Lets say that free will it is a mathematical function in your brain, f(X), which is decision you make and X is an array of input.
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Of course we call it a free will, if we go from the idea that this function unrestricted and gives you best possible solution. But in reality f(X) will always be restricted by the environment. The first and foremost restriction is an input X. No matter how we try our decisions will always depend on information we get to initiate decision making. Other people trying to manipulate us to do something by giving us only that input information which supposed to lead us to "right" decision. Even nature does that.
But here is an interesting thought, how would this function work if it was absolutely unrestricted? Basically how does absolute Free Will looks like?
It is impossible to see, but we can try to imagine it at least. Lets assume that we have spherical person in vacuum. It is an ideal person in ideal environment, where f(X) cannot be restricted at all. In other words absolute Free Will. But there's comes another moment, f(X) cannot work without X, input. In real world your decisions are predictable, limited and not as free as you may think because you have limited information about any particular event, about which you have to make a decision. So returning to our ideal person in vacuum, for it we have to have an ideal input, X should become an array of all possible information, which allows you to make unrestricted, absolute free, ideal and unbiased decision.
The question is how would it look like? You have spherical person in vacuum with absolute free will and all possible information in the world. What kind of answer you can get?
And, funny enough, whatever question you ask to that kind of person in that situation the answer will be always the same: Absolutely random. This is another non existing matter, there is no such thing as absolute randomness. Even though there is such thing as random generator, they will never give you ideal random answer, because they always influenced by environment. How? Because no matter how you try your "random" answer will always depend on initial input that random generator function gets, which cannot be absolutely random.
So basically, what we coming to is that f(X) is indistinguishable from random generator function given the ideal circumstances. And the only reason we think that our free will is not random is because our input is limited, which allows us to make a weighted decision. But more information we have more random our decisions are.
This whole idea is not purely philosophical, it is widely used in computer science these days, know as heuristic algorithms.