How is free will proven? It seems to me that Occam’s razor leads one to assume determinism is more likely correct than idealism. But yes, determinism is assumed to be true, but that assumption is based on evidence.

Does proving determinism require complete predictability? — Ree Zen

Not necessarily. If you have a specific instance of matter interacting in a causal way with other objects, is it reasonable to conclude that all matter interacts in this way? How many objects do I need to drop before I can “prove” gravity exists?

Some actions are predictable, but some are not. — Ree Zen

This is likely, in my opinion, due to our lack of knowledge regarding those particular actions. We’re not entirely sure how the brain works, so any act presumably caused by brain states is destined to have a certain amount of uncertainty involved.