Str. If we assert that the greater has no relation to anything except the less, it will never have any relation to the standard of the mean, will it?
Y. Soc. No.
Str. Will not this doctrine destroy the arts and their works one and all, and do away also with statesmanship, which we are now trying to define, and with weaving, which we did define? For all these are doubtless careful about excess and deficiency in relation to the standard of the mean; they regard them not as non-existent, but as real difficulties in actual practice, and it is in this way, when they preserve the standard of the mean, that all their works are good and beautiful.
Y. Soc. Certainly.
Str. And if we do away with the art of statesmanship, our subsequent search for the kingly art will be hopeless, will it not?
Y. Soc. Certainly.
Str. Then just as in the case of the sophist Footnote 1Plat. Soph. 235 we forced the conclusion that not-being exists, since that was the point at which we had lost our hold of the argument, so now we must force this second conclusion, that the greater and the less are to be measured in relation, not only to one another, but also to the establishment of the standard of the mean, must we not? For if this is not admitted, neither the statesman nor any other man who has knowledge of practical affairs can be said without any doubt to exist.
Y. Soc. Then we must by all means do now the same that we did then.
Str. This, Socrates, is a still greater task than that was; and yet we remember how long that took us; but it is perfectly fair to make about them some such assumption as this.
Y. Soc. As what?
Str. That sometime we shall need this principle of the mean for the demonstration of absolute precise truth. But our belief that the demonstration is for our present purpose good and sufficient is, in my opinion, magnificently supported by this argument—that we must believe that all the arts alike exist and that the greater and the less are measured in relation not only to one another but also to the establishment of the standard of the mean. For if this exists, they exist also, and if they exist, it exists also, but neither can ever exist if the other does not.
Y. Soc. That is quite right. But what comes next?
Str. We should evidently divide the science of measurement into two parts in accordance with what has been said. One part comprises all the arts which measure number, length, depth, breadth, and thickness in relation to their opposites; the other comprises those which measure them in relation to the moderate, the fitting, the opportune, the needful, and all the other standards that are situated in the mean between the extremes.
Y. Soc. Both of your divisions are extensive, and there is a great difference between them.