But suppose that the latter should quarrel with us and dispute our statement, can we administer any soothing cordial or advice to him, without revealing to him that there is sad disorder in his wits? We must certainly offer him some good advice, he replied. Come, then, and let us think of something to say to him. Shall we begin by assuring him that he is welcome to any knowledge which he may have, and that we are rejoiced at his having it? But we should like to ask him a question: Does he who has knowledge know something or nothing? (You must answer for him.) I answer that he knows something. Something that is or is not? Something that is; for how can that which is not ever be known? And are we assured, after looking at the matter from many points of view, that absolute being is or may be absolutely known, but that the utterly non-existent is utterly unknown? Nothing can be more certain. Good. But if there be anything which is of such a nature as to be and not to be, that will have a place intermediate between pure being and the absolute negation of being? Yes, between them. And, as knowledge corresponded to being and ignorance of necessity to not-being, for that intermediate between being and not-being there has to be discovered a corresponding intermediate between ignorance and knowledge, if there be such? Certainly. Do we admit the existence of opinion? Undoubtedly. As being the same with knowledge, or another faculty? Another faculty. Then opinion and knowledge have to do with different kinds of matter corresponding to this difference of faculties? Yes. And knowledge is relative to being and knows being. But before I proceed further I will make a division. What division? I will begin by placing faculties in a class by themselves: they are powers in us, and in all other things, by which we do as we do. Sight and hearing, for example, I should call faculties. Have I clearly explained the class which I mean? Yes, I quite understand. Then let me tell you my view about them. I do not see them, and therefore the distinctions of figure, colour, and the like, which enable me to discern the differences of some things, do not apply to them. In speaking of a faculty I think only of its sphere and its result; and that which has the same sphere and the same result I call the same faculty, but that which has another sphere and another result I call different. Would that be your way of speaking? Yes. And will you be so very good as to answer one more question? Would you say that knowledge is a faculty, or in what class would you place it? Certainly knowledge is a faculty, and the mightiest of all faculties. And is opinion also a faculty? Certainly, he said; for opinion is that with which we are able to form an opinion. And yet you were acknowledging a little while ago that knowledge is not the same as opinion? Why, yes, he said: how can any reasonable being ever identify that which is infallible with that which errs?