The manner in which the Platonic Sokrates proves (Theæt. 165) that you at the same time see, and do not see, an object before you, is quite as sophistical as the way in which Eubulidês proves that you both know, and do not know, your father.
Causes of error constant — the Megarics were sentinals against them.
The causes of error and fallacy are inherent in the complication of nature, the imperfection of language, the small range of facts which we know, the indefinite varieties of comparison possible among those facts, and the diverse or opposite predispositions, intellectual as well as emotional, of individual minds. They are not fabricated by those who first draw attention to them.[51] The Megarics, far from being themselves deceivers, served as sentinels against deceit. They planted conspicuous beacons upon some of the sunken rocks whereon unwary reasoners were likely to be wrecked. When the general type of a fallacy is illustrated by a particular case in which the conclusion is manifestly untrue, the like fallacy is rendered less operative for the future.
[51] Cicero, in his Academ. Prior, ii. 92-94, has very just remarks on the obscurities and difficulties in the reasoning process, which the Megarics and others brought to view — and were blamed for so doing, as unfair and captious reasoners — as if they had themselves created the difficulties — “(Dialectica) primo progressu festivé tradit elementa loquendi et ambiguorum intelligentiam concludendique rationem; tum paucis additis venit ad soritas, lubricum sané et periculosum locum, quod tu modo dicebas esse vitiosum interrogandi genus. Quid ergo? istius vitii num nostra culpa est? Rerum natura nullam nobis dedit cognitionem finium, ut ullâ in re statuere possimus quatenus. Nec hoc in acervo tritici solum, unde nomen est, sed nullâ omnino in re minutatim interroganti — dives, pauper — clarus, obscurus, sit — multa, pauca, magna, parva, longa, brevia, lata, angusta, quanto aut addito aut dempto certum respondeamus, non habemus. At vitiosi sunt soritæ. Frangite igitur eos, si potestis, ne molesti sint.… Sic me (inquit) sustineo, neque diutius captiosé interroganti respondes. Si habes quod liqueat neque respondes, superbis: si non habes, ne tu quidem percipis.”
The principle of the Sorites (ἡ σωριτικὴ ἀπορία — Sextus adv. Gramm. s. 68), though differently applied, is involved in the argument of Zeno the Eleate, addressed to Protagoras — see Simplikius ad Aristot. Physic. 250, p. 423, b. 42. Sch. Brand. Compare [chap. ii.] of this volume.
Controversy of the Megarics with Aristotle about Power. Arguments of Aristotle.
Of the positive doctrines of the Megarics we know little: but there is one upon which Aristotle enters into controversy with them, and upon which (as far as can be made out) I think they were in the right. In the question about Power, they held that the power to do a thing did not exist, except when the thing was actually done: that an architect, for example, had no power to build a house, except when he actually did build one. Aristotle controverts this opinion at some length; contending that there exists a sort of power or cause which is in itself irregular and indeterminate, sometimes turning to the affirmative, sometimes to the negative, to do or not to do;[52] that the architect has the power to build constantly, though he exerts it only on occasion: and that many absurdities would follow if we did not admit, That a given power or energy — and the exercise of that power — are things distinct and separable.[53]
[52] Aristot. De Interpret. p. 19, a. 6-20. ὅλως ἔστιν ἐν τοῖς μὴ ἀεὶ ἐνεργοῦσι τὸ δυνατὸν εἶναι καὶ μὴ ὁμοίως· ἐν οἷς ἀμφω ἐνδέχεται, καὶ τὸ εἶναι καὶ τὸ μὴ εἶναι, ὥστε καὶ τὸ γενέσθαι καὶ τὸ μὴ γενέσθαι.
[53] Aristot. Metaph. Θ. 3, p. 1046, b. 29. Εἰσὶ δέ τινες, οἴ φασιν, οἷον οἱ Μεγαρικοί, ὅταν ἐνεργῇ, μόνον δύνασθαι, ὅταν δὲ μὴ ἐνεργῇ, μὴ δύνασθαι — οἷον τὸν μὴ οἰκοδομοῦντα οὐ δύνασθαι οἰκοδομεῖν, ἀλλὰ τὸν οἰκοδομοῦντα ὅταν οἰκοδομῇ· ὁμοίως δὲ καὶ ἐπὶ τῶν ἄλλων.
Deycks (De Megaricorum Doctrinâ, pp. 70-71) considers this opinion of the Megarics to be derived from their general Eleatic theory of the Ens Unum et Immotum. But I see no logical connection between the two.