Thus, if non-initiation of force is to be accepted as absolute, the basis for making the claim must come from a source other than application of reason -- from God, for example.
When you get right down to it, the problem is in the claims of absoluteness: they cannot be proved by this allegedly logical philosophy. And without such proof, the foundation of objectivism collapses.
I don't understand what you're getting at here. All knowledge includes assumptions at its base. By definition, assuptions are not proved. If you don't believe the assumptions, all that's built upon them is suspect, but nonproveable assumptions there must be.
Even in mathematics, agruably our most pure knowledge, there are plenty of assumptions. Under certain perfectly valid assumptions, 2+2 is not 4.
Christianity begins with the assumption that God exists. No proof is offered. A second assumption is that the Bible is the Word of God. Again, not proved anywhere.
Very true, but that kills the notion that objectivism is the only "logical" system of philosophy. If you accept the premises as axioms, then you can construct the objectivist system in a perfectly logical manner, but since there's no way to prove the axioms, there's no real reason to accept the axioms of objectivism over some other set of axioms. And if I then choose to substitute some other set of unprovable axioms - such as "God exists and he says X is wrong" - then I can construct some completely different system in a perfectly logical manner, just as logically as I can construct the objectivist philosophy.
No philosophy is completely self-contained and completely provable - it can't be, as you quite rightly point out. That doesn't make objectivism inherently inferior to other philosophies, but it ends any nonsense about it being inherently superior.
Right. But Rand claims claims that her assumptions are correct, and that all others are wrong -- which implies that she's got some means of proving her unprovable assumptions.
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.
In that case, we see that Rand's "assumptions" have some real problems -- and at the very least her system is not objective.
Christianity follows up with the claim that God reveals his existence to us -- which relieves us as individuals from the problem of evidentiary proof. Christianity also claims that God reveals His will to us, and that the Bible represents a compilation of revelations.
Be that as it may, the role of God in this argument is as the source of truth. To wit: given that we cannot demonstrate the proof of our assumptions, the only way we know they're true is if some unassailable authority tells us that they're true.