Part 121

§ 76-87.

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To return, then, to the original subject. Those who maintain that whatever appears to each person exists to him to whom it appears, persist that what a city enacts as appearing just to itself is just to that city as long as it continues in force; but in enacting laws the real object is to make them as advantageous to itself as possible, but what is advantageous regards also the future, for laws are enacted that they may be advantageous for the future. But if man is the measure of all things, he must also contain within himself the criterion of things about to happen; yet it will be admitted, in a variety of instances that are adduced, that a person who is skilled is better able to judge of the future than one who is unskilled: and Protagoras himself can judge beforehand better than any private person what arguments are likely to be available in a court of justice, so that not every man, but the wise man only, is the true measure of things.

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Footnote 139:

§ 87-91.

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This part of the argument being brought to a close, Socrates next proposes to consider the essence that is said to consist in motion, a doctrine which the followers of Heraclitus were then advocating very strenuously. Now there are two species of motion, removal and change; the former is when a thing passes from one place to another, the latter a change of quality, as when a thing becomes black from white, or hard from soft; and all things must undergo both kinds of motion, otherwise the same thing would be both in motion and at rest at the same time, and in that case it would not be more correct to say that all things are in motion than that they are at rest. Since then every thing must be continually undergoing a process of change at the same time that it is in motion, there can be nothing fixed and certain, so that perception cannot be science, for, as all things are in motion; perception itself, which results from the relation between the object and the percipient, must be in a constant state of motion and change.

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Footnote 140:

§ 91-100.

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Theætetus now resumes the argument, and though it would seem that Protagoras’s doctrine had been already sufficiently refuted, yet Socrates resolves to try it by one more test. Each sense has its peculiar perception, and such things as are perceived by one faculty cannot be perceived by another; for instance, what is perceived by hearing cannot be perceived by sight, and what is perceived by sight cannot be perceived by hearing; yet we can form a notion of them both together, and observe what properties they have in common, and how they differ: this, however, is not done by the senses, but by the soul itself, for children as soon as they are born are able to perceive by the bodily organs, but only arrive, with much labour and difficulty, at the power of comparing things with each other, and so obtain a knowledge of them, whence again it follows that perception and science are not the same.

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Footnote 141:

§ 101-107.

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The first definition of science attempted by Theætetus being thus overthrown, Socrates again asks him, What science is. To which he answers that it appears to be true judgment. Socrates however thinks proper first to enquire whether there is such a thing as false judgment. People, he says, must either know or not know things about which they form judgments. Now false judgments are formed, when a person thinks that things which he does not know are certain other things that he does not know, or when he thinks that things which he does know are other things that he does know, or that things which he does not know are things that he does know. But none of these things can happen, therefore it is not possible to form false judgments. Again if existence is put for knowledge a similar train of reasoning leads to the same conclusion. A third method of forming false judgments may be when any one says that any real object is another real object, changing one for the other in his thoughts. But in that case he must think of both of them or one only; if the former he would contradict himself; if the latter he cannot judge that the one is the other, for he thinks of one only, so that neither in this way can false judgment be formed. There still remains another mode in which false judgments may be formed. Suppose that we have in our souls a waxen tablet of various qualities in different persons: on this tablet are impressed the images of our perceptions and thoughts, and whatever is so impressed we remember and know so long as the image remains. But by examining every possible mode by which perception in the senses and impressions in the mind can be varied and inter-changed, it will be found that false judgment takes place where either the perception or the impression is imperfect and indistinct.

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Footnote 142:

§ 108-125.

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Socrates, however, is not satisfied with this conclusion, that false judgment proceeds from the conjunction of perception with thought, and shews that the mind alone by itself may err, for instance a man may think that seven and five make eleven, though he knows they make twelve; so that there must be either no false judgment at all, or it is possible for a person not to know what he knows. Theætetus is unable to choose between these alternatives. Socrates therefore proposes to abandon their present course of argument and at once to enquire what it is to know. Some people say it is to have science, Socrates prefers saying it is to possess science; for having differs from possessing in that what we have, we use, but what we possess, we use or not as we please. Suppose the soul then to be a kind of aviary containing all sorts of birds, and let the birds stand for sciences; now all the sciences that are shut up in this aviary a man may be said to possess, but when he has occasion to use any particular science, he may by mistake take one instead of another, thus when he thinks that eleven is twelve he takes the science of eleven instead of that of twelve, and so judges falsely; but when he takes that which he endeavours to take, he judges truly. Still another even worse inconvenience appears to Socrates to follow from this; for it is absurd to suppose that a person who has the science of any thing should at the same time be ignorant of that thing; and if that can be, nothing hinders but that ignorance when present should make us know something. So that after all they have only come round again to the point from whence they started and have still to enquire what science is. Theætetus persists in answering that it is true judgment. But Socrates shews that this cannot be the case; for that judges, who listen to the arguments of lawyers, form true judgments without science, whence it follows that true judgment and science are not the same.

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Footnote 143:

§ 126-138.

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Theætetus, pressed by this objection, attempts a third definition of science, and says it is true judgment in conjunction with reason. But then, observes Socrates, how are we to distinguish the things that can be known from those that cannot? For instance, elements cannot be defined, but things composed of them can be defined. Again, elements can be perceived but not known, for he who cannot give an explanation of a thing cannot know it, but things compounded of them, because they can be defined, can also be known. Theætetus agrees to this; but Socrates is not satisfied with the statement, that the elements are unknown, but the nature of things compounded of them known. He illustrates his objection by an examination of the component parts of a syllable, and shews that if a whole is known its parts must also be known; if, then, letters are the elements of a syllable, being also the parts of it, they must also be known as well as the syllable.