 Yet this account of the ekthesis proof is not without its problems. Even in antiquity, Aristotle was accused of arguing in a circle, since (1:6) and (1:7) seem to correspond to the third figure incomplete syllogisms Darapti and Felapton. (1:4)–(1:7) also seem superfluous, and in fact Alexander of Aphrodisias (fl. c. 200 AD) was able to show that ekthesis is really all Aristotle needed, since all the valid moods can be proved with it. Aristotle also used counterexamples to show that a mood is invalid.