Plato's Theaetetus

FIRST SELECTION: KNOWLEDGE IS PERCEPTION AND PERCEPTION IS RELATIVE TO THE PERCEIVER.

Socrates runs into the young Theaetetus with his teacher, Theodorus. Before long, he engages Theaetetus in a conversation on the question, What is knowledge? Theaetetus' first answer is, "Knowledge is perception," i.e. all knowledge is built up from acts of perceptual experience, so that eventually, through memory and experience, sets of perceptual properties are associated with one another under concepts, and related to human fears and desires. This leads Socrates to introduce the Protagorean idea, that perceptual experience is subjective (relative to the individual), and never more than that--human beings may collectively agree to define certain things as objective or absolutely true, but since all knowledge is based on the individual perspective, and that is relative, there is no truly universal, objective knowledge.

Soc. 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 is the measure of all things, of the existence of things that are, and of the non-existence of things that are not, he says--You have read him? --Theaet. O yes, again and again. Soc. 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? --Theaet. Yes, he says so. Soc. A wise man is not likely to talk nonsense. Let us try to understand him: the same wind is blowing, and yet one of us may be cold and the other not, or one may be slightly and the other very cold? --Theaet. Quite true.

Soc. Now is the wind, regarded not in relation to us but absolutely, cold or not; or are we to say, with Protagoras, that the wind is cold to him who is cold, and not to him who is not? --Theaet. I suppose the last. Soc. Then it must appear so to each of them? --Theaet. Yes. Soc. And "appears to him" means the same as "he perceives." --Theaet. True. Soc. Then appearing and perceiving coincide in the case of hot and cold, and in similar instances; for things appear, or may be supposed to be, to each one such as he perceives them? --Theaet. Yes. Soc. Then perception is always of existence, and being the same as knowledge is unerring? Theaet. Clearly. Soc. The object, when it becomes sweet or sour and so on, must become so to someone; it cannot become sweet and yet sweet to nobody. --Theaet. Correct.

Soc. Thus in general, nothing remains . . . but that it [the perceived object[ and I [the perceiving subject] should be or become . . . for each other; necessity binds together our existence; but binds neither of us to anything else, nor each of us to himself; so we can only be bound to one another. --Theaet. That is true. Soc. Accordingly, whether we speak of something ‘being’ or of its ‘becoming,’ we must speak of it as being or becoming for someone, or of something or toward something; but we must not speak . . . of a thing as either being or becoming anything just in and by itself. --Theaet. So it seems. Soc. And it is out of perception and memory that our ideas of things and their properties, and indeed all of our opinions and beliefs arise? --Theaet. Yes, that must be true also.

Soc. So that all knowledge, as you say, comes down to perception, and since perception is relative to the individual perceiver, there is no 'objective' or 'absolute' knowledge of things, but at best we can have agreement among different perceivers, as to what we call 'objectively real'? Theaet. Yes, that follows also. For whatever appears to be true to one person, is true for him, though of course it may not be true to another person or to the people in his community, what they agree to be true...

SECOND SELECTION: WISDOM IS KNOWING HOW TO PERSUADE PEOPLE OF THE MORE USEFUL OPINION

Socrates has attacked Protagoras' saying, claiming that Protagoras' views imply that madmen and baboons and tadpoles are no more foolish than the greatest Sophists, since truth is entirely relative in his opinion. Protagoras insists there is a critical difference between the wise and the foolish--the 'wise man' (Sophist) in whatever field knows how to persuade people of what is more useful and good. But all 'truth' is relative.

Protag: Each of us is an equally true measure of existence and non-existence. Yet one man may be better than another in proportion as different things are and appear to him. .   . .  I do not say that wisdom and the wise man do not exist; I merely say that the wise man is he who makes the bad things which appear and are to a man, into good things which are and appear to him.
        Do you see my meaning: to the sick man his food appears to be and is bitter, and to the healthy man the opposite. Now I do not  say that the sick man, because he has one impression, is mistaken, and the healthy man is correct; I say that the one condition should be changed into the other--the worse into the better. It is the same in education: a change of condition should be brought about, the Sophist doing with words what doctors do with drugs. Not that the one is made to think truly, who had thought falsely--for no one can think what is not, or think anything different from what he feels. But just as an inferior habit of mind has inferior thoughts, so a good mind makes men have good thoughts; and inexperienced people call true, I maintain to be only better--not truer than others. . . .
        And 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 even gardeners take away the bad and disordered sensations of plants, and infuse into them good and healthy sensations--i.e. ‘true’ ones. Similarly, wise and good rhetoricians make what is beneficial, rather than what is harmful, seem ‘just’ to city-states; for whatever appears to a city-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 makes the good [benefitical] take the place of the bad [harmful, evil], both in appearance and in reality. And this is the wisdom of the Sophist.

THIRD SELECTION. THE COURT-ROOM AS A MODEL OF THE PROCESS OF KNOWLEDGE.

Socrates challenges Protagoras idea that there is nothing more than "opinion," ultimately formed by or based on individual perceptions, all of which is relative to the individual, or the group which shares the same beliefs. He then explains that Protagoras would defend the idea that the court-room can function as a model of knowledge. 'Knowledge', he would say, is the 'winning opinion,' and the wise man is the one who knows how to persuade others what to think.

Soc. The profession of the great wise ones who are called orators and lawyers persuade men by their art and make them think whatever they like, but they do not 'teach' them. Do you imagine that there are any teachers in the world so clever as to be able to convince others of the truth about acts of robbery or violence, of which they were not eyewitnesses?
Theaet. Certainly not, they can only persuade them.
Soc. And would you not say that persuading them is making them have an opinion?
Theaet. To be sure.
Soc. When, therefore, the judges and jury are justly persuaded about matters which you can know only by seeing them, and not in any other way, and when judging of them from an eye-witness report they attain a true opinion about them, they judge without knowledge and yet are rightly persuaded, if they have judged well.
Theaet. Certainly.
Soc. And yet, O my friend, if true opinion in law courts and knowledge were the same, the perfect judge could not have judged rightly without knowledge; and therefore I must infer that they are not the same. And yet...do you know what Protagoras would say to all this?
Theaet. What?
Soc. He would surely say that there is no difference between a law-court and knowledge, for the law-court establishes what is true for all, just as when men agree about what they see or think is right, that establishes what is true and what is false, what is just and what is unjust, what is noble and what is base.
Theaet. What happens then to the idea of wisdom?
Soc. That is where is his Sophist comes in again. The Sophist is the one who can convince the court of what to believe. Of course, he must start out with all the different beliefs they have already, which are like the laws they all agree on. But he can convince them which witnesses to believe, and which to reject. And if he is really wise, he can even convince them, right in the courtroom, to change those laws.
Theaet. You mean he would reject your idea, that judges should base their verdicts on knowledge, rather than mere opinion?
Soc. Absolutely. He would say this distinction does not really exist. All there is -- is opinion, which is "justified" differently to different people. The true Sophist will find the way to 'prove' what he says is true, i.e. will find a way to convince people, using whatever witnesses or other means he needs.