It is obvious, therefore, that a system arranged according to the rules of art is only concerned with proofs; that proof is a sort of demonstration, Exact scientific proof ( ἀπόδειξις ), which probable proof ( πίστις ) only to a certain extent resembles. since we are most strongly convinced when we suppose anything to have been demonstrated; that rhetorical demonstration is an enthymeme, which, generally speaking, is the strongest of rhetorical proofs and lastly, that the enthymeme is a kind of syllogism. Now, as it is the function of Dialectic as a whole, or of one of its parts, Dialectic here apparently includes logic generally, the part being either the Analytica Priori , which deals with the syllogism, or the Sophistici Elenchi , on Fallacies. to consider every kind of syllogism in a similar manner, it is clear that he who is most capable of examining the matter and forms of a syllogism will be in the highest degree a master of rhetorical argument, if to this he adds a knowledge of the subjects with which enthymemes deal and the differences between them and logical syllogisms. For, in fact, the true and that which resembles it come under the purview of the same faculty, and at the same time men have a sufficient natural capacity for the truth and indeed in most cases attain to it; wherefore one who divines well in regard to the truth will also be able to divine well in regard to probabilities. ἔνδοξα , resting on opinion ; defined in the Topics (1.1) as things generally admitted by all, or by most men, or by the wise, and by all or most of these, or by the most notable and esteemed. It is clear, then, that all other rhetoricians bring under the rules of art what is outside the subject, and διότι either = ὅτι , that ; or, (it is clear) why. have rather inclined to the forensic branch of oratory. 
 Nevertheless, Rhetoric is useful, because the true and the just are naturally superior to their opposites, so that, if decisions are improperly made, they must owe their defeat to their own advocates; which is reprehensible. Further, in dealing with certain persons, even if we possessed the most accurate scientific knowledge, we should not find it easy to persuade them by the employment of such knowledge. For scientific discourse is concerned with instruction, Almost equivalent to demonstration or strictly logical proof. but in the case of such persons instruction is impossible; our proofs and arguments must rest on generally accepted principles, as we said in the Topics , 1.2. The Topics is a treatise in eight books on Dialectic and drawing conclusions from probabilities. when speaking of converse with the multitude. Further, the orator should be able to prove opposites, as in logical arguments; not that we should do both (for one ought not to persuade people to do what is wrong), but that the real state of the case may not escape us, and that we ourselves may be able to counteract false arguments, if another makes an unfair use of them. Rhetoric and Dialectic alone of all the arts prove opposites; for both are equally concerned with them. However, it is not the same with the subject matter, but, generally speaking, that which is true and better is naturally always easier to prove and more likely to persuade. Besides, it would be absurd if it were considered disgraceful not to be able to defend oneself with the help of the body, but not disgraceful as far as speech is concerned, whose use is more characteristic of man than that of the body. 
 If it is argued that one who makes an unfair use of such faculty of speech may do a great deal of harm, this objection applies equally to all good things except virtue, and above all to those things which are most useful, such as strength, health, wealth, generalship; for as these, rightly used, may be of the greatest benefit, so, wrongly used, they may do an equal amount of harm. It is thus evident that Rhetoric does not deal with any one definite class of subjects, but, like Dialectic, [is of general application]; also, that it is useful; and further, that its function is not so much to persuade, as to find out in each case the existing means of persuasion. The early sophistical definition was the art of persuasion. The same holds good in respect to all the other arts. For instance, it is not the function of medicine to restore a patient to health, but only to promote this end as far as possible; for even those whose recovery is impossible may be properly treated. It is further evident that it belongs to Rhetoric to discover the real and apparent means of persuasion, just as it belongs to Dialectic to discover the real and apparent syllogism. For what makes the sophist is not the faculty but the moral purpose. But there is a difference: in Rhetoric, one who acts in accordance with sound argument, and one who acts in accordance with moral purpose, are both called rhetoricians; but in Dialectic it is the moral purpose that makes the sophist, the dialectician being one whose arguments rest, not on moral purpose but on the faculty. The essence of sophistry consists in the moral purpose, the deliberate use of fallacious arguments. In Dialectic, the dialectician has the power or faculty of making use of them when he pleases; when he does so deliberately, he is called a sophist. In Rhetoric, this distinction does not exist; he who uses sound arguments as well as he who uses false ones are both known as rhetoricians. Let us now endeavor to treat of the method itself, to see how and by what means we shall be able to attain our objects. And so let us as it were start again, and having defined Rhetoric anew, pass on to the remainder of the subject. Rhetoric then may be defined as the faculty of discovering the possible means of persuasion in reference to any subject whatever. This is the function of no other of the arts, each of which is able to instruct and persuade in its own special subject; thus, medicine deals with health and sickness, geometry with the properties of magnitudes, arithmetic with number, and similarly with all the other arts and sciences. But Rhetoric, so to say, appears to be able to discover the means of persuasion in reference to any given subject. That is why we say that as an art its rules are not applied to any particular definite class of things.