Transposition involves "flipping the arguments" of a conditional around, as
well as "inverting their sign," i.e., negating them. So, to verify
this rule at the top level, we just check that both propositions are
conditionals, and that the second operand of one is the negation of the
first operand of the other, and vice versa.
Transposition involves "flipping the arguments" of a conditional around, as well as "inverting their sign," i.e., negating them. So, to verify this rule at the top level, we just check that both propositions are conditionals, and that the second operand of one is the negation of the first operand of the other, and vice versa.