That the faculties are not safe to the uninstructed
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.