In recent years a few religious scientists have claimed a refutation of the main tenets of Darwinian evolution that does not rely on biblical authority or the biblical young-Earth account of creation. This refutation purports only to show that an “intelligent design” rather than the unguided processes of random variation and natural selection that Darwin postulated must be responsible for creating life and human beings. The thesis has quickly gained enormous attention and notoriety. Several states have considered requiring teachers to describe the intelligent design theory as an available alternative to standard evolutionary theory in public high school biology classes. A Pennsylvania school board adopted that requirement a few years ago, and though a federal judge then struck the proposal down as an unconstitutional imposition of Christian doctrine in public schools,1 other public bodies in other states are still pursuing similar programs. President Bush recently appeared to endorse these campaigns: he said that “I felt like both sides ought to be properly taught.”2 The Senate majority leader, Bill Frist, who is said to covet the Republican nomination for the presidency in 2008, agreed. He said that teaching intelligent design theory along with evolution, as competing scientific explanations of the creation of human life, was fair because it “doesn’t force any particular theory on anyone.”3

If there is any scientific evidence against evolution, then of course students should be taught what it is. But the intelligent design movement has discovered no such scientific evidence at all. We must distinguish the following three claims. (1) Scientists have not yet shown to all their satisfaction how the Darwinian processes of random mutation and natural selection explain every feature of the development of plant and animal life on our planet; some features remain areas of speculation and controversy among them. (2) There is now good scientific evidence that these features cannot be explained within the general Darwinian structure; a successful explanation will therefore require abandoning that structure altogether. (3) This evidence also at least suggests that an intelligent designer created life and designed the processes of development that have produced human beings.

The first of these claims is both correct and unsurprising. The details of evolutionary theory, like the phenomena it tries to explain, are enormously complex. Eminent biologists disagree in heated arguments about, for example, whether some features of developed life are best explained as accidents or byproducts of no survival value in themselves. Evolutionary biologists face other challenges and disagree in how best to meet them.

The second of the three claims is false. It does not follow from the fact that evolutionary scientists have not yet found or agreed on a solution to some puzzle that their methods have been shown to be defective, any more than it follows from historical controversies or unproved mathematical conjectures that the methods of historians or mathematicians must be abandoned. Scientists have so far found no reason to doubt that the evolutionary puzzles can be solved within the general apparatus of…