  and at least some of them were regarded as reducible to Aristotle’s categorical syllogisms, presumably by way of the equivalences to ‘Every A is B’, etc. In parallel to Aristotle’s syllogistic, Theophrastus distinguished three figures; each had sixteen modes. The first eight modes of the first figure are obtained by going through all permutations with ‘not X’ instead of ‘X’ (with X for A, B, C); the second eight modes are obtained by using a rule of contraposition on the conclusion: