What about free will?
If atheism is true and everything is based on cause and effect then how can there be free will? For there to be free will there has to be a soul that isn’t based on natural actions.
Free will is an extremely difficult concept, in part because it is so hard to define. Generally, people will say that free will is the ability to make choices that are not determined by prior causes (or by an act of God, but I see no need to go there). But I’d say that, in practice, such definitions are really much vaguer than they appear.
If free will exists, then there must be a non-deterministic mechanism by which decisions are made. We’ll call this the soul. How would the soul make decisions? Its decisions aren’t random, so they much be the result of some non-random process. But how can there be a non-random process without cause and effect? If the soul is pure thought (whatever that might be), it still makes decisions based on various inputs and preferences, and it may well be that the same decision would always be arrived at given the same inputs and preferences. If the soul were truly able to make decisions without cause and effect, then I would assume that it could make completely random decisions if it so desired, and humans show a marked inability to do that.
Let’s look at this from another direction. Free will is, in a nutshell, the ability to act unpredictably. You would rather cross a bridge than jump off of it, but if you have free will you could jump off the bridge. Or could you? Do you really think it’s possible that you might decide to jump off a bridge for no reason whatsoever? If not, then the phrase “I could jump off the bridge” stops being helpful in the search for free will. What you are really saying is, “If I had a reason to, I could jump off this bridge.” But if you have a reason to jump off the bridge — even if it’s a dump reason — then you are making a decision under different circumstances than when you made the decision to cross the bridge.
In a nutshell, saying “I feel like crossing this bridge now, but if the situation were different I would jump off it” isn’t much an expression of free will.
So what do I think free will is?
At this point, I don’t think we know enough about how the human mind works to do more than make educated guesses. However, we do know many relevant facts:
1) We are self aware, but we are not completely self aware. That is, we do not have complete knowledge of our own workings (you can’t sense your glands working, for example).
2) Decision making is at least in part related to the brain. Damage to the brain can impact the decision-making process.
3) Human decision making is flawed. There are a number of documented “cognitive illusions” — mistakes in reasoning that pretty much everyone makes.
4) We may not be conscious of all of our motivations.
5) We are not in control of all of our actions. Even voluntary actions can become reflexes over time.
6) People sometimes lose control.
None of these make me confident that we are in any position to judge whether or not free will exists, and none of them seem to point toward a soul or any other non-material decision-making part of humanity.
But does it feel like we have free will? It sure does, but that doesn’t mean anything. Our ability to sense some of our own thoughts — our self awareness — gives us the ability to accomplish great things. But the fact that we are self aware does not imply that we know anything about how our mind works. For all we know, if we built a computer that had the power of a human brain it might think it was self aware and had free will even though — in theory, at least — we could sit down and calculate all of its decisions ahead of time.
Similarly, it’s possible that if there were a thousand duplicate universes you would make all the same decisions in every one of those universes, and in every one of those universes you’d think that you had free will because you could have chosen differently.
So, in a nutshell, if you want to prove something supernatural exists based on humans having free will, you’re going to have to define free will rigorously and prove that it exists first.