Why, because I cannot help feeling that you are now saying what is not quite consistent or accordant with what you were saying at first about rhetoric. And I am afraid to point this out to you, lest you should think that I have some animosity against you, and that I speak, not for the sake of discovering the truth, but from jealousy of you.

Now if you are one of my sort, I should like to cross-examine you, but if not I will let you alone. And what is my sort? you will ask. I am one of those who are very willing to be refuted if I say anything which is not true, and very willing to refute any one else who says what is not true, and quite as ready to be refuted as to refute-I for I hold that this is the greater gain of the two, just as the gain is greater of being cured of a very great evil than of curing another.

--Socrates in Gorgias (Paragraph break mine, to make it slightly less of a wall of text. This has shown up before, in a somewhat different form.)