Free choice

For an external observer (say, an alien), is it correct to assume that there is no free choice?
First of all, why would he think about free choice at all? And if he did, according to Occam’s razor, a mechanistic explanation is of course preferable to adding an unknown and inexplicable primary force.
(As humans, of course we can argue about subjective experience, and perhaps aliens can incorporate this into their calculations. Perhaps also reach a conclusion about the truth of the Torah and therefore about free choice. But I want to understand whether determinism should indeed be assumed at the base)