Aristotle: Analytica Priora (Prior Analytics)

στρέφειν πρὸς ἄμφω. Εἰ γὰρ τὸ Α κατὰ τοῦ Γ διὰ τοῦ Β ὑπάρχει, εἰ ἀντιστρέφει καὶ ὑπάρχει, ᾧ τὸ Α, παντὶ τὸ Γ, καὶ τὸ Β τῷ Α ἀντιστρέφει, καὶ ὑπάρχει, ᾧ τὸ Α, παντὶ τὸ Β διὰ μέσου τοῦ Γ, καὶ τὸ Γ τῷ Β ἀντιστρέφει διὰ μέσου τοῦ Α. Καὶ ἐπὶ τοῦ μὴ ὑπάρχειν ὡσαύτως, οἷον εἰ τὸ Β τῷ Γ ὑπάρχει, τῷ δὲ Β τὸ Α οὐχ ὑπάρχει, οὐδὲ τὸ Α τῷ Γ οὐχ ὑπάρξει. Εἰ δὴ τὸ Β τῷ Α ἀντιστρέφει, καὶ τὸ Γ τῷ Α ἀντιστρέψει. Ἔστω γὰρ τὸ Β μὴ ὑπάρχον τῷ Α· οὐδ᾿ ἄρα τὸ Γ· παντὶ γὰρ τῷ Γ τὸ Β ὑπῆρχεν. Καὶ εἰ τῷ Β τὸ Γ ἀντιστρέφει, καὶ τῷ Α ἀντιστρέφει· καθ᾿ οὗ γὰρ ἅπαντος τὸ Β, καὶ τὸ Γ.᾿ Καὶ εἰ τὸ Γ πρὸς τὸ Α ἀντιστρέφει, καὶ τὸ Β ἀντιστρέφει πρὸς τὸ Α. Ὧ γὰρ τὸ Β, τὸ Γ· ᾧ δὲ τὸ Γ, τὸ Α οὐχ ὑπάρχει. Καὶ μόνον τοῦτο ἀπὸ τοῦ συμπεράσματος ἀρχεται, τὰ δ᾿ ἄλλα οὐχ ὁμοίως καὶ ἐπὶ τοῦ κατηγορικοῦ συλλογισμοῦ. Πάλιν εἰ τὸ Α καὶ τὸ Β ἀντιστρέφει, καὶ τὸ Γ καὶ τὸ Δ ὡσαύτως, ἅπαντι δ᾿ ἀνάγκη τὸ Α ἢ τὸ Γ ὑπάρχειν, καὶ τὸ Β καὶ Δ οὕτως ἕξει ὥστε παντὶ θάτερον ὑπάρχειν. Ἐπεὶ γὰρ ᾧ τὸ Α, τὸ Β, καὶ ᾧ τὸ Γ, τὸ Δ, παντὶ δὲ τὸ Α ἢ τὸ Γ καὶ οὐχ ἅμα, φανερὸν ὅτι καὶ τὸ Β ἢ τὸ Δ παντὶ καὶ οὐχ ἅμα. Οἷον εἰ τὸ ἀγένητον ἄφθαρτον καὶ τὸ ἄφθαρτον ἀγένητον, ἀνάγκη τὸ γένομενον φθαρτὸν καὶ τὸ φθαρτὸν γεγονέναι· δύο γὰρ συλλογισμοὶ σύγκεινται. Πάλιν εἰ παντὶ μὲν τὸ Α ἢ τὸ Β καὶ τὸ Γ ἢ τὸ Δ, ἅμα δὲ μὴ ὑπάρχει, εἰ ἀντιστρέφει τὸ Α καὶ τὸ Γ, καὶ τὸ Β καὶ τὸ Δ ἀντιστρέφει. Εἰ γὰρ τινὶ μὴ ὑπάρχει τὸ Β, ᾧ τὸ Δ, δῆλον ὅτι τὸ Α ὑπάρχει. Εἰ δὲ τὸ Α, καὶ τὸ Γ· ἀντιστρέφει γάρ. Ὥστε ἅμα τὸ Γ καὶ Δ. Τοῦτο δ᾿ ἀδύνατον. Ὅταν δὲ τὸ Α ὅλῳ τῷ Β καὶ τῷ Γ ὑπάρχῃ καὶ μηδενὸς ἄλλου κατηγορῆται, ὑπάρχῃ δὲ καὶ τὸ Β παντὶ τῷ Γ, ἀνάγκη τὸ Α καὶ Β ἀντιστρέφειν· ἐπεὶ γὰρ κατὰ μόνων τῶν Β Γ λέγεται τὸ Α, κατηγορεῖται δὲ τὸ Β καὶ αὐτὸ αὑτοῦ καὶ τοῦ Γ, φανερὸν ὅτι καθ᾿ ὧν τὸ Α, καὶ