"SOCRATES: That any kind of mixture that does not in some way or other possess measure of the nature of proportion will necessarily corrupt its ingredients and most of all itself. For there would be no blending in such a case at all but really an unconnected medley, the ruin of whatever happens to be contained in it.
PROTARCHUS: Very true.
SOCRATES: But now we notice that the force of the good has taken up refuge in an alliance with the nature of the beautiful. For measure and proportion manifest themselves in all areas of beauty and virtue.
PROTARCHUS: Undeniably.
SOCRATES: But we said that truth is also inclined along with them in our mixture?
PROTARCHUS: Indeed.
SOCRATES: Well, then, if we cannot capture the good in
one form, we will have to take hold of it in a conjunction of three: beauty, proportion and truth. Let us affirm that these should by right be treated as a unity and be held responsible for what is in the mixture, for goodness is what makes the mixture good in itself."
--Plato,
Philebus