Of the use of sophistical arguments, and hypothetical, and the like The handling of sophistical and hypothetical arguments, and of those which derive their conclusions from questioning, and in a word the handling of all such arguments, relates to the duties of life, though the many do not know this truth. For in every matter we inquire how the wise and good man shall discover the proper path and the proper method of dealing with the matter. Let, then, people either say that the grave man will not descend into the contest of question and answer, or that, if he does descend into the contest, he will take no care about not conducting himself rashly or carelessly in questioning and answering. But if they do not allow either the one or the other of these things, they must admit that some inquiry ought to be made into those topics on which particularly questioning and answering are employed. For what is the end proposed in reasoning? To establish true propositions, to remove the false, to withhold assent from those which are not plain. Is it enough then to have learned only this? "It is enough," a man may reply. Is it, then, also enough for a man, who would not make a mistake in the use of coined money, to have heard this precept, that he should receive the genuine drachmae and reject the spurious? "It is not enough." What, then, ought to be added to this precept? What else than the faculty which proves and distinguishes the genuine and the spurious drachmae?
Consequently also in reasoning what has been said is not enough; but is it necessary that a man should acquire the faculty of examining and distinguishing the true and the false, and that which is not plain? "It is necessary." Besides this, what is proposed in reasoning? "That you should accept what follows from that which you have properly granted." Well, is it then enough in this case also to know this? It is not enough; but a man must learn how one thing is a consequence of other things, and when one thing follows from one thing, and when it follows from several collectively.
Consider, then if it be not necessary that this power should also be acquired by him who purposes to conduct himself skillfully in reasoning, the power of demonstrating himself the several things which he has proposed, and the power of understanding the demonstrations of others, including of not being deceived by sophists, as if they were demonstrating. Therefore there has arisen among us the practice and exercise of conclusive arguments and figures, and it has been shown to be necessary.
