In a little over three weeks, on July 10, it will be exactly 80 years since John Scopes went on trial, charged with teaching evolution as briefly set forth in "A Civic Biology Presented in Problems" by George W. Hunter.

Echoes of this notorious "monkey trial" continue to resound: A school board in Georgia tries to put stickers on biology textbooks advising that evolution is "a theory, not a fact." A Pennsylvania school district wants science teachers to inform students that "intelligent design" is an alternative to Darwinian theory, a notion gaining support in at least 20 states, with Kansas in the lead. These publicized disputes, furthermore, are only the tip of an iceberg of passive resistance, by many school boards and teachers who want to avoid controversy, to teaching evolution at all.

Opponents of such resistance can scarcely contain their exasperation. Why won't this conflict just go away? Why must the American Civil Liberties Union, which recruited Scopes so long ago to challenge Tennessee's anti-evolution statute, still be at it? How can it be that almost half the population rejects the idea that humans have evolved, and almost two-thirds want some form of creationism taught in public school science classes?

Michael Ruse has an answer. A professor of philosophy at Florida State University, he is, by his own account, "an ardent Darwinian," who testified for the A.C.L.U. in its successful challenge to a creationist law in Arkansas.

In "The Evolution-Creation Struggle" (Harvard, 2005), Professor Ruse takes a long look at why opponents of evolution feel so threatened and why evolutionists are so surprised and perplexed at the opposition.

"The full story," he writes, "is far more complex than any of us, including (especially) us evolutionists, have realized." In his view, evolutionary thought and the strand of Christianity that rallied to oppose it were two "rival religious responses" to an existing crisis of faith stemming from the rationalism of the Enlightenment and its 19th-century sequel.

Although Darwin's own work was a model of professional science, a great deal of evolutionary thought before and after him, in Professor Ruse's judgment, deserves to be termed evolutionism, a kind of secular religion built around an ideology of progress.

That ideology was not necessarily wrong, but it threw evolutionary theory into one of the two camps increasingly dividing Christians: the liberal postmillennialists, who believed that the building of Christ's rule on earth was already under way, and the conservative premillennialists, eagerly anticipating Christ's Second Coming.

Casting the evolution-creation struggle into the framework of the postmillennial-premillennial struggle does not always make for a tidy fit. But one point becomes indisputable. From the beginning, evolutionary theory has been drenched in religion. The aggressors in the warfare between theology and science were not just religious believers insisting that their ancient Scriptures were the basis of scientific truths but scientific enthusiasts insisting that evolutionary theory was the basis for conclusions about religion.

Many of the latter were of course what Professor Ruse calls proponents of evolutionism and pseudoscience. (The biology text at the center of the Scopes trial, along with useful advice about diet and regular bowel movements, reflected eugenics, then fashionable, in warning that allowing the birth of "parasites" like the mentally and physically handicapped would be "criminal.") But as Professor Ruse notes, as genuine science no less than as pseudoscience, "Darwinian evolutionary theory does impinge on religious thinking."

The challenge to literal readings of the creation stories in Genesis is the least of it. Other elements of Darwinism go right to the heart of any belief in a caring, almighty God.

The power of strictly natural interactions of random events and reproductive advantage over huge spans of time to explain the emergence of diverse and complex life forms appears to render the guiding role of such a God superfluous. The grim picture of those life forms, including humanity, emerging through a ruthlessly cruel process of natural competition appears to render such a God implausible.

The vigorous arguments made by Darwinians like Richard Dawkins and Daniel C. Dennett to the effect that contemporary evolutionary theory has buried all traditional religious beliefs may not be conclusive, but they cannot be dismissed, nor rebutted simply by the fact that some evolutionists continue to be believers.

Then there is the debate about the "methodological naturalism" that for purposes of scientific investigation restricts explanations to findings about material nature. Does "methodological naturalism" lead inexorably to a "metaphysical naturalism" holding that material nature is in fact the whole of reality?

Professor Ruse says no. But he acknowledges that the slippery slope is there. And "though many evolutionists may themselves be willing to make the slide," he writes, "they should not be surprised when others, seeing a slippery slope from methodological naturalism to metaphysical naturalism, stop themselves at the top of the hill."

In the end, Professor Ruse's new book suggests that the religious resistance to evolutionary theory is a lot more understandable and a lot less unreasonable than its opponents recognize. The neat formula "evolutionary biology is evolutionary biology, religion is religion, and the former belongs in public schools but the latter does not" cannot do justice to the fuzzy reality of the evolution-religion hybrid.

Professor Ruse does not offer an alternative formula or delve into the church-state questions raised by proposals to include creationist or intelligent-design ideas in school curriculums. He entertains hope that Christian and atheistic evolutionists can unite in defense of the "huge overlap" in their scientific positions and in their commitment to a "postmillennial philosophy" of human progress.

But his ultimate appeal is for greater modesty and self-awareness.

"Those of us who love science," he writes, "must do more than simply restate our positions or criticize the opposition. We must understand our own assumptions and, equally, find out why others have (often) legitimate concerns. This is not a plea for weak-kneed compromise but a more informed and self-aware approach to the issue."
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Michael P.