It will be seen clearly from the foregoing remarks that there is a great difference between one thesis and another as to facility of attack or defence in Dialectic. If the thesis be an Universal Affirmative proposition, it can be demonstrated only in the First figure, and only by one combination of premisses; while, on the other hand, it can be impugned either by an universal negative, which can be demonstrated both in the First and Second figures, or by a particular negative, which can be demonstrated in all the three figures. Hence an Universal Affirmative thesis is at once the hardest to defend and the easiest to oppugn: more so than either a Particular Affirmative, which can be proved both in the First and Third figures; or a Universal Negative, which can be proved either in First or Second.[46] To the opponent, an universal thesis affords an easier victory than a particular thesis; in fact, speaking generally, his task is easier than that of the defendant. [Footnote 46: Analyt. Prior. I. xxvi. p. 42, b. 27, p. 43, a. 15.] In the Analytica Priora, Aristotle proceeds to tell us that he contemplates not only theory, but also practice and art. The reader must be taught, not merely to understand the principles of Syllogism, but likewise where he can find the matter for constructing syllogisms readily, and how he can obtain the principles of demonstration pertinent to each thesis propounded.[47] [Footnote 47: Ibid. I. xxvii. p. 43, a. 20: [Greek: pô=s d' eu)porê/somen au)toi\ pro\s to\ tithe/menon a)ei\ sullogismô=n, kai\ dia\ poi/as o(dou= lêpso/metha ta\s peri\ e(/kaston a)rcha/s, nu=n ê)/dê lekte/on; ou) ga\r mo/non i)/sôs dei= tê\n ge/nesin theôrei=n tô=n sullogismô=n, a)lla\ kai\ tê\n du/namin e)/chein tou= poiei=n.] The second section of Book I. here begins.] A thesis being propounded in appropriate terms, with subject and predicate, how are you the propounder to seek out arguments for its defence? In the first place, Aristotle reverts to the distinction already laid down at the beginning of the Categoriæ.[48] Individual things or persons are subjects only, never appearing as predicates--this is the lowest extremity of the logical scale: at the opposite extremity of the scale, there are the highest generalities, predicates only, and not subjects of any predication, though sometimes supposed to be such, as matters of dialectic discussion.[49] Between the lowest and highest we have intermediate or graduate generalities, appearing sometimes as subjects, sometimes as predicates; and it is among these that the materials both of problems for debate, and of premisses for proof, are usually found.[50] [Footnote 48: Ibid. I. xxvii. p. 43, a. 25, seq.]