2. LOGIC.—The great problem both of the logical faculty and also of logic both as science and art, consists in this, viz., to form and judge of conclusions, and through conclusions to be able to establish a proof. The conclusions, however, arise from propositions, and the propositions from conceptions. According to this natural point of view, which lies in the very nature of the case, Aristotle has divided the content of the logical and dialectical doctrine contained in the different treatises of the Organon. The first treatise in the Organon is that containing the _categories_, a work which treats of the universal determinations of being, and gives the first attempt at an ontology. Of these categories Aristotle enumerates ten; essence, magnitude, quality, relation, the where, the when, position, habit, action, and passion. The second treatise (_de interpretatione_) investigates speech as the expression of thought, and discusses the doctrine of the parts of speech, propositions and judgments. The third are the analytic books, which show how conclusions may be referred back to their principles and arranged in order of their antecedence. The first Analytic contains in two books the universal doctrine of the Syllogism. Conclusions are according to their content and end either apodictic, which possess a certain and incontrovertible truth, or dialectic, which are directed toward that which may be disputed and is probable, or, finally, sophistic, which are announced deceptively as correct conclusions while they are not. The doctrine of apodictic conclusions and thus of proofs is given in the two books of the second Analytic, that of dialectic, is furnished in the eight books of the Topic, and that of sophistic in the treatise concerning “Sophistical Convictions.”