Philosopher Barry Smith has argued in several places (see “The Question of Apriorism,” for an example), contra the Austrian economists, that the action axiom is not irrefutable. He points out that an alien could deny that human beings act. I think that he is correct here if the action axiom is defined as the fact that human beings act. But even so, any attempt by a human being to refute the action axiom would still be self-defeating. In any case, I would argue (as I believe notable Austrian economists have) that the action axiom is universalizable to all volitional beings, in which case a denial by an alien that human beings act would hinge upon an empirical-contingent claim, viz. the denial that human beings are volitional beings. The truth of the action axiom is thus never in question, and it remains irrefutable.