One of the things that contributed a lot to my eventual deconversion to atheism was learning more about how the human brain works. Many believers will admit that they may not have a rational basis for what they believe, but they know it’s real just the same and I accept those statements as sincere. The reason that I don’t find them convincing, however, is because it’s possible to experience all sorts of things that feel entirely real even when we know for a fact that they are not. It’s possible, for example, to still gain some benefit from a placebo even when you know it’s a placebo.
These days there are all sorts of cool experiments being done that show that the brain can be tricked into thinking something that’s not real is very real even when the evidence that it’s not real is right there in front of its eyes. Experiments like the rubber hand illusion:
The rubber hand illusion is more than a vaguely creepy parlor trick. It’s a window into relationship between our mental and physical self-conception.
During the illusion, a participant’s hand is hidden, and a rubber hand positioned so that it appears as her own. She knows that it’s fake—but when both hands are stroked simultaneously, what’s seen and felt becomes blurred.
Suddenly the rubber hand literally feels like it belongs to her. Consciously she knows it’s not true, but that doesn’t matter. Threaten the fake hand, and people under the illusion’s spell respond as if their own hands were threatened.
Scientists have now shown that the hidden hand’s temperature drops during the illusion: its effects aren’t simply mental, but physical as well, and could even hint at as-yet-unknown processes of disease.
The fact that they can clearly see the hand is fake and not a part of their body doesn’t stop these people from feeling as though it were and reacting accordingly. Their brain overrides what is plain to their eyes and insists that the fake hand is real and something to be protected. Knowing this it becomes very easy to see how people can have experiences that couldn’t possibly have occurred that seem very real to them and which they find very hard to dismiss as a result. Be those experiences sensations of communion with God(s), abductions by aliens, or what have you.
Posted on 08/28/2008 at 03:26 PM 
I get into arguments about this with people all the time. If you think you’ve seen an alien spacecraft, don’t believe it. Make what you see convince you that it can’t be anything else. 99% of people who are convinced they’ve seen aliens have reached a point where the first four or five things that it could have been they’ve discarded for purely trivial reasons and say “What else could it be?“ Well, I don’t know… that’s why it’s called a “UFO”. Your eyes can make your brain add details to your environment that aren’t there.
And if you already want to believe, you very often won’t have done any critical thinking in the first place. If you’re forced to believe, then you might be getting somewhere.
Religious experiences are even worse, because they rely on something you “feel” without any extra data to consider. Atheists and religious folk probably have all the same “strange” experiences. The difference is; when you are already pre-disposed to believing, you most likely will be convinced. The Atheist will say “That’s odd” and go on with life, whereas for the Christian, it was “obviously” God touching them. It sounds like a no-brainer: “You CAN be fooled with your eyes wide open”, but people will completely disregard that little fact when it comes to relating these kinds of stories to others.
Besides, if our brains didn’t work this way, magic shows would hold no appeal. Everyone knows that it’s a trick, and most people probably already know how most of these tricks are done and are watching for it, but good magicians continue to fool us by being good at what they do.