All of economic science rests upon its foundation as “a priori” or deductive knowledge as opposed to “a posteriori” or inductive knowledge. Free trade follows logically from the irrefutable maxims that “man acts” and that “man owns himself”. These maxims cannot be refuted by so-called “evidence” to the contrary. Great economic laws, such as David Ricardo’s “Law of Comparative Advantage”, Jean Baptiste Say’s “Law of Markets”, and Frederic Bastiat’s “That Which Is Seen, and That Which Is Not Seen” follow. No a posteriori/inductive evidence can prove these conclusions to be in error. The common objections that free trade causes unemployment and that free trade harms essential industries are presented and refuted.