But the business that we now propose to ourselves, of arguing against the Academicians, appears to some philosophers, and those, too, men of no ordinary calibre, to be a thing that ought not to be done at all; and they think that there is no sense at all in, and no method of disputing with men who approve of nothing; and they blame Antipater, the Stoic, who was very fond of doing so, and say that there is no need of laying down exact definitions of what knowledge is, or perception, or, if we want to render word for word, comprehension, which they call κατάληψις; and they say that those who wish to persuade men that there is anything which can be comprehended and perceived, are acting ignorantly; because there is nothing clearer than ἐνάργεια, as the Greeks call it, and which we may call perspicuity, or evidentness if you like,—coining words, if you will permit us to do so, that this fellow (meaning me) may not think that he is the only person to whom such liberties are permitted. Still they thought that no discourse could be found which should be more intelligible than evidentness itself; and they thought that there was no need of defining things which were so clear. But others declared that they would never be the first to speak in behalf of this evidentness; but they thought that a reply ought to be made to those arguments which were advanced against it, to prevent any one being deceived by them. There are also many men who do not disapprove of the definitions of the evident things themselves, and who think the subject one worthy of being inquired into, and the men worthy of being argued with.