I had this roommate once. One evening, being somewhat drunk from her lack of sleep -- so, slunk -- she sat on the floor of the kitchen and wouldn't leave until I agreed that there was a fundamental difference between having free will and our choices being theoretically predictable. More specifically, she was struggling with Leibniz' idea that if the laws of physics are deterministic as they appear to be at a certain scale (as they were known to be until the early twentieth century), then if we had a computer big enough and enough knowledge about the positions and the velocities of all particles in the universe, then we'd be able to predict the outcome of anything, even of the human mind, of every decision each one of us will ever make. In my naive attempt to ease her distress, I explained to her that making a big computer means one thing: to take a physical system and make it do the same as the original system whose behavior you wanted to predict. For example, taking a complicated system of wires and transistors which we call a computer, use its dynamics to simulate the motion of a falling brick by showing a dot on a screen that moves like the brick would move. And we do this in the interest of skipping forward and figuring out the result for different masses, different shapes without spending too much time and money. But of course, we often neglect that this process is extremely inefficient. After all, all it takes for reality to perform that motion is a brick, whereas we need to precisely set up an immensely complicated machine with millions of intricate pieces of electronics. And that is only to simulate a simple motion. You haven't even come close to replicating what's going on inside the brick, how each atom is moving. You'd need a much bigger computer for that. So let's think about this in a simpler way. To keep track of what you're doing you divide the atoms in the universe in two sets: set number 1 is the universe you want to simulate and set number two is the physical system you use to simulate set number 1. The more detail you want in your simulation of 1 the more atoms you must add to 2. But there is only a finite number of atoms in the universe! Eventually, you will have moved so many atoms from 1 to 2 that you end up with a really big computer (1) to simulate a really simple universe (2). In other words, if you want to simulate the universe, you need a computer at least as big as the universe. You can use a system to simulate something faster, but at the cost of making everything else much more complicated. Ultimately, nature is the most efficient computer of itself.
Coming back to my stubborn roommate, whom I like very much, my point was that such a computer cannot exist and therefore the issue was not an issue. In fact, it doesn't even really matter if you're free or not, what matters is that you can experience in a very real way the consequences of your actions, independently of whether someone can build a computer to simulate your choice. But she wouldn't give up. She insisted there was a difference, despite the fact that there wasn't any physical, rational difference. She got caught up in this swirl of her own thoughts, not being able to choose between two propositions that both seemed equally possible but felt very different. And stuck along with her there are hundreds of other people and a whole, very proud, realm of human academia: philosophy, where its practitioners continuously argue with each other and with themselves about issues which they can't resolve or, at best, can only resolve by the strength of their status and by the natural tendencies of the human culture of their time.
Philosophers fail to address in a practical way the fact that two thoughts can have exactly the same physical consequences and yet feel very different, that they can be logically equivalent but somehow one feels reasonable while the other one is completely outrageous. They face the problem in the same way they address anything in their lives: they talk about it. They ramble and ramble on, hoping that at every turn of their train of thought they might have missed an exit that could distinguish the two thoughts and finally justify rationally why one seems so appealing and the other one so wrong. But the problem with it is that there is nothing wrong with the train of thought, the issue lies in the inconsistency between the rules of verbal thinking and of emotional thinking (for a simple psychological experiment, either read this or listen to this). The two reach different conclusions on the same matter, frankly, very often, because you've carefully used your verbal abilities to reach a conclusion, while you let your emotional queue daydream at random.
The problem with most philosophical questions is that they are really just twirls where these two ways of thinking disagree. The only way to come out of it, is to use a different method. Rational thinking must be paused because it has already reached a collection of satisfactory conclusions, of stable structures. The tool to go on must be emotional thinking, which means to do with your emotions what you did with your thoughts: combine them, generate new ones, and so on until a stable state is reached. Then you can harmonize the rational and the emotional. Of course, this is difficult at first and takes a lot of practice to learn how to do it properly. But the effort is no greater than the effort it once took you to learn how to think with your mind's voice, how to think with words and numbers and logical statements. The next time you find yourself chasing after your own tail, think outside the box. Or rather, think inside the box, just in another part of it.
