YOUNG SOCRATES: I will try;—there appears to me to be one management of men and another of beasts.- Plato, "Statesman"
STRANGER: You have certainly divided them in a most straightforward and manly style; but you have fallen into an error which hereafter I think that we had better avoid.
YOUNG SOCRATES: What is the error?
STRANGER: I think that we had better not cut off a single small portion which is not a species, from many larger portions; the part should be a species. To separate off at once the subject of investigation, is a most excellent plan, if only the separation be rightly made; and you were under the impression that you were right, because you saw that you would come to man; and this led you to hasten the steps. But you should not chip off too small a piece, my friend; the safer way is to cut through the middle; which is also the more likely way of finding classes. Attention to this principle makes all the difference in a process of enquiry.
YOUNG SOCRATES: What do you mean, Stranger?
STRANGER: I will endeavour to speak more plainly out of love to your good parts, Socrates; and, although I cannot at present entirely explain myself, I will try, as we proceed, to make my meaning a little clearer.
YOUNG SOCRATES: What was the error of which, as you say, we were guilty in our recent division?
STRANGER: The error was just as if some one who wanted to divide the human race, were to divide them after the fashion which prevails in this part of the world; here they cut off the Hellenes as one species, and all the other species of mankind, which are innumerable, and have no ties or common language, they include under the single name of 'barbarians,' and because they have one name they are supposed to be of one species also. Or suppose that in dividing numbers you were to cut off ten thousand from all the rest, and make of it one species, comprehending the rest under another separate name, you might say that here too was a single class, because you had given it a single name. Whereas you would make a much better and more e-qual and logical classification of numbers, if you divided them into odd and even; or of the human species, if you divided them into male and female; and only separated off Lydians or Phrygians, or any other tribe, and arrayed them against the rest of the world, when you could no longer make a division into parts which were also classes.
YOUNG SOCRATES: Very true; but I wish that this distinction between a part and a class could still be made somewhat plainer.
STRANGER: O Socrates, best of men, you are imposing upon me a very difficult task. We have already digressed further from our original intention than we ought, and you would have us wander still further away. But we must now return to our subject; and hereafter, when there is a leisure hour, we will follow up the other track; at the same time, I wish you to guard against imagining that you ever heard me declare—
YOUNG SOCRATES: What?
STRANGER: That a class and a part are distinct.
YOUNG SOCRATES: What did I hear, then?
STRANGER: That a class is necessarily a part, but there is no similar necessity that a part should be a class; that is the view which I should always wish you to attribute to me, Socrates.
YOUNG SOCRATES: So be it.