How about one that has demonstrated its robustness over several hundred million years -- Survival of the Fittest? Or its companion, Might Makes Right? (After all, we can see that the strongest tend to be the fittest.)
True, these ideas are not particularly kind to the idea of liberty, but they do seem to meet the evidentiary standards that Rand would demand of an objective philosophy.
Actually, I suscribe the the opposite position: Right makes Might. Right attracts; wrong repels. Strength in numbers as it were. Liberty attracts; slavery repels. That is why America, based, comparatively at least, in liberty is mighty.