The Path of Knowledge
An authoritative and accessible summary of Plato's Theaetetus   by Robert Cavalier (Carnegie Mellon University).

This article by Carol Poster is an unusually thorough treatment of this important philosopher. From The Internet Encyclopedia of Philosophy.

Protagoras (480-411 B.C.)
A concise and varied account of the philosopher.

Philosophical Background of the
Fifth Century B.C.

An excellent outline of the historical and political context and impact of the sophists.

The Philosophy
of the Sophists
A thoughtful article with related resources from the Radical Academy (which explicity opposes relativism).

An informative article on the Sophists by George Briscoe Kerferd.

A detailed and accessible study of relativism in its various forms by Chris Swoyer (University of Oklahoma) from the Stanford Encyclopedia of Philosophy. It is long, but no longer than it need be to summarize this vital topic.




Plato's Critique

Socrates opposed the Sophists, even though he was accused of being one himself and executed. Plato picked up his mentor's battle against relativism and sophism in general, and Protagoras in particular.  Plato's refutations (given through the voice of Socrates in the dialogues) often involve demonstrating how some main belief of a view leads to contraditions and absurdities.  The following passage provides an example of this sort of refutation as well as presenting one of Socrates' main tenets that developing truth through philosophical discussion is like giving birth.  Socrates likens himself to a midwife who assists in the birthing process.  Thus, rather than giving theories and doctrines of his own, he acts as a facilitator to the intellectual growth of others.  In the following pasage he is asisting young Theaetetus (who is quite enamoured of Pprotagoras) in the labor of giving life to his own ideas about knowledge. 

Theaetetus: Now he who knows perceives what he knows, and, as far as I can see at present, knowledge is perception.
Socrates: Bravely said, boy; that is the way in which you should express your opinion. And now, let us examin together this conception of yours, and see whether it is a true birth or a mere, wind-egg:-You say that knowledge is perception?
Theaetetus: Yes.
Socrates: Well, you have delivered yourself of a very important doctrine about knowledge; it is indeed the opinion of Protagoras, who has another way of expressing it, Man, he says, is the measure of all things, of the existence of things that are, and of the non-existence of things that are not:-You have read him?
Theaetetus: O yes, again and again.
Socrates: Does he not say that things are to you such as they appear to you, and to me such as they appear to me, and that you and I are men?
Theaetetus: Yes, he says so.
Socrates: I am charmed with his doctrine, that what appears is to each one, but I wonder that he did not begin his book on Truth with a declaration that a pig or a dog-faced baboon, or some other yet stranger monster which has sensation, is the measure of all things; then he might have shown a magnificent contempt for our opinion of him by informing us at the outset that while we were reverencing him like a God for his wisdom he was no better than a tadpole, not to speak of his fellow-men-would not this have produced an over-powering effect? For if truth is only sensation, and no man can discern another's feelings better than he, or has any superior right to determine whether his opinion is true or false, but each, as we have several times repeated, is to himself the sole judge, and everything that he judges is true and right, why, my friend, should Protagoras be preferred to the place of wisdom and instruction, and deserve to be well paid, and we poor ignoramuses have to go to him, if each one is the measure of his own wisdom? Must he not be talking ad captandum in all this? I say nothing of the ridiculous predicament in which my own midwifery and the whole art of dialectic is placed; for the attempt to supervise or refute the notions or opinions of others would be a tedious and enormous piece of folly, if to each man his own are right; and this must be the case if Protagoras Truth is the real truth, and the philosopher is not merely amusing himself by giving oracles out of the shrine of his book.

On one level Socrates' argument seems abusive and silly, suggesting that the claim "Of all things the measure is Man" leaves out animals and other sensate beings.  His point is that if knowledge is perception, then anything with any perception (sensation) at all is equally a measure of all things.  It seems that Protagoras might well respond that this is so, baboon reality is relative to their own perception, as it creates no special problem for the relativism.

Yet, Socrates is setting up a serious problem for relativism.  Usually when someone claims to know the truth of a matter, especially a great and general principle, we may challenge them to give proof.  Protagoras is claiming to have a general principle that applies to everyone.  In saying "Of all things the measure is Man, of the things that are, that they are, and of the things that are not, that they are not" Protagoras is not merely reporting how things appear to him or to a certain group of people.  Nor is he referring to some particular experience or phenomena. His book is titled Truth not "Truth for me." Protagoras is making a philosophical statement about the structure of reality.  If it is true, then it is true for all of us, pigs and baboons included. 

Herein lies the problem.  If Protagoras' claim is correct, then what could it mean for such a claim to be true?  In a relativist system, can any general statement be true?  After all, it would be true for some people and not true for others. Moreover, general claims that stand like rules or laws are not based in sensory experience.  Protagoras is presenting an item of knowledge that is not relative to percievers, indeed it reads like an absolute claim in which all things are subject to measure of Man.  It appears that there is a kind of knowledge that is not perception (which is precisely what Plato wants to establish). It is in the realm of philosophical knowledge.

Protagoras makes a claim that seems to be self-defeating.  A reply that seems entirely consistent with relativism may be; "relativism may be true-for-you but it is not true-for-me."  This leaves Protagoras in a curious position as he can only say what is so relative to his own beliefs and perceptions.  That is what Socrates means in saying; "while we were reverencing him like a God for his wisdom he was no better than a tadpole."  That is, Protagoras can lay no claim to having greater wisdom, deeper knowledge, or truer principles that any other sensate creature.  Every individual has their own truth and reality.  What, then, could Protagoras' individual reality have to do with anyone else?  If we take Protagoras' most famous statement to heart, then it seems to defeat any possibility of regarding his claim as a general truth.  Relativism collapses under its own logical inconsistency.

Yet, this criticism depends upon the interpretation of relativism as a theory about individual perceptions alone.  To develop a more sophisticated version of the theory, Plato has Socrates provide a rebuttal that Protagoras might have made (though Protagaoras was dead at the time of the dialogue).

As to your talk about pigs and baboons, you are yourself behaving like a pig, and you teach your hearers to make sport of my writings in the same ignorant manner; but this is not to your credit. For I declare that the truth is as I have written, and that each of us is a measure of existence and of non-existence. Yet one man may be a thousand times better than another in proportion as different things are and appear to him. And I am far from saying that wisdom and the wise man have no existence; but I say that the wise man is he who makes the evils which appear and are to a man, into goods which are and appear to him. And I would beg you not to take my words in the letter, but to take the meaning of them as I will explain them. Remember what has been already said,-that to the sick man his food appears to be and is bitter, and to the man in health the opposite of bitter. Now I cannot conceive that one of these men can be or ought to be made wiser than the other: nor can you assert that the sick man because he has one impression is foolish, and the healthy man because he has another is wise; but the one state requires to be changed into the other, the worse into the better. As in education, a change of state has to be effected, and the sophist accomplishes by words the change which the physician works by the aid of drugs. Not that any one ever made another think truly, who previously thought falsely. For no one can think what is not, or think anything different from that which he feels; and this is always true. But as the inferior habit of mind has thoughts of kindred nature, so I conceive that a good mind causes men to have good thoughts; and these which the inexperienced call true, I maintain to be only better, and not truer than others. And, O my dear Socrates, I do not call wise men tadpoles: far from it; I say that they are the physicians of the human body, and the husbandmen of plants-for the husbandmen also take away the evil and disordered sensations of plants, and infuse into them good and healthy sensations-aye and true ones; and the wise and good rhetoricians make the good instead of the evil to seem just to states; for whatever appears to a state to be just and fair, so long as it is regarded as such, is just and fair to it; but the teacher of wisdom causes the good to take the place of the evil, both in appearance and in reality. And in like manner the Sophist who is able to train his pupils in this spirit is a wise man, and deserves to be well paid by them. And so one man is wiser than another; and no one thinks falsely, and you, whether you will or not, must endure to be a measure. On these foundations the argument stands firm, which you, Socrates, may, if you please, overthrow by an opposite argument, or if you like you may put questions to me-a method to which no intelligent person will object, quite the reverse. But I must beg you to put fair questions: for there is great inconsistency in saying that you have a zeal for virtue, and then always behaving unfairly in argument. The unfairness of which I complain is that you do not distinguish between mere disputation and dialectic: the disputer may trip up his opponent as often as he likes, and make fun; but the dialectician will be in earnest, and only correct his adversary when necessary, telling him the errors into which he has fallen through his own fault, or that of the company which he has previously kept. If you do so, your adversary will lay the blame of his own confusion and perplexity on himself, and not on you; will follow and love you, and will hate himself, and escape from himself into philosophy, in order that he may become different from what he was. But the other mode of arguing, which is practised by the many, will have just the opposite effect upon him; and as he grows older, instead of turning philosopher, he will come to hate philosophy. I would recommend you, therefore, as I said before, not to encourage yourself in this polemical and controversial temper, but to find out, in a friendly and congenial spirit, what we really mean when we say that all things are in motion, and that to every individual and state what appears, is. In this manner you will consider whether knowledge and sensation are the same or different, but you will not argue, as you were just now doing, from the customary use of names and words, which the vulgar pervert in all sorts of ways, causing infinite perplexity to one another. Such, Theodorus, is the very slight help which I am able to offer to your old friend; had he been living, he would have helped himself in a far more gloriose style.




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