Predictability and the Lack of Free Will
You are going to read the next word: Hello.
I predicted that you would read that word, and you did. So how much control did you really have over reading that?
Now you might say that you were just curious, and you could well have chosen not to read the word. Okay. But imagine if I told you that tomorrow at 1:24:26 PM you are going to read the word Harbor on a computer screen. That's probably not going to be true for you, but what if it actually happened? You would start questioning just how much of your future is pre-set. The more I can predict your future correctly, the more I'm showing you that your future is set, and thus predictable.
The more information I have, the more predictive power I'll have. If I had your schedule for tomorrow, I could tell you where you'll be at any time. If I'd witnessed all of your thoughts in the past few months, I could tell what your schedule for tomorrow is without even looking at it. If I knew exactly how your brain works and exactly what sensory inputs you've received since being conceived, I could tell you what your thoughts have been and how your brain works. And if I knew how your brain works and what your schedule is for tomorrow, I could predict with a good amount of accuracy what the day after would look like as well. And if I wanted more accuracy, I'd just have to know all the sensory inputs you'll be receiving tomorrow, which again is just a matter of knowing everything about everything from before that. And if I knew everything that has happened in the physical world and in everyone's mind right until this moment, I can predict exactly what will happen the next, the one after, and so on.
If your decisions are predictable based on your mental processes and your sensory inputs, and your mental processes are knowable based on your parents' genes and all of your experiences, and your sensory inputs are predictable based on the state of everything around you and their history, then I can always predict what your next decision will be, how it will affect things, and how the effect will affect things and so on.
And if I had all the information until yesterday, I could've told you what you would be doing today. But perhaps if I'd told you, you'd try to rebel and act a different way, just to show that you have control over your actions and their effects. But if I knew that you had a rebellious tendency and enough energy to exercise it, I could've predicted that as well.
And if I knew everything until the day before yesterday, I could've predicted everything until yesterday, and so on back.
So on back until the very initial stage of things -- before any life existed at all. There is no doubt that before any life form, there was no sentience and therefore no possibility of free will either. So if you knew the exact position and momentum of every single particle right before the first life form, you could predict that a certain blob of molecules somewhere in the universe would, in the next moment, become what we would call "alive".
So if you knew the exact position and momentum of everything right before the first life form became alive, or even better, right at the very start (call it the big bang or whatever), you could know exactly what would be happening for all of the future. And if you can know what the future is, then everything is already decided and there can be no change in it, even if someone wills it. So there is no such thing as free will.