Evolution is a science, and thus deals only in what can be known. It restricts itself to empirical facts and consistent, logical theories about the world derived from those facts. It is not a philosophy, nor a belief system, nor a religion; nevertheless, it does touch upon matters which, to some people, fall under the scope of those things. Creationists have seized upon this inevitable confusion and used it to defend themselves against the undeniable proof that creationism is religion and not science by claiming that evolution is a religion as well. However, as will be shown, this claim is completely false.
There are some specific qualifications that are usually required for a religion, and evolution fails all of them. It has no prophets. It has no scriptures. It has no temples and no priesthood. It sets no rules for behavior; evolution does not promise me a reward if I adhere to it, nor does it threaten me with punishment if I deny it. It provides nothing to worship; no one prays to evolution. It is silent on the topics of life after death or the existence of the soul. It says nothing about the existence of a god or lack thereof – it can be seamlessly incorporated into any belief system, from the most ardent atheism to all but the most literal fundamentalist theism, with any deity or other supernatural entity of choice given credit for using evolution as the mechanism by which life was caused to diversify. And most importantly, evolution is a science and does not require religious faith of any sort.
Of course, some creationists would dispute some of the above claims. Some would no doubt make the claim that evolution does have both a prophet and scriptures – Charles Darwin and his book On the Origin of Species. However, this claim is ridiculous on its face. While Darwin was an intelligent and perceptive scientist, no one has ever claimed that his writings were divine revelations, nor that he possessed any special perception or faculty not available to the rest of humanity. His central insight of natural selection was born of much education, study and meticulous observation. In principle, anyone could have come up with it (and someone else did – English naturalist Alfred Russell Wallace proposed the idea independently, at nearly the same time). Nor is it claimed that Darwin’s writings are inerrant – much the opposite, in fact. It is widely recognized that his work, though amazingly insightful and indisputably correct in most places, was wrong or incomplete in several areas, such as his speculations on the mechanism of inheritance, which were only poorly understood in his day and which he could not have been expected to know the truth about. While evolution does incorporate many of Darwin’s original ideas, it has also changed and grown beyond him. His principle of natural selection has been merged with the more recent sciences of genetics and molecular biology to form the present-day theory of evolution known as the modern synthesis.
Other creationists might also make the claim that there is a penalty for opposing evolution – censure, ridicule and exile from the scientific mainstream, with corresponding denial of job offers and tenure. However, the history of science shows that this claim is mistaken. There are many now-successful ideas that were first considered wrong or unlikely, such as plate tectonics, symbiosis as the origin of mitochondria and chloroplasts, or the hypothesis that ulcers are caused by bacteria and not by stress. But the advocates of these ideas were not excluded from the scientific community. Instead, they continued to collect evidence and publish papers, and when their arguments were sufficiently well-supported, many scientists accepted these ideas and they became part of the scientific mainstream, often winning their authors glory, fame and recognition. That the creationists have not been able to do likewise – either because their ideas were so easily debunked that they could not survive peer review, or more commonly, because they made no attempt to even participate in the process – is not proof of inherent bias in science, but the griping of sore losers. If at any future time they want to present new evidence and participate, they are more than welcome to do so.
But none of these are the main reasons why creationists wrongly insist that evolution is a religion. There are two of these.
The first is the claim, made by countless creationists, that evolution is inherently atheistic, or that it denies the existence of God. However, this is not true. It is true that evolution stands in opposition to a narrowly literal reading of a small portion of a particular religion’s scripture, but this is a far cry from the sweeping accusations made by its detractors. Contradicting one possible interpretation of one chapter of one holy book is hardly the same as denying the very possibility of God’s existence.
The fact is that evolution, like all scientific theories, is naturalistic; that is to say, it confines itself to what can be empirically measured, tested and explained. All supernatural phenomena – God, angels, devils, miracles, and so on – are non-naturalistic and thus fall beyond the scope of science. Evolution does not say God exists; neither does it say God does not exist. Such a question simply cannot be considered by science. It is, instead, one for theology or philosophy. What evolution does do is provide a consistent scientific explanation for the development of life that does not require direct divine intervention – it does not require miracles, but neither does it forbid them. If there is a God, evolution tells us how he caused life to develop and diversify. If there is no God, evolution tells us how life developed and diversified in his absence. But the theory itself does not say either of these things; it merely says what happened, making no metaphysical claims one way or the other. If evolution is atheistic because it does not require miracles, then so is all the rest of science.
Additionally, in rebuttal to the creationists’ accusations of atheism, one could make the very relevant point that the majority of the world’s religious people find no conflict between evolution and their faith. As recently as 1996, the Pope, the spiritual leader of one billion Christians around the world, reaffirmed that there was “no opposition” between evolution and the Bible. A great number of other religious organizations accept the truth of evolution as well; some of them are listed in the “Voices for Evolution” section of the National Center for Science Education‘s site. Finally, there is the Clergy Letter Project, which has gathered over 10,000 signatures from Christian clergy of various denominations affirming that evolution does not conflict with religious belief.
To name the most obvious example, there was once a time when a straightforwardly literal reading of the Bible led people to the conclusion that the Sun orbited the Earth. This conclusion was not only taken as following naturally from the plain meaning of the text, it was held that to doubt it was to deny that the Bible had any meaning at all. As Cardinal Bellarmine wrote in 1615 about Galileo’s heliocentric theory, “But to want to affirm … that the earth is situated in the third sphere and revolves with great speed around the sun, is a very dangerous thing, not only by irritating all the philosophers and scholastic theologians, but also by injuring our holy faith and rendering the Holy Scriptures false.” The similarities to the creationists’ arguments against theistic evolution are instructive. To deny geocentrism, the church authorities said, was to deny that the Bible was inspired by God and free of error; to admit heliocentrism would bring Christianity crashing down. Yet today, heliocentrism is universally acknowledged, even among creationist groups (though there are a few holdouts ), and Christianity has not come to an end. In fact, most people are wondering why anyone ever thought there was a conflict in the first place. The reader is invited to find parallels with the current debate over evolution.
The second major reason creationists often label evolution a religion is this. To believe in evolution takes faith, they say, because no one has ever seen it happen. They argue that to accept evolution requires a leap of faith that is at least as great as the leap of faith required to accept God!
Leave aside for the moment the question of what this says about the creationists’ views on religion. (Surely they approve of it? Why do they think calling evolution a religion is an attack on it? As some have noted, it’s as if they’re saying, “Hey, you guys are just as irrational as we are!”) The fact remains that this accusation, like all the others, is untrue. Evolution is a science, and as such, it is based on and accepted by empirical evidence – not faith.
By definition, faith is belief in something for which there is no objective evidence. In the case of evolution, nothing could be further from the truth. Evolution is one of the best-supported theories in all of science, upheld by numerous lines of evidence from many different fields that all converge on the same conclusion. For instance, there are many transitional series showing the large-scale change of life over time, and nested hierarchies of genetic similarity that corroborate these fossils and allow us to chart the tree of evolutionary relationships. Nor is our evidence of evolution limited to reconstructing what happened in the past. Indeed, we can directly observe all the components of evolution working around us today – genetic mutations, increased or decreased by drift and acted upon by selection, to produce new genes and new morphology conferring differential reproductive success and increased fitness on a wide range of living organisms. No faith is necessary, because acceptance of evolution does not require one to accept any process that cannot be observed today and that is not supported by evidence to prove its occurrence in the past. The creationist claim that evolution requires faith in unobserved processes is flatly false.
To accept evolution, or any scientific theory, it is absolutely unnecessary to make a leap of faith – it wouldn’t be a scientific theory otherwise. All that is required is a willingness to accept evidence, conclusions drawn from that evidence, and theories logically based on those conclusions. Unlike the fundamentalist religion of creationism, evolution can be freely questioned, scrutinized in detail and refined to fit the evidence, and indeed, even its most dedicated defenders are constantly doing this. Just like general relativity, the heliocentric solar system, or the germ theory of disease, the theory of evolution can be taken on the basis of the evidence alone. It is not accepted or rejected by, and does not depend on, people’s faith.
 See, for example, what the Institute for Creation Research has to say about theistic evolution here (sample: “There is no harmonizing or fence-straddling here; one must make a choice between holding to theistic evolution or believing the plain statements in the Bible”). Answers in Genesis says similar things here.
 Robert Bellarmine: Letter on Galileo’s Theories, 1615. http://www.fordham.edu/halsall/mod/1615bellarmine-letter.html.
 For an example of one such, see The Earth Is Not Moving.