[312] Topic. VI. ix. p. 147, b. 4-25.
24. When the definiend is a Privative Term, the definition given ought to enunciate that which it is, and that of which it is the privation; also that subject in which it resides naturally and in the first instance. In defining ignorance, the definition must enunciate not privation only, but privation of knowledge; nor will this be sufficient unless it be added that the privation of knowledge is in the rational department of the soul (ἐν τῷ λογιστικῷ). Privation of knowledge in the soul or in the man, will not suffice; because neither of these subjects is that in which the attribute resides in the first instance: the rational department of the soul must be named by itself, as being the primary subject of the attribute. If the definition be wanting in any of these conditions, you will have an argument for impeaching it.[313]
[313] Ibid. b. 26-p. 148, a. 2.
25. A term that is privative in form may sometimes be used in the sense of mere negation, not in that of privation. If this term be defined generally by privation, the definition will not include the merely negative sense, and will therefore be impeachable. The only general explanation attainable is that by pure negation, which is common both to the negative and the privative. Thus, if the respondent defines ignorance — privation of knowledge, such privation can be predicated only of subjects whose nature it is to have knowledge or who might be expected to have it: such privation cannot be predicated of infants, or of inanimate objects like stones. To include these, ignorance must be explained as the mere negation or non-existence of knowledge; the definition thereof by privation is inadequate.[314]
[314] Ibid. p. 148, a. 3-9: ὁρᾶν δὲ καὶ εἰ μὴ λεγομένου κατὰ στέρησιν στερήσει ὡρίσατο, οἷον καὶ ἐπὶ τῆς ἀγνοίας δόξειεν ἂν ὑπάρχειν ἡ τοιαύτη ἁμαρτία τοῖς μὴ κατ’ ἀπόφασιν τὴν ἄγνοιαν λέγουσιν.
Waitz says in note, p. 503:— “Sensus loci hic est. Peccant qui per privationem ignorantiam definientes non eam ignorantiam definire voluerunt quæ est κατ’ ἀπόφασιν, sed eam quæ est κατὰ διάθεσιν.â€� Compare Analyt. Poster. I. xvi. p. 79, b. 23.
26. If you are debating with one who holds the Platonic doctrine of Ideas, you will note whether any definition that he may give fits not only the definiend itself but also the Idea of the definiend. Thus, Plato in defining animal introduces mortality as a part of his definition;[315] but mortality cannot be predicated of the Idea or generic animal — the Self-animal; therefore, you will have an argument against his definition. In like manner, if any active or passive attribute is brought into his definition, you will object that this cannot apply to the Ideas; which are avowedly impassive and unchangeable.[316]
[315] Topic. VI. x. p. 148, a. 15: οἷον ὡς Πλάτων ὁρίζεται τὸ θνητὸν προσάπτων ἐν τοῖς τῶν ζῴων ὁρισμοῖς.
This may perhaps allude to Plato’s manner of speaking of ζῷα in Sophistes, p. 246, E., p. 265, C.; Timæus, p. 69, C.
[316] Topica, VI. x. p. 148, a. 14-22. ἀπαθεῖς γὰρ καὶ ἀκίνητοι δοκοῦσιν αἱ ἰδέαι τοῖς λέγουσιν ἰδέας εἶναι.