The problem is, what happens if I invoke what I see in nature and explained by the theory of evolution, as the basis of some other system? For example, I could choose, "what's best for the species," or "might makes right," either of which can be defended by observable evidence, and both of which are anathema to what Rand claims.No, appealing to the behavior of other species to ground your moral code for humans is almost completely wrong. (I may say "completely wrong" after thinking about this some more.)In that case, we see that Rand's "assumptions" have some real problems -- and at the very least her system is not objective.
The proper moral system for Man is that which is compatible with our human nature. What is it that defines us? We're the rational animal. We're the ones who are able to rise above our biological heritage as an ape. We're born with precious few innate survival skills, except for one: Our rational brains.
This ability is also our necessity, since it's about all we've got going against the lions & tigers & bears (oh my). It's also what let us produce modern civilization, thus rising above the natives, Ted Kaczynski, etc. But this ability is what makes us individuals. Each one of us ends up drawing upon a myriad of shaping, instructive experiences throughout our lives, and reflecting on those experiences, as we decide for ourselves how to live.
The question now becomes: What kind of moral system best supports our innate desire to thrive, given what we know about human nature? This is true whether "our creator" was mindless, godless evolution or if we were thunk up in an instant by a bored supernatural God-person. Either way, here we are, with our big brains & not much else, wanting to know how to live. Now what do we do?
Do you see why evolution and the behavioral quirks of other species are irrelevant to this question?
In post #224, I stated I believe man's purpose is "To seek knowledge." But you just left the question hanging...
No it's not. The claim, after all, is that we must not "act Darwinian," because it's morally wrong. Well, why is it wrong, when it so clearly works well for other species? What is it about our (evolved) brains that automatically excludes us from Might Makes Right?
On what basis can you justify the fact that "decid[ing] for ourselves how to live" must exclude my taking advantage of those weaker than I am?
The answer boils down to this: because you said so.
This is an argument from results -- but results are not an objective measure of absolute right vs. everything else. In fact, it is an admission that you're comparing different sets of valid alternatives, and choosing the "best" of them according to some subjective measure. In that case, "objectivism" reduces to utilitarianism.