5. Petitio Principii.
6. Non Causa pro Causâ.
7. Fallacia Plurium Interrogationum.[27]
[27] Soph. El. v. p. 166, b. 20-27.
1. The first of these varieties, called Fallacia Accidentis, arises when a syllogism is made to conclude that, because a given predicate may be truly affirmed of a given subject, the same predicate may also be truly affirmed respecting all the accidents of that subject: as when Koriskus is denied to be a man, because he is not Sokrates, who is a man; or is denied to be Koriskus, because he is a man, while a man is not Koriskus.
In the title given to this general head of Fallacy,[28] we must understand Accident, not in its special logical sense as opposed to Essence, but in a far larger sense, including both Genus when predicated separately from Differentia, and Differentia when predicated separately from Genus; including, in fact, every thing which is distinguishable from the subject in any way, and at the same time predicable of it — every thing except the Definition, which conjoins Genus and Differentia together, and is thus identical and convertible with the definitum.
[28] Ibid. b. 29: οἱ παρὰ τὸ συμβεβηκὸς παραλογισμοί. Every man is an animal; but, because a predicate is true of the subject man, you cannot infer that the same predicate is true of the subject animal. This title comprehends within its range another, which is presently announced as distinct and separate — Fallacia Consequentis.
2. The second general variety arises when a proposition is affirmed with qualification or limitation in the premisses, but is affirmed without qualification, simply and absolutely, in the conclusion. The Ethiopian is white in his teeth and black in his skin; therefore, he is both white and not white — both white and black. In this example the fallacy is obvious, and can hardly escape any one; but there are many other cases in which the distinction is not so conspicuous, and in which the respondent will hesitate whether he ought to grant or refuse a question simply and absolutely.[29] One example given by Aristotle deserves notice on its own account: Non-Ens est opinabile, therefore Non-Ens est; or, again, Ens non est homo, therefore, Ens non est. This is one among Aristotle’s ways of bringing to view what modern logicians describe as the double function of the substantive verb — to serve as copula in predication, and to predicate existence.[30] He regards the confusion between these two functions as an example of the Fallacy now before us — of passing a dicto Secundum Quid ad dictum Simpliciter.[31]
[29] Ibid. b. 37, seq. ὅταν τὸ ἐν μέρει λεγόμενον ὡς ἁπλῶς εἰρημένον ληφθῇ — τὸ δὲ τοιοῦτον ἐπ’ ἐνίων μὲν παντὶ θεωρῆσαι ῥᾴδιον — ἐπ’ ἐνίων δὲ λανθάνει πολλάκις.
[30] The same double or multiple meaning of Est is discriminated by Aristotle in the Metaphysica, but in a different way — τὸ ὂν ὡς ἀληθές, καὶ τὸ μὴ ὂν ὡς ψεῦδος — Δ. vii. p. 1017, a. 31; E. iv. p. 1027, b. 18-36. Bonitz (ad. Metaphys. Z. iv. p. 310) says:— “Quid quod etiam illud esse huc refert, quo non existentiam significamus, sed predicati cum subjecto conjunctionem.â€� Aristotle is even more precise than modern logicians in analysing the different meanings of τὸ ὄν: he distinguishes four of them.