Str. Yes, for what many clever persons occasionally say, Socrates, fancying that it is a wise remark, namely, that the science of measurement has to do with everything, is precisely the same as what we have just said. For in a certain way all things which are in the province of art do partake of measurement; but because people are not in the habit of considering things by dividing them into classes, they hastily put these widely different relations Footnote 1i.e. relations to each other and relations to the standard of the mean. into the same category, thinking they are alike; and again they do the opposite of this when they fail to divide other things into parts. What they ought to do is this: when a person at first sees only the unity or common quality of many things, he must not give up until he sees all the differences in them, so far as they exist in classes; and conversely, when all sorts of dissimilarities are seen in a large number of objects he must find it impossible to be discouraged or to stop until has gathered into one circle of similarity all the things which are related to each other and has included them in some sort of class on the basis of their essential nature. No more need be said, then, about this or about deficiency and excess; let us only bear carefully in mind that two kinds of measurement which apply to them have been found, and let us remember what those kinds are.
Y. Soc. We will remember.
Str. Now that we have finished this discussion, let us take up another which concerns the actual objects of our inquiry and the conduct of such discussions in general.
Y. Soc. What is it?
Str. Suppose we were asked the following question about a group of pupils learning their letters: When a pupil is asked of what letters some word or other composed,
is the question asked for the sake of the one particular word before him or rather to make him more learned about all words in the lesson?
Y. Soc. Clearly to make him more learned about them all.
Str. And how about our own investigation of the statesman? Has it been undertaken for the sake of his particular subject or rather to make us better thinkers about all subjects?
Y. Soc. Clearly this also is done with a view to them all.
Str. Of course no man of sense would wish to pursue the discussion of weaving for its own sake; but most people, it seems to me, fail to notice that some things have sensible resemblances which are easily perceived; and it is not at all difficult to show them when anyone wishes, in response to a request for an explanation of some one of them, to exhibit them easily without trouble and really without explanation. But, on the other hand, the greatest and noblest conceptions have no image wrought plainly for human vision, which he who wishes to satisfy the mind of the inquirer can apply to some one of his senses and by mere exhibition satisfy the mind.