In making their case, the atheists often appeal to the revolutionary influence of Charles Darwin. In his book The Blind Watchmaker, Dawkins writes that “Darwin made it possible to be an intellectually fulfilled atheist.” He points out that the universe and its creatures show irrefutable evidence of design. Before Darwin, there was no plausible explanation for that design other than to posit a designer. So atheists had no way to account for life’s diversity and complexity. Many—including skeptic David Hume—were forced to concede that each creature was fitted with the equipment needed for its survival by some sort of higher being.

The great achievement of Darwin’s theory of evolution and natural selection, Dawkins and others say, is that it shows how creatures that appear to be designed have in fact evolved according to the pressures of chance and survival. Atheists now have an alternative explanation for why fish have gills, why birds have wings, and why human beings have brains and arms and lungs. Indeed, in the atheist view, evolution refutes the biblical account of human creation, exposing it as a crude and primitive myth. Carl Sagan remarks that “as science advances, there seems to be less and less for God to do…. Whatever it is we cannot explain lately is attributed to God…. And then after a while, we explain it, and so that’s no longer God’s realm.’ This is none other than the God of the Gaps, who is forced by science into ever greater irrelevance. Dawkins argues that contrary to the claims of religion, we humans “are survival machines—robot vehicles blindly programmed to preserve the selfish molecules known as genes.”

In his book Darwin’s Dangerous Idea, Dennett contends that Darwin’s theories are a kind of “universal acid” that “eats through just about every traditional concept, and leaves in its wake a revolutionized worldview” about the nature of man and the universe. Specifically, Dennett and others interpret Darwinism to mean that all life can be understood entirely in natural and material terms. Man is nothing more than matter in motion. The soul? A product of fantasy. The afterlife? A myth. Human purpose? An illusion.