Yes that line of logic works. Proof by contradiction uses this idea.Are the only two ways to prove that the If-then statement is true is to show that for any P, Q must be the consequent?

I've heard that another way to prove that the statement is true is to show that for any ~Q, the consequent must be ~P. That is, if we show that If ~Q then ~P is true, then we can conclude If P then Q is true.