Greta Christina in AlterNet:
When you look at the history of what we know about the world, you see a noticeable pattern. Natural explanations of things have been replacing supernatural explanations of them. Like a steamroller. Why the Sun rises and sets. Where thunder and lightning come from. Why people get sick. Why people look like their parents. How the complexity of life came into being. I could go on and on.
All these things were once explained by religion. But as we understood the world better, and learned to observe it more carefully, the explanations based on religion were replaced by ones based on physical cause and effect. Consistently. Thoroughly. Like a steamroller. The number of times that a supernatural explanation of a phenomenon has been replaced by a natural explanation? Thousands upon thousands upon thousands.
Now. The number of times that a natural explanation of a phenomenon has been replaced by a supernatural one? The number of times humankind has said, “We used to think (X) was caused by physical cause and effect, but now we understand that it's caused by God, or spirits, or demons, or the soul”?
Exactly zero.
More here.