208–209
Socrates
SOC. As an example, if you like, take the sun: I think it is enough for you to be told that it is the brightest of the heavenly bodies that revolve about the earth.
Theaetetus
THEAET. Certainly.
Socrates
SOC. Understand why I say this. It is because, as we were just saying, if you get hold of the distinguishing characteristic by which a given thing differs from the rest, you will, as some say, get hold of the definition or explanation of it; but so long as you cling to some common quality, your explanation will pertain to all those objects to which the common quality belongs.
Theaetetus
THEAET. I understand; and it seems to me that it is quite right to call that kind a rational explanation or definition.
20
Socrates
SOC. Then he who possesses right opinion about anything and adds thereto a comprehension of the difference which distinguishes it from other things will have acquired knowledge of that thing of which he previously had only opinion.
Theaetetus
THEAET. That is what we affirm.
Socrates
SOC. Theaetetus, now that I have come closer to our statement, I do not understand it at all. It is like coming close to a scene-painting. In which perspective is the main thing. While I stood off at a distance, I thought there was something in it.
Theaetetus
THEAET. What do you mean?
Socrates
SOC. I will tell you if I can. Assume that I have right opinion about you; if I add the explanation or definition of you, then I have knowledge of you, otherwise I have merely opinion.
Socrates
SOC. But explanation was, we agreed, the interpretation of your difference.
Theaetetus
THEAET. It was.
