If determinism exists, then the whole of the future must existent somewhere. Some would argue that the 4th dimension or God holds that knowledge. I would disagree and say that that knowledge doesn’t exist anywhere or is unlikely to and thus are actions are not determined. I can never prove the existence of freewill. Thus I resort to coming up with strong arguments disproving the existence of determinism.
I would further argue that even if God or the 4th dimension or the knowledge of the consequences of our actions did exist, I as a person and we as humankind don’t have access to that knowledge and thus I feel like I have freewill (which for me feels the same as actually having freewill). Therefore, go freewill!