Do you think we have free will to make choices or do you think that fate/God is controlling everything we do? In other words, can we make our own choices or is everything we will ever do already been decided upon by God and we are just acting out what has been written on the Tablet of Fate? Are we all just actors in a movie that God has scripted?
Not that im an expert on what im about to say, so it might be wrong. But I think we can make some thought experiments about it at least.
Unless God intervene in our lives, I don't think it would make any difference in regards to free will, whether he existed or not.
To keep it simple, let's say that we knew exactly what our Universe were made of and we had a supercomputer with unlimited capacity to calculate things for us. Now imagine our Universe like this:
Where the top left image would be the beginning of the universe and the bottom right some undefined ending in the future. If we take a picture in the middle somewhere and say that this is where we are now. Then we could in theory predict what would happen in the future, if we knew everything about the former state everything that made up the Universe were in, so predicting ahead one billions of a second, we could calculate exactly how it would look. The only stage which we couldn't predict would be the very first one, because here we would have no pass data to make predictions from, meaning that the first image could jump directly to the third image, rather than the second. However since we are not at the first image, we already know what happened at that point, so if we reversed the universe, we would get back to the beginning, and if we forwarded again, we would end up the exact same place. And forward a bit more and we could predict the future.
This would obviously mean that we wouldn't have free will, because everything is determined by the former events. Hench the idea of determinism.
However this is where things gets a bit complicated
Because in the example above I just assumed that we could know everything about everything, but it turns out from what I can understand, that we can't know everything, quantum mechanics seems to cause some issues here, as we have to rely on probabilities.
Predictions of quantum mechanics have been verified experimentally to an extremely high degree of accuracy. A fundamental feature of the theory is that it usually cannot predict with certainty what will happen, but only give probabilities.
Again im no expert in this and it is just a thought experiment
But if it relies on probabilities:
Probability is the branch of mathematics concerning numerical descriptions of how likely an event is to occur, or how likely it is that a proposition is true. The probability of an event is a number between 0 and 1, where, roughly speaking, 0 indicates impossibility of the event and 1 indicates certainty.
Then if we went back in time and started from scratch at image two, it's not certain that the probabilities would turn out exactly as the did before, if the probability of something happening is for instance 0.65, it would mean that it wouldn't be 100% certain. It's important to point out that this is on a subatomic level. So it wouldn't interfere with our abilities to for instance predict ahead of time, like us being able to predict that in 3 days Earth will be in certain position.
But where it could be interesting is in regards to determinism which say...:
Determinism, in philosophy, theory that all events, including moral choices, are completely determined by previously existing causes. ... The theory holds that the universe is utterly rational because complete knowledge of any given situation assures that unerring knowledge of its future is also possible.
Even though this might be true for quantum mechanic as well, it wouldn't be true in the very moment where we have to determine the state of these subatomic particles as I see it, because of this probability factor it could have gone whatever way. And therefore it appears to be determined, as if there were only one way it could ever have gone, which is the very one we experience obviously. But again rewind several images and run it again, and our experience of the Universe being determined is exactly as we would feel now, despite that it might be completely different, because none of the probabilities ended up as they were before.
Our mind or the decisions we make are not made out of the blue for no reason, but are based on former events, current situations, estimates, experiences, instincts etc. For instance, you making a choice to run over the street, could be made because a car is coming at you at high speed, so you make an estimate of the current situation that, if you don't hurry up it will hit you. But was it determined that you should be in that spot at that very moment or not, so you could make that exact decision? If everything was determining before hand going all the way back to the beginning of the universe, surely that seems to be the case and you actually had no choice in the matter at all, but given that there is no guarantee that going forward in time again would result in the same thing. Is it then truly determined or is it just an illusion of there being only one option?
Im not sure we can tell the difference and therefore not sure if free will is determined either depending on how you look at it. But I do think that most people live with the impression that we do have free will with restrictions, whether it is an illusion or not.
Again I can't stress enough that I don't know a lot about these things or quantum mechanics etc. That I might very well be completely wrong about everything written here, due to my lack of knowledge