It is a scientific fact. We definitely live in a deterministic universe - all branches of science confirm this. Well I think there's some dwindling hope for non-determinism in some interpretations of quantum physics.

At the moment the debate is between hard determinism and compatiblism, which states that the universe is deterministic but we can still meaningfully talk about free will, because even though it's an illusion our brains create, the fact that our brains create this illusion makes it real enough for our purposes.