This method of procedure is alike applicable to demonstration in Philosophy or in any of the special sciences,[63] and to debate in Dialectic. In both, the premisses or principia of syllogisms must be put together in the same manner, in order to make the syllogism valid. In both, too, the range of topics falling under examination is large and varied; each topic will have its own separate premisses or principia, which must be searched out and selected in the way above described. Experience alone can furnish these principia, in each separate branch or department. Astronomical experience — the observed facts and phenomena of astronomy — have furnished the data for the scientific and demonstrative treatment of astronomy. The like with every other branch of science or art.[64] When the facts in each branch are brought together, it will be the province of the logician or analytical philosopher to set out the demonstrations in a manner clear and fit for use. For if nothing in the way of true matter of fact has been omitted from our observation, we shall be able to discover and unfold the demonstration, on every point where demonstration is possible; and, wherever it is not possible, to make the impossibility manifest.[65]
[63] Ibid. p. 46, a. 8: κατὰ μὲν ἀλήθειαν ἐκ τῶν κατ’ ἀλήθειαν διαγεγραμμένων ὑπάρχειν, εἰς δὲ τοὺς διαλεκτικοὺς συλλογισμοὺς ἐκ τῶν κατὰ δόξαν προτάσεων.
Julius Pacius (p. 257) remarks upon the word διαγεγραμμένων as indicating that Aristotle, while alluding to special sciences distinguishable from philosophy on one side, and from dialectic on the other, had in view geometrical demonstrations.
[64] Analyt. Prior. I. xxx. p. 46, a. 10-20: αἱ δ’ ἀρχαὶ τῶν συλλογισμῶν καθόλου μὲν εἴρηνται — ἴδιαι δὲ καθ’ ἑκάστην αἱ πλεῖσται. διὸ τὰς μὲν ἀρχὰς τὰς περὶ ἕκαστον ἐμπειρίας ἔστι παραδοῦναι. λέγω δ’ οἷον τὴν ἀστρολογικὴν μὲν ἐμπειρίαν τῆς ἀστρολογικῆς ἐπιστήμης· ληφθέντων γὰρ ἱκανῶς τῶν φαινομένων οὕτως εὑρέθησαν αἱ ἀστρολογικαὶ ἀποδείξεις. ὁμοίως δὲ καὶ περὶ ἄλλην ὁποιανοῦν ἔχει τέχνην τε καὶ ἐπιστήμην.
What Aristotle says here — of astronomical observation and experience as furnishing the basis for astronomical science — stands in marked contrast with Plato, who rejects this basis, and puts aside, with a sort of contempt, astronomical observation (Republic, vii. pp. 530-531); treating acoustics also in a similar way. Compare Aristot. Metaphys. Λ. p. 1073, a. 6, seq., with the commentary of Bonitz, p. 506.
[65] Analyt. Prior. I. xxx. p. 46, a. 22-27: ὥστε ἂν ληφθῇ τὰ ὑπάρχοντα περὶ ἕκαστον, ἡμέτερον ἤδη τὰς ἀποδείξεις ἑτοίμως ἐμφανίζειν. εἰ γὰρ μηδὲν κατὰ τὴν ἱστορίαν παραλειφθείη τῶν ἀληθῶς ὑπαρχόντων τοῖς πράγμασιν, ἕξομεν περὶ ἅπαντος οὗ μὲν ἔστιν ἀπόδειξις, ταύτην εὑρεῖν καὶ ἀποδεικνύναι, οὗ δὲ μὴ πέφυκεν ἀπόδειξις, τοῦτο ποιεῖν φανερόν.
Respecting the word ἱστορία — investigation and record of matters of fact — the first sentence of Herodotus may be compared with Aristotle, Histor. Animal. p. 491, a. 12; also p. 757, b. 35; Rhetoric. p. 1359, b. 32.
For the fuller development of these important principles, the reader is referred to the treatise on Dialectic, entitled Topica, which we shall come to in a future [chapter]. There is nothing in all Aristotle’s writings more remarkable than the testimony here afforded, how completely he considered all the generalities of demonstrative science and deductive reasoning to rest altogether on experience and inductive observation.
We are next introduced to a comparison between the syllogistic method, as above described and systematized, and the process called logical Division into genera and species; a process much relied upon by other philosophers, and especially by Plato. This logical Division, according to Aristotle, is a mere fragment of the syllogistic procedure; nothing better than a feeble syllogism.[66] Those who employed it were ignorant both of Syllogism and of its conditions. They tried to demonstrate — what never can be demonstrated — the essential constitution of the subject.[67] Instead of selecting a middle term, as the Syllogism requires, more universal than the subject but less universal (or not more so) than the predicate, they inverted the proper order, and took for their middle term the highest universal. What really requires to be demonstrated, they never demonstrated but assume.[68]
[66] Analyt. Prior. I. xxxi. p. 46, a. 33. Alexander, in Scholia, p. 180, a. 14. The Platonic method of διαίρεσις is exemplified in the dialogues called Sophistês and Politicus; compare also Philêbus, c. v., p. 15.