“Occam’s razor” is a philosophical position, attributed to medieval theologian William of Occam (Ockham). It is that the simplest explanation that fits all of the facts is the one that should be accepted. He applied it to theology, but it works in all areas of study. It is one of the foundational assumptions of science.
Religious people have, for the past few centuries, abandoned William of Occam’s theological premise. The reason is that science has steadily put physical explanations of nature in place of spiritual ones. At first it was that the Earth goes around the Sun. Then it was the idea that gravity and momentum, not angels, propelled the planets in their orbits. A few simple Newtonian equations explained as much as a multitude of angels.
One of the biggest examples of a simple natural explanation replacing a complex theological story is, of course, evolution. At the time of William Paley, every species was seen as not only a special creation by God but as evidence that God was good. Even mosquitoes. Evolution replaced “natural theology” largely because one, single explanation—natural selection—replaced thousands of separate acts of design and creation. Why does each species exist? In Paley’s time, each species had its own reason. Ever since Darwin, there has been only one reason: evolution.
But evolution is far from being the only example. If I were a fundamentalist, I would be a lot more worried about psychology than about evolution. Scientists have now explained nearly everything that happens in our “minds” and “hearts” as a physical or chemical process that occurs within our brains. This applies even to the most intense religious experiences (see the earlier essay about the Near Death experience.) Now, we know that these processes, involving neurons, neurotransmitters, hormones, and genes occur. In order to believe that a person has a spirit that thinks and feels, you have to believe that this spirit exactly mirrors, in every detail, the functions of the brain. You have to create, without evidence, an imaginary shadow of the brain. Occam’s razor says that, if the brain explains everything, there is no need to invent a spirit that is just a duplicate of the brain.
Occam’s razor, a philosophical position invented by a theologian, has now turned against theology.