So what? Why should an a priori proof of the libertarian property theory make any difference? Why not engage in aggression anyway?” Why indeed?! But then, why should the proof that 1+1=2 make any difference? One certainly can still act on the belief that 1+1=3. The obvious answer is “because a propositional justification exists for doing one thing, but not for doing another.” But why should we be reasonable, is the next come-back. Again, the answer is obvious. For one, because it would be impossible to argue against it; and further, because the proponent raising this question would already affirm the use of reason in his act of questioning it. This still might not suffice and everyone knows that it would not, for even if the libertarian ethic and argumentative reasoning must be regarded as ultimately justified, this still does not preclude that people will act on the basis of unjustified beliefs either because they don’t know, they don’t care, or they prefer not to know. I fail to see why this should be surprising or make the proof somehow defective.