I think it’s more complicated than free will existing or not.

If you knew every single possible value about the universe at its start and had a perfectly accurate model of physics, you could theoretically predict/simulate everything that would ever happen. For practical reasons, though, that’s impossible, even ignoring weird quantum effects, for the simple reason that that is a lot of data points, more than any of us could reasonably keep track of- it’s like how, in sufficiently controlled conditions, a fair dice can roll the exact same number 100% of the time, but there are enough variables that are hard enough to control for in a normal situation that it’s basically random.

Similarly, if you knew everything about every human on Earth, you could theoretically predict exactly what any of them would do at any given moment. Of course, that’s just not practical- the body and brain are a machine that is constantly taking in input and adapting to it, so in order to perfectly predict someone’s thoughts and actions, you’d need to know every single detail of every single thing that has ever happened to them, no matter how small. Then, you’d need to account for the fact that they’re interacting with hundreds of other people, who are also constantly changing and adapting. It’s just not possible to predict or control a person for any reasonable length of time like that, because one tiny interaction could throw off the entire model.

Just look at current work with AI- our modern machine learning algorithms are much more well-understood and are trained in much more contained environments than any human mind, and yet we still need to manually reign them in and sift through the data to prevent them from going off the rails.

So, technically, I suppose free will doesn’t exist. For practical purposes, though, what we have is indistinguishable from free will, so there’s not much point getting riled up about it.

I have the feeling most people cling to free will as a concept because not having free will raises questions if a “self” truly exists. However the existence of free will can be as scary if not more, since how could we define a “self” if it could freely do something not based on what defines it.

Hard determinist here. It doesn’t make the future predictable by me, but I don’t see how randomness could really occur. And then likewise there’s no such thing as free will.

Quantum mechanics are probabilistic, which serves as a good argument for the universe as a whole being probabilistic. The position of a single particle could change a great many things!

Here is a good lecture from Robert Sapolsky on Human behavioral biology that will replace your question with more questions:
https://www.youtube.com/watch?v=NNnIGh9g6fA

Also, specifically addressing your spoiler,

You react to choices the specific way you do because of experiences you’ve had previously.

Reverse time without changing anything, you’ll always make the same choices because you’re having the same thoughts each time every time, because you’ve been conditioned the way you are.

The universe doesn’t “know” where it’s going, but the plan is already in action. You can choose whatever you want to do, but if you were the same person in the same circumstance, you would and will always make the same decision.

Free will is way too vague of a concept, that it’s probably not worth pursuing the answer.

I’m fairly certain free will does not exist. There’s really no solid evidence for it, and no credible scientific mechanic by which it could operate.

Quantum physics provides strong evidence that the future is not deterministic, though it can produce deterministic-like results in larger systems.

The concept of belief is rooted in free will, is it not?

Well, first things first, it is not a “simple” philosophical question. The best minds of humanity have been tackling this problem since forever, and there is still no definitive answer yet.

Ironically, for all the religions since the dawn of time, some kind of evidence for free will has emerged from the frontiers of science. Quantum mechanics, for instance, is based on the fact that at the subatomic level, nothing is known for sure. Therefore, the “initial conditions” issue is no longer true.

Someone with a greater intellect than mine once stated that the quantum nondeterminism underlying the functioning of the human brain could be the key to freeing it from the conundrum of cause and effect. In other words, yes, we have free will. Suggested readings: “The Elegant Universe” by Brian Greene, “Gödel, Escher, Bach: An Eternal Golden Braid” by Douglas Hofstadter, “The Book of Job” in the Bible.

Just my 2¢…

Quantum mechanics shows the universe really does just operate on probabilities. On the smallest scales we can probe we see that the universe is non-deterministic. But average out those probabilities 10^20 times for a coin and everything may look pre-determined to our macroscopic lives.

The question is underspecified. Why do you want to know if free will exists? What will you do differently if it does exist vs if it does not exist?

This is similar to questions like, “is water wet?” You can generate endless debate on the topic, but it’s all intellectual masturbation until you are genuinely looking for the answer to a specific question.

To be deterministic there should be someone or something what determine it, as an agnostic i don’t believe neither at 100% just a 50/50, we should prove first if there is something out there or not who/what determine or not things.

I’d say free will exists. Sure, you are shaped by your environment, your genetics and so on, but in the end you can still decide what you want to do. In theory I could simply quit my job tomorrow, wander off into the sunset and then drown in the next ocean. Or as someone brought up criminals, you could stab someone just trying to disprove the universe is being deterministic.

If you know every single atom in this moment and had unlimited computing power, you’d probably be fantastic at telling the weather. Or if you map every neuron in someone’s brain you might know what they are about to do next. But at this point you are just looking at the present data and can maybe calculate the next few seconds (but not even that is 100% sure, just a very good guess).

The question is how far forward would you be able to look just based on current and past data? A minute? A day? A month? At that point the whole thing breaks apart in my opinion. It’s like looking at the stock market where you have tons of past data and think you can predict the future simply based on that.

There’s so many complex sources of randomness, the most likely solution is that things are just that, random. And you can decide what you want to do with your own life, at least until you die (or don’t, who knows what the future brings). Honestly the whole question is dumb, there is no single being that knows everything, so it really doesn’t matter. In the grand scheme of things even humanity is just a tiny blip on the timeline and we’re with very high probability not unique. Just based on numbers there is a high chance other life forms have existed before us, might exist right now with us (somewhere else in the universe I mean, there’s also plenty on Earth) and will exist in the future.