“There are all sorts of reasons for believing in God, and here I’ll mention only one. It is this. Supposing there was no intelligence behind the universe, no creative mind. In that case nobody designed my brain for the purpose of thinking. It is merely that when the atoms inside my skull happen for physical or chemical reasons to arrange themselves in a certain way, this gives me, as a bye-product, the sensation I call thought. But if so, how can I trust my own thinking to be true? It’s like upsetting a milk-jug and hoping that the way the splash arranges itself will give you a map of London. But if I can;t trust my own thinking, of course I can’t trust the argument leading to atheism, and therefore have no reason to be an atheist, or anything else. Unless I believe in God, I can’t believe in thought; so I can never use thought to disbelieve God.”
~ CS Lewis, The Case for Christanity
It is my experience that atheists usually are afraid of the manipulative aspect of God. They are afraid that they are no in control in anything, that everything has been set-up ahead of time by a malevolent god. Their freedom has been taken away, and they will be judged not by their own actions, but on the way things have been manipulated by an outside force.
AS Lewis points out, though, the idea of evolution alludes to other forces of manipulation. What if your body was just made up of competing organisms that were using you make sure they survived? Your brain, your eyes, your liver, your toe, they are evolved things that somehow found their way to each other, and are no working together to survive. Your thoughts are not your own but are the will of these organisms, and sometimes they rebel, forcing you to do things that you otherwise wouldn’t have done?
But how would you know that you would or would not do something? Your thoughts since the womb have been clearly to satiate these organisms. You would never have been free to begin with. You can’t trust your thoughts, or anybody else’s.
So, splash out those maps of London, you free thinkers! I’ll stick to the map given us.