I (personally) believe free will is a pseudo-problem, that the argument about if free will exists or not depends totally on how you define it, and depending on the definition it either straightforwardly does or does not exist. There are a few different popular, contradictory, definitions, and arguing from these different definitions is the most common way I see two people disagree on whether or not free will either obviously does or does not exist. The question then becomes, what definition of free will makes the most sense, what properties does it have, and why is it better than the others?
"You say: I am not free. But I have raised and lowered my arm. Everyone understands that this illogical answer is an irrefutable proof of freedom."
Free will, I think, obviously exists, which is why everyone talks about free will as if it exists, makes decisions as if free will exists, and why people generally find arguments that free will does not exist either shocking, or unintuitive. To start, I believe that there is no fundamental "true" underlying definition of a word, two people can say the same thing, "free will", and be trying to communicate two totally different concepts. There's nothing wrong with this, but it means that you need to try and figure out what people are talking about exactly before you decide if you disagree or not. For example, this anon is obviously correct.
>>316373 if you define free will as the will totally lacking constraints, any whatsoever, then free will does not exists. In this definition, as long as you can prove the will is limited in some way, any way at all (this is easy), you have a perfect proof for free will not existing. I don't think this definition of free will makes sense, however. Nobody who is arguing that they have free will, and that free will exists, believes that they can fly, give themselves a million dollars, etc. So, the people who disagree are clearly using another definition.
The other definition of free will that leads you to free will not existing is a free will which requires you have access to all of the inputs to your decision making. What is being talked about in this post
>>316372 is the ability to do a probabilistic (but not perfect, this will be important later) sort of precognition by measuring someone's brain as they make decisions. You can see the brain leaning towards a choice before the person making the choice has "settled" on that decision. However, it's generally already accepted that consciousness is essentially running on the brain, which is a substrate that it has no access to or control of. You are undeniably influenced by this substrate, which in turn acts to steer your will. However, do people consider jump scares to be proof that there is no free will? You certainly did not decide to become scared. Emotions in general are not something you have control over, people do not decide to become happy, sad, or to fall in love. None of these are though, in my opinion, proof of free will. This simply shows that the brain is another external factor which influences the will, and influences on the will are generally already accepted. For example, gravity prevents you from flying, and so is an external influence on the will that narrows the set of choices you can make.
This leads us to the major main set of arguments against free will, determinism versus compatibilism. I'm a strong compatibilist, and I believe that the most reasonable definition of free will that best describes what people talk about when they talk about free will, and the definition that applies most directly to what we actually experience, requires determinism.
Will requires determinism. What "you" are is fundamentally, "will" your will, your discrimination between choices, is what makes you an individual, and not someone else. You can separate two different people on their unique will. For example, if time were to be rolled back, and you were to be born again, and then time was restarted, your life would play out exactly as it has, down to the tiniest most minute detail (for this thought experiment, we're ignoring quantum mechanics. Imagine every wave function collapses to the same state once again). This is because you are "you", not someone else. Specifically, there is no external oracle, there is not separate device, which does not perfectly emulate you so exactly as to actually be you yourself, that can perfectly predict your actions. This is what the "will" is. Imagine how insane, how absolutely unreasonable the world would be if there was simply a cloud of possibilities winging through space, where the same inputs could lead to totally different results, where as you were writing a post, watching anime, doing anything at all what you were exeperiencing was in fact just cosmic noise, that you didn't think anything, believe anything, or do anything that you could call your own and say was different from other people. That, if your position swapped with someone else, you could not somehow discriminate between the two and say which was you. If, in fact, you could perfectly duplicate yourself, and that copy ended up making different decisions, how could you say that "you" exist? What would be the self? So then, determinism is in fact required for will to exist at all, and will is required for any useful definition of free will.
Now, how can will be free? It's obvious, as I've already said, that this doesn't mean unlimited choices. If you want to use this definition of freedom, then free will does not exist. It also doesn't mean uninfluenced will. This is a subset of limitations on choices, since anything that cuts down your number of choices is an "influence", but I think it's reasonable to say that putting on a coat when you go out because it's cold outside is not a proof that you are unfree because your will is being shaped by external factors outside your control. I don't think, then, that it's too big of a step to include the body as an external factor. Is eating when you're hungry proof that you are unfree? It seems to me that it's fine to categorize it as just another external factor. So, what then, is free, if there are all these influences and limitations on your self? The thing that is free, is the will. Your ability to weigh these options, after all of the external limitations and pressures that shape them and give those options certain qualitions, your ability to decide between the options and choose which limitations and pressures make a certain option more desireable than another, is what is free. There is no external force, nothing outside of the self which is manipulating the will so that the weights it places on choices are changed. Different people value being hungry at different weights and choose differently. Different people value love at different weights and choose differently. You and I make very different decisions, you and I place different weights on different choices, because you and I are not the same. It is this process, the will itself, that is free.
With either a different definition of freedom, or a different definition of will, then free will exists or does not exists based on these arguments, but this is the definition that I think is clearest and most reasonable.