Schemata four is today called modus ponendo tollens. Its form is as follows: Either p or q; p; therefore, not-q. For example, 1) Either I will go to college or I will work in my parents’ bakery. 2) I will work in my parents’ bakery. 3) Therefore, I will not go to college (or not-I will go to college). In this schemata a disjunction and one of its disjuncts are premises. The conclusion then is the contradiction of the remaining disjunct.
