says this is identical to the idea that knowledge is perception. Since perceiving is identical to appearing, then whatever one sees, feels or smells is true. If that is correct, then man is always right and truth changes as man's perception changes. After many objections of this old theory, Socrates concludes that knowledge is not perception. Man cannot be the measure of all things because everyone perceives things differently and things are not always the way they seem. The old theory was simply refuted because