253–254
Theaetetus
Theaet. Certainly he needs science, and perhaps even the greatest of sciences.
Stranger
Str. Then, Theaetetus, what name shall we give to this science? Or, by Zeus, have we unwittingly stumbled upon the science that belongs to free men and perhaps found the philosopher while we were looking for the sophist?
15
Theaetetus
Theaet. What do you mean?
Stranger
Str. Shall we not say that the division of things by classes and the avoidance of the belief that the same class is another, or another the same, belongs to the science of dialectic?
Theaetetus
Theaet. Yes, we shall.
Stranger
Str. Then he who is able to do this has a clear perception of one form or idea extending entirely through many individuals each of which lies apart, and of many forms differing from one another but included in one greater form, and again of one form evolved by the union of many wholes, and of many forms entirely apart and separate. This is the knowledge and ability to distinguish by classes how individual things can or cannot be associated with one another.
Theaetetus
Theaet. Certainly it is.
20
Stranger
Str. But you surely, I suppose, will not grant the art of dialectic to any but the man who pursues philosophy in purity and righteousness.
Theaetetus
Theaet. How could it be granted to anyone else?
Stranger
Str. Then it is in some region like this that we shall always, both now and hereafter, discover the philosopher, if we look for him; he also is hard to see clearly, but the difficulty is not the same in his case and that of the sophist.
Theaetetus
Theaet. How do they differ?
