He begins the Analytica Priora by setting forth his general purpose, and defining his principal terms and phrases. His manner is one of geometrical plainness and strictness. It may perhaps have been common to him with various contemporary geometers, whose works are now lost; but it presents an entire novelty in Grecian philosophy and literature. It departed not merely from the manner of the rhetoricians and the physical philosophers (as far as we know them, not excluding even Demokritus), but also from Sokrates and the Sokratic school. For though Sokrates and Plato were perpetually calling for definitions, and did much to make others feel the want of such, they neither of them evinced aptitude or readiness to supply the want. The new manner of Aristotle is adapted to an undertaking which he himself describes as original, in which he has no predecessors, and is compelled to dig his own foundations. It is essentially didactic and expository, and contrasts strikingly with the mixture of dramatic liveliness and dialectical subtlety which we find in Plato.
The terminology of Aristotle in the Analytica is to a certain extent different from that in the treatise De Interpretatione. The Enunciation (Ἀπόφανις) appears under the new name of Πρότασις, Proposition (in the literal sense) or Premiss; while, instead of Noun and Verb, we have the word Term (Ὅρος), applied alike both to Subject and to Predicate.[3] We pass now from the region of declared truth, into that of inferential or reasoned truth. We find the proposition looked at, not merely as communicating truth in itself, but as generating and helping to guarantee certain ulterior propositions, which communicate something additional or different. The primary purpose of the Analytica is announced to be, to treat of Demonstration and demonstrative Science; but the secondary purpose, running parallel with it and serving as illustrative counterpart, is, to treat also of Dialectic; both of them[4] being applications of the inferential or ratiocinative process, the theory of which Aristotle intends to unfold.
[3] Aristot. Analyt. Prior. I. i. p. 24, b. 16: ὅρον δὲ καλῶ εἰς ὃν διαλύεται ἡ πρότασις, οἷον τό τε κατηγορούμενον καὶ τὸ καθ’ οὗ κατηγορεῖται, &c.
Ὅρος — Terminus — seems to have been a technical word first employed by Aristotle himself to designate subject and predicate as the extremes of a proposition, which latter he conceives as the interval between the termini — διάστημα. (Analyt. Prior. I. xv. p. 35, a. 12. στερητικῶν διαστημάτων, &c. See Alexander, Schol. pp. 145-146.)
In the Topica Aristotle employs ὅρος in a very different sense — λόγος ὁ τὸ τί ἦν εἶναι σημαίνων (Topic. I. v. p. 101, b. 39) — hardly distinguished from ὁρισμός. The Scholia take little notice of this remarkable variation of meaning, as between two treatises of the Organon so intimately connected (pp. 256-257, Br.).
[4] Analyt. Prior. I. i. p. 24, a. 25.
The three treatises — 1, Analytica Priora, 2, Analytica Posteriora, 3, Topica with Sophistici Elenchi — thus belong all to one general scheme; to the theory of the Syllogism, with its distinct applications, first, to demonstrative or didactic science, and, next, to dialectical debate. The scheme is plainly announced at the commencement of the Analytica Priora; which treatise discusses the Syllogism generally, while the Analytica Posteriora deals with Demonstration, and the Topica with Dialectic. The first chapter of the Analytica Priora and the last chapter of the Sophistici Elenchi (closing the Topica), form a preface and a conclusion to the whole. The exposition of the Syllogism, Aristotle distinctly announces, precedes that of Demonstration (and for the same reason also precedes that of Dialectic), because it is more general: every demonstration is a sort of syllogism, but every syllogism is not a demonstration.[5]
[5] Ibid. I. iv. p. 25, b. 30.
As a foundation for the syllogistic theory, propositions are classified according to their quantity (more formally than in the treatise De Interpretatione) into Universal, Particular, and Indefinite or Indeterminate;[6] Aristotle does not recognize the Singular Proposition as a distinct variety. In regard to the Universal Proposition, he introduces a different phraseology according as it is looked at from the side of the Subject, or from that of the Predicate. The Subject is, or is not, in the whole Predicate; the Predicate is affirmed or denied respecting all or every one of the Subject.[7] The minor term of the Syllogism (in the first mode of the first figure) is declared to be in the whole middle term; the major is declared to belong to, or to be predicable of, all and every the middle term. Aristotle says that the two are the same; we ought rather to say that each is the concomitant and correlate of the other, though his phraseology is such as to obscure the correlation.
[6] Ibid. I. i. p. 24, a. 17. The Particular (ἐν μέρει), here for the first time expressly distinguished by Aristotle, is thus defined:— ἐν μέρει δὲ τὸ τινὶ ἢ μὴ τινὶ ἢ μὴ παντὶ ὑπάρχειν.