[Physicist]

I assert that we cannot say something is random in the system without knowing what the system "is".

Fair enough. But experiments reveal something about what the system is NOT. It is NOT deterministically causal; any such system is constrained to respect Bell's Inequality, which the universe sometimes does not. There are also valid interpretations that involve information propagating backwards in time, and the like.

[Alamo-Girl]

Thank you so much for your reply and acceptance! I of course agree with you that we can speak to what the system (in this case, space/time) is not - but, not yet, what it fully "is".