Plutarch's Platonic questions (1.2)

Now, however useful a thing judgment is, it is mightily impeached by the begetting of a man’s own fancies. For the lover is blinded with the thing loved; and nothing of a man’s own is so beloved as is the opinion and discourse which he has begotten. And the distribution of children, said to be the justest, in respect of discourses is the unjustest; for there a man must take his own, but here a man must choose the best, though it be another man’s. Therefore he that has children of his own, is a worse judge of other men’s; it being true, as the sophister said well, The Eleans would be the most proper judges of the Olympic games, were no Eleans gamesters. So he that would judge of disputations cannot be just, if he either seeks the bays for himself, or is himself antagonist to either of the antagonists. For as the Grecian captains, when they were to decide by their suffrages who had behaved himself the best, every man of them voted for himself; so there is not a philosopher of them all but would do the like, besides those that acknowledge, like Socrates, that they can say nothing that is their own; and these only are the pure uncorrupt judges of the truth. For as the air in the ears, unless it be still and void of noise in itself, with out any sound or buzzing, does not exactly take sounds; so the philosophical judgment in disputations, if it be disturbed and obstreperous within, is hardly comprehensive of what is said without. For our familiar and inbred

opinion will not admit that which is at variance with itself, as the number of sects and parties proves, of which philosophy—if she deals with them in the best manner—must hold one to be right, and all the others to be at war with the truth in their opinions.