Connexive class logic
Storrs McCall · Journal of Symbolic Logic · 1967
Student. I've been studying the logic of classes, and can't see how any class can be included in its own complement. Teacher. Surely you've heard of the null class, which is included in every class, and hence in its own complement? Student. That also strikes me as somehow implausible. How do you define ‘inclusion’? Teacher. In the usual way. a is included in b if and only if the intersection of a with the complement of b is null.