Therefore the headings, or “topics,” of rhetoric are not peculiar to a particular field of investigation, but general or “common topics” such as justice or expediency, which express common human relations. To deviate from these into the method peculiar to a given subject-matter, physics for example, is to pass[12] from rhetorical method for presentation over to scientific method for analysis; and this, of course, the speaker must do to the extent of mastering his subject-matter before he presents it. Though he must not forget that his ultimate task is to present to an audience and therefore concretely, neither can he forget that what is to be presented must be acquired. In so far as he investigates he will follow scientific method, the analysis proper to the field, the “special topics.” Thus for his education he needs some study of the “special topics” of those sciences that furnish most of his subject-matter, the “special topics” of ethics and politics. Of these he must have, as part of his equipment, a practical or working knowledge, the orator’s equipment for considering each case within its own field as well as in its general relations to human nature. Aristotle’s distinction here between general and special “topics” coincides with his earlier division (page 10) of the means of persuasion into intrinsic and extrinsic. The extrinsic means are knowledge, to be got by the methods of getting; the intrinsic means are utterance, to be given by the methods of giving. At this point, the opening of Chapter iii,[13] Aristotle makes his scientific division of rhetoric by its fields. The three fields of rhetoric are: (1) the _deliberative_, persuasion in public assemblies as to matters of current discussion, looking to the future, urging expediency: (2) the _forensic_, accusation and defense in courts, looking to the past, urging justice; and (3) the _occasional_,[14] praise or blame, looking to the present, urging honor. The underlying, general, or “final topics” of rhetoric, as distinct from the special topics that it uses from other studies, are thus seen to be expediency (including practicability), justice, honor, and their opposites; and the special topics drawn by rhetoric from philosophy, ethics, and politics may be grouped in a speaker’s compend of these studies according as they apply to the deliberative, the forensic, or the occasional field.