I was delighted to see the announcement of the conference to which you contributed in this area last month at Bowling Green. I think some other readers here would also be pleased to know that such a conference was held, so I will display some of the presenters and their topics in a subsequent post to this thread.
Within your note here, you posed the question of whether humans are “pretty much living and thinking beings without any choice to be such.” You remarked that if this were so, “then it would seem that the principles of ethics are binding on them independently of any choice, as a necessary and not conditional aspect of their lives.” You then asked, “Why would Rand think that this isn't the case?”
I assume you are also asking (i) why Rand did not and should not think that principles of ethics are binding on us independently of some sort of choice to live and think and (ii) what sound reasons there are—not only for Rand, but for anyone—to think that principles of ethics are not binding on us independently of some sort of choice to live and think.
You then write:
Before answering that question, it bears noting that conditional principles can be every bit as objective as unconditional ones. For example, let us take it that the principle of gravitation is unconditional, necessary (although in some very broad metaphysical sense it might well be—if no objects with mass existed, there would be no gravitation). Let us also take it that the principles of mechanical engineering are conditional—unless people wanted to build things, there would be no such principles (only potentially).
The last proposition incorrect. Physical principles of engineering are not more conditional on the existence of humans wanting to build things than are scientific laws conditional on the existence of humans wanting to build things.
Usefulness of a physical principle does not make it more conditional. The Law of the Lever is not more conditional than Hawking’s Evaporative Radiation Law for Black Holes. In addition the fact that a physical entity or system is a human invention does not mean that its principles are more conditional on human intelligence than would be a naturally occurring entity or system. The Fullerene molecule was a human invention of the early 90s. We later discovered that it also occurs naturally.