The second schemata is today known as modus tollendo tollens. Its form is as follows: If p, then q; not q; therefore, not-p. For this schemata, the conditional and the contradiction of its consequence as premises. From that, the contradiction of the antecedent follows as the conclusion. I will provide a brief example. 1) If I am going to the car wash, then my car will be cleaned. 2) My car will not be cleaned (or not-my car will be cleaned. 2) Therefore, I am not going to the car wash (or not-I am going to the car wash).
