I've long been active in the battle over the teaching of evolution in public schools. One of the arguments that we hear quite often is the "Fairness Argument". It goes like this: There are two explanations for the existence of life on earth, either life evolved by "random chance" (evolution) or it was put here by a creator (creationism or "intelligent design theory"); since neither has been "proven", it's only fair that if you're going to teach one, you should teach them both and let the kids decide. To the average person, this argument sounds eminently reasonable. Who, after all, could argue against "fairness"? And what's so bad about presenting both "theories" and letting kids decide for themselves? But the reality is that this argument, while sounding persuasive on the surface, falls apart on analysis.
The first flaw in the argument is a logical fallacy known as a "false dichotomy". A false dichotomy is an argument that sets up two alleged opposites and implies that they are the only two possibilities. In this case, the argument is wrong both because the two sides of the dichotomy are not opposites at all, and because they are not the only two possible explanations. Let's take them in order....
Are evolution and creation opposing explanations for life on earth?
The answer is "sometimes", but not necessarily. That is, evolution cannot be reconciled with some specific creation stories, or at least with literal interpretations of those stories, but it does not, in any way, address the question of the existence of God. A great many people believe that evolution is an inherently atheistic idea, but that is simply false. Science does not allow for supernatural explanations because they cannot be tested or falsified in any way, but that doesn't mean that scientific theories end with "and therefore, there is no God." Evolution is no more "atheistic" than the kinetic theory of gasses or the theory of relativity. If you believe that God created all life on earth a few thousand years ago, then evolutionary theory, and the vast amount of data that supports it, cannot be reconciled with that explanation. But this creation story, which is typically referred to as Young Earth Creationism (YEC), is limited only to the most literal interpretation of the book of the Bible. That is an interpretation that is not shared by Catholics or most of the mainline Protestant denominations. I have been priveleged in my work in this area to cross paths with a few brilliant Christian scientists like Howard Van Till, Steve Schimmrich, Glenn Morton and Keith Miller. They along with like-minded colleagues such as Ken Miller, Terry Gray and Davis Young, would tell you that the work they do as geologists, molecular biologists and chemists, rather than being a negation of their religious views, is motivated by their faith, and that their faith is both informed and deepened by their work as scientists. The conflict is only with those who insist on the most literal reading of Genesis 1.
What are the other possibilities?
The other flaw in the false dichotomy is that even if one were to accept that they are necessarily opposed to each other, they're not the only two possibilities. As my friend Rob Pennock points out in his wonderful book Tower of Babel, there are lots of religious or quasi-religious alternatives to evolutionary theory. You not only have the creationism of fundamentalist Christianity to deal with, you also have the Muslim creationism of Harun Yahya. You have the Hindu/Vedic creationism of Michael Cremo and Richard Thompson that says that humans have been on the earth for hundreds of millions of years and that the natural history of the earth is cyclical as it says in the Hindu scriptures.. And you have the Raelians, who argue that humans were bioengineered by aliens. Indeed, the Raelians issued a press release pledging their support for the Intelligent Design movement's attempts to open up the classrooms so that their explanation could get in there too. And surely if it's "only fair" to allow one religious alternative into the classroom, then it's "only fair" to let them all in. The result, of course, will be nothing but confusion and a watering down of the science education curriculum in public schools.
Let's also remember that the precedent, once set, does not end with evolution. Evolution is not the only scientific idea that conflicts with some particular interpretation of a religious text. Heliocentrism is the theory that the earth revolves around the sun, which conflicts with geocentrism, the idea that the earth is fixed at the center of the universe and everything revolves around the earth. It may sound silly, but there is a growing movement in Calvinist Christian circles in support of geocentrism, led by the astrophysicist Gerardus Bouw. For many, in fact, anti-evolution and anti-heliocentricity arguments go hand in hand, as both rely on a literal reading of bible verses. The geocentrist site at fixedearth.com bills itself as the "non-moving earth and anti-evolution web page." Heliocentricity is every bit an affront to geocentrists as evolution is to creationists. If it's only fair to allow creationism in as an alternative in biology classes, then it's only fair to allow geocentricity in as an alternative in earth science classes.
For that matter, you have the flat earthers. Contrary to common perception, the Flat Earth Society is serious in their claims. They truly believe that the earth is flat. My late friend Bob Schadewald, the chronicler of so many fringe scientific movements, got to know and befriended Charles Johnson, the now-deceased head of this group. They are very serious in their beliefs, and they are based almost entirely on their interpretation of the bible. If it's only fair to allow in creationism and geocentrism, then it's only fair to allow the flat earthers to have their views represented as well.
The list could go on and on. For hundreds of years it was believed that sickness and infirmity was sent by God as punishment for our sins. This is clearly an alternative to the germ theory of disease and the fairness argument surely applies as well in that case. Pat Robertson and other fundamentalists have often been heard to claim that natural disasters like hurricanes and earthquakes are God's punishment for our sinful culture (I have often joked that the 700 Club should include a weather forecast based on this theory - "Sodomy is up 14% in the midwest this week. Expect clouds of locusts"). The fairness argument requires that we present this as an alternative to conventional meteorology and seismology. For that matter, why limit the fairness argument to science? Surely the holocaust deniers should be allowed their say in our history classes. Why not "present both theories" and "let the students decide for themselves"?
Clearly, the answer to this is that science classes should teach science. Evolution is accepted nearly universally in the relevant fields of science not because it denies God (which it doesn't) but because it is the central unifying theory in a dozen different disciplines. Nothing makes sense in biology, paleontology, comparative anatomy, zoology, genetics, or several other fields without evolution to explain the data. There is simply no other model that can match the explanatory power of evolution over such a vast range of evidence. The YEC alternative fails miserably to explain even the most basic facts of our natural history, while vague ideas like Intelligent Design Theory (IDT) don't present any testable model at all. Rather than weakening our biology curriculum to allow in fanciful religious alternatives, we should be strengthening it.