Rhet gre 1397a8-9(8) δεῖ γὰρ σκοπεῖν εἰ τῷ ἐναντίῳ τὸ ἐναντίον ὑπάρχει, ἀν(9)αιροῦντα μὲν εἰ μὴ ὑπάρχει, κατασκευάζοντα δὲ εἰ ὑπάρχει,
Rhys Roberts 1924 engPart 23. 1. One line of positive proof is based upon consideration of the opposite of the thing in question.
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