In as many ways as we can change things which are equivalent to one another, in just so many ways we can change the forms of arguments and enthymemes in argumentation. This is an instance: “If you have borrowed and not repaid, you owe me the money: you have not borrowed and you have not repaid; then you do not owe me the money.” To do this skillfully is suitable to no man more than to the philosopher; for if the enthymeme is all imperfect syllogism. it is plain that he who has been exercised in the perfect syllogism must be equally expert in the imperfect also.

“Why then do we not exercise ourselves and one another in this manner?” Because, I reply, at present, though we are not exercised in these things and not distracted from the study of morality, by me at least, still we make no progress in virtue. What then must we expect if we should add this occupation? and particularly as this would not only be an occupation which would withdraw us from more necessary things, but would also be a cause of self conceit and arrogance, and no small cause. For great is the power of arguing and the faculty of persuasion, and particularly if it should be much exercised, and also receive additional ornament from language: and so universally, every faculty acquired by the uninstructed and weak brings with it the danger of these persons being elated and inflated by it. For............