I argue that Aristotle’s late-antique commentators read into his theory of demonstration the notion of tekmeriodic proofs in attempt to integrate into the theory of demonstration the assumption that the principles of demonstration should be evident. In so doing, I trace the late antique commentators’ view to Alexander of Aphrodisias’ discussion of the principles of demonstration, showing how his assumption that the principles of demonstration should be evident underlies their notions of tekmeriodic proofs.