Such is the capital antithesis, much dwelt upon by Aristotle, between Didactic and Dialectic. But that which he calls Peirastic, and that which he calls Eristic, are not species co-ordinate with and distinguished from Dialectic: they are peculiar aspects, subordinate varieties or modes, of Dialectic itself. Aristotle himself, indeed, admits Peirastic to be a mode or variety of Dialectic;[6] and the like is equally true respecting what he terms Eristic or Sophistic.
[6] Soph. El. xi. p. 171, b. 4-9: ἡ γὰρ πειραστική ἐστι διαλεκτική τις, &c. — p. 172, a. 35: ὁ τέχνῃ συλλογιστικῇ πειραστικός, διαλεκτικός. — viii. p. 169, b. 25: ἔστι δ’ ἡ πειραστικὴ μέρος τῆς διαλεκτικῆς.
These subordinate distinctions turn upon the manner, the limitations, and the purpose, for and under which the dialectical process is conducted. Dialectic is essentially gymnastic and peirastic:[7] it may be looked at either as gymnastic, in reference to the two debaters, or as peirastic, in reference to the arguments and doctrines brought forward; intellectual exercise and stimulation of the two speakers and the auditors around being effected by testing and confronting various probable doctrines. It is the common purpose (κοινὸν ἔργον)[8] of the two champions, to improve and enlarge this exercise for the instruction of all, by following out a variety of logical consequences and logical repugnancies, bearing more or less directly on the thesis which the respondent chooses and undertakes to defend against a testing cross-examination. Certain rules and limitations are prescribed both for questioner and respondent; but, subject to these rules, each of them is bound to exert all his acuteness for the purpose of gaining victory; and, though one only can gain it, the debate may be well and creditably conducted on both sides. If the rules are not observed, if the assailing champion, bent upon victory at all cost, has recourse to dishonest interrogative tricks, or the defensive champion to perverse and obstructive negations, beyond the prescribed boundary, in that case the debate is called by Aristotle eristic or contentious, from the undue predominance of the controversial spirit and purpose; also sophistic, from the fact that there existed (as he asserts) a class or profession of persons called Sophists, who regularly studied and practised these culpable manÅ“uvres, first with a view to reputation, and ultimately with a view to pecuniary profit, being pretenders to knowledge and wisdom without any reality to justify them.[9]
[7] Topic. I. ii. p. 101, a. 26, b. 2: πρὸς γυμνασίαν — ἐξεταστικὴ γὰρ οὖσα, &c. Compare also Topica, VIII. xi. p. 161, a. 25; xiv. p. 163, a. 29, p. 164, b. 1: τὸ δὲ γυμνάζεσθαι δυνάμεως χάριν, καὶ μάλιστα περὶ τὰς προτάσεις καὶ ἐνστάσεις· ἔστι γὰρ ὡς ἁπλῶς εἰπεῖν διαλεκτικὸς ὁ προτατικὸς καὶ ἐνστατικός.
[8] Topic. VIII. xi. p. 161, a. 20, 37.
[9] Soph. El. xi. p. 171, b. 25-35: οἱ μὲν οὖν τῆς νίκης αὐτῆς χάριν τοιοῦτοι ἐριστικοὶ ἄνθρωποι καὶ φιλέριδες δοκοῦσιν εἶναι, οἱ δὲ δόξης χάριν τῆς εἰς χρηματισμὸν σοφιστικοί· — καὶ τῶν λόγων τῶν αὐτῶν μέν εἰσιν οἱ φιλέριδες καὶ σοφισταί, ἀλλ’ οὐ τῶν αὐτῶν ἕνεκεν. καὶ λόγος ὁ αὐτὸς μὲν ἔσται σοφιστικὸς καὶ ἐριστικός, ἀλλ’ οὐ κατὰ ταυτόν, ἀλλ’ ᾗ μὲν νίκης φαινομένης, ἐριστικός, ᾗ δὲ σοφίας, σοφιστικός. &c.
We thus see plainly that Peirastic and Eristic are not to be ranked as two distinct species of discourse, co-ordinate with Didactic and Dialectic; but that peirastic is in fact an epithet applicable generally to Dialectic, bringing to view one of its useful and appropriate functions; while eristic designates only a peculiar mode of conducting the process, the essential feature of which is that it is abusive or that it transgresses the rules and regulations. Still less ought Sophistic to be ranked as a distinct species; since it involves no intrinsic or intellectual differentia, but connotes only ethical and personal peculiarities ascribed to the Sophist, who is treated as an impostor practising dishonest tricks for the sake of pecuniary profit.[10]
[10] Aristot. Rhetoric. I. i. p. 1355, b. 17: ὁ γὰρ σοφιστικὸς οὐκ ἐν τῇ δυνάμει, ἀλλ’ ἐν τῇ προαιρέσει· — σοφιστὴς μὲν κατὰ τὴν προαίρεσιν, διαλεκτικὸς δ’ οὐ κατὰ τὴν προαίρεσιν ἀλλὰ κατὰ τὴν δύναμιν. To the same purpose he speaks in Metaphys. Γ. ii. p. 1004, b. 25, distinguishing the Sophist by his προαίρεσις from the Dialectician, but recognizing that in point of δύναμις both are alike. Mr. Poste observes justly (in Transl. of the Soph. El., notes, p. 99):— “δύναμις, capacity, is in the intellect; προαίρεσις, purpose, in the will. The antithesis between these terms may throw light on what Aristotle conceived to be the relation between Sophistic and Dialectic.… The power plus the will to deceive is called Sophistic; the power without the will, Dialectic (p. 100).â€�
While, however, we recognize as main logical distinctions only the two heads Didactic and Dialectic, we note another way that Aristotle has of bringing in what he calls Sophistic as a variety of the latter. Both in Didactic and Dialectic (he tells us) the speakers enunciate and prove their propositions by Syllogism; the didactic syllogism is derived from the principia belonging specially to one particular science, and proceeds from premisses that are true to conclusions that are true; while the dialectic syllogism starts from probable premisses (i.e., accredited by the ordinary public or by a few wise men), and marches in correct form to conclusions that are probable. Now, corresponding to each of these two, Aristotle recognizes farther a sort of degenerate counterpart. To the didactic syllogism there corresponds the pseudographic syllogism or the paralogism: which draws its premisses (as the didactic syllogism does) from the special matters of some given science,[11] yet which nevertheless has only the appearance of truth without the reality; either because it is incorrect in syllogistic form, or because the matter of the premisses (the major, the minor, or both) is untrue. To the dialectic syllogism in like manner, there corresponds the eristic or sophistic syllogism: which is a good syllogism in appearance, but not in reality; either because it is incorrect in form, or because its premisses, in respect of their matter, appear to be probable without being really probable.[12]
[11] Topic. I. i. p. 101, a. 5-15. οἱ ἐκ τῶν περί τινας ἐπιστήμας οἰκείων γινόμενοι παραλογισμοί, καθάπερ ἐπὶ τῆς γεωμετρίας καὶ τῶν ταύτῃ συγγενῶν συμβέβηκεν ἔχειν· — ἐκ τῶν οἰκείων μὲν τῇ ἐπιστήμῃ λημμάτων, οὐκ ἀληθῶν δέ, τὸν συλλογισμὸν ποιεῖται.