Chapter 63

One should know that the affirmation and the negation are called statements. An affirmation is that statement which signifies what belongs to someone, or what someone is, for example: Socrates is wise, Socrates walks. A negation, on the other hand, is that which shows what does not belong to someone, or what someone is not, for example: So-and-so is not wise, so-and-so does not walk. Since a negation is opposed to every affirmation and an affirmation to every negation, the negation opposed to the affirmation and the affirmation opposed to the negation are called contradictions. One of these, moreover, must necessarily be false and one true.

[50] {Περὶ ἀποφάνσεως ἀποφάσεώς τε καὶ καταφάσεως.} Χρὴ γινώσκειν, ὅτι ἡ κατάφασις καὶ ἡ ἀπόφασις ἀπόφανσις λέγεται. Κατάφασις μὲν οὖν ἐστιν ἡ σημαίνουσα, τί τινι ὑπάρχει, τουτέστι τί ὑπάρχει τις: οἷον ‘Σωκράτης σοφός ἐστι’, ‘Σωκράτης περιπατεῖ’. Ἀπόφασις δὲ ἡ δηλοῦσα τὸ μὴ ὑπάρχον τινὶ ἤγουν τί οὐκ ἔστι τις, οἷον ‘ὁ δεῖνα οὐκ ἔστι σοφός’, ‘ὁ δεῖνα οὐ περιπατεῖ’. Ἐπειδὴ δὲ πάσῃ καταφάσει ἀντίκειται ἀπόφασις καὶ πάσῃ ἀποφάσει κατάφασις, ἡ ἀπόφασις ἡ ἀντικειμένη τῇ καταφάσει καὶ ἡ κατάφασις ἡ ἀντικειμένη τῇ ἀποφάσει ἀντίφασις λέγεται: ἀνάγκη δὲ τὴν μίαν ψεύδεσθαι καὶ τὴν μίαν ἀληθεύειν.