contrapositive

In the case of the I proposition the contrapositive is impossible, as infringing the main rule of conversion.

Every positive in thought has a contrapositive, and the positive and contrapositive are of the same kind.

But take the obverse of the contrapositive of both premises: All m is p; All m is s: ∴ Some s is p.

As before, the conclusion in the constructive type resolves itself into the subalternate of the major itself, and in the destructive type into the subalternate of its contrapositive.

Every impression felt is felt as a change or transition from something else: but it is a variation of the same impression—the something else, the contrapositive, is not entirely different.