I just finished reading Stephen Jay Gould's Rocks of Ages, an ambitious little book in which Gould (an agnostic and a leading evolutionary biologist) tries to lay out an explanation of the appropriate domains of science and religion.
Gould's thesis is that Religion and Science represent separate but equal fields of knowledge which never truly come into conflict because they deal with different issues. He calls his schema NOMA (short for Non-Overlapping Magisteria) and basis the division on the old line that "science tells us how the heavens go, while religion tells us how to get to heaven."
Why does an agnostic scientist tackle this particular topic? Partly out of an honest desire to clear up what Gould sees as a common misunderstanding. Regardless of how others may view his work as a vocal defender of the modern evolutionary synthesis in biology, Gould did not consider himself an enemy of religion. He writes in the introduction about how religion has always fascinated him, partly because he felt that it was a major gap in his upbringing -- his parents having abandoned their Jewish faith to embrace militant atheism. Gould says he believes his parents went to far -- despite the fact that he himself remains an agnostic, he feels that his parents had an irrational hatred of religion (and notes that atheism is as much an act of faith as theism.)
There are some very good things that Gould has to say, and which Christians should be glad to hear someone on the 'other side' acknowledging. Gould makes it clear that no one lives without holding religious beliefs and making religious judgments. He contends that moral/ethical decisions are invariably based upon a form of religious belief, whether that belief is based upon revelation, instinct, or philosophical introspection. In that sense, an atheist relies just as much upon religion as does an orthodox Jew, it is simply that the atheist's religious beliefs are different (that there is no God) and so his conclusions also are different from those of a believer.
Gould clearly lays out the argument that judgments of worth (good, justice, beauty) and moral norms (killing is wrong, charity is good) cannot be the result of 'scientific' thought. Even the most secular person, he says, invariably makes many important decisions about his life based upon religious thought. To this extent, he's saying the same thing as many Christian apologists. We should be glad to hear it coming from him as well.
While questions of ethics and purpose are the domain of religion in Gould's schema, the domain of science is to determine the history and workings of the physical world. So (after first acknowledging that many of Galileo's problems were of his own making) Gould points to the Galileo case as an example of religious authorities violating NOMA by asserting that the Earth must be stationary with the Sun orbiting around it. Gould says it would be a violation of the realm of science for religious authorities to assert that certain things about the world 'must be' regardless of what the evidence suggests. For instance, while generally praising Humani Generis for it's treatment of the evolution question, he raises an eyebrow at the assertion that Catholics must hold that all current humans are descended from a specific man and woman. Gould says he doesn't know enough about Catholic theology to know if this is meant in a primarily theological way, but that if Pius XII was speaking in biological terms, this constitutes a violation of the separation between the magisteria of science and religion. Religion, in his schema, may define what humans should do and what they are in a metaphysical sense, but it cannot say "we know it for a fact that all humans are descended from a specific couple at some point in history".
Here I think Gould's outsider's attempt to address the proper domain of religion falls a bit short. He doesn't seem to understand the relationship between statements about what the world means and what we ought to do in it and more physical or historical statements about the world. Many moral norms are based upon an understanding of what the essence of some thing or action is. For instance, the Church's teaching against birth control is based on the understanding that the marital act is in its essence fertile -- regardless of whether the particular case of marital intercourse at hand is physically likely to result in conception. Thus, the Church does make a statement about physical reality in proclaiming this doctrine. If it were somehow proved totally false that sex had anything to do with reproduction, the Church's prohibition of birth control would be rendered foolish.
The other weak point in Gould's thinking (and certainly an understandable one given where he is coming from) is that he seems to imagine a very simple dichotomy between 'natural' and 'miracle'. Thus, he takes it as a first principle for scientific thinking (and for his division between science and religion) that no major elements of the physical development or workings of the universe are the result of 'miraculous intervention'. Thus, he cites Newton for violating NOMA when he suggested that God might reach in and correct the planets in their paths every so often just to keep them on track.
The Newton example is an easy target, because Newton seems to have thought in the same way as Gould: either something is 'natural' or 'God did it'. It seems to me that a better understanding would be to recognize that if God is (as we believe he is) all powerful, omnipotent, and our creator, that His 'interventions' would be very different from the way that I might reach into a model trail rig and nudge something that wasn't going the way I wanted. In the Catholic tradition we believe that the universe is actively held in existence by God's will. The workings of the universe are, thus, in a certain sense, inside the mind of God. What we see as natural laws are not something outside of God which work along in their merry way until God intervenes. Rather, natural laws are what we are able to see of the rational mind of God as expressed in the workings of His creation. Natural laws remain fixed because God is fixed. Thus, the reason that science can proceed with a certain confidence that the planets will not go off track and need to be nudged back into position through a miracle is that the laws of physics which control the movement of the planets are already themselves an expression of God's will for how matter should work and interact.
Incidentally, it's within this perspective that it seems to me wrongheaded to insist that there must somewhere be scientifically detectable signs of God's 'design' where He reached in and helped something reach a form that mere laws of nature could not have achieved. God created and maintains the laws of nature. They're not some lesser thing that he occasionally infuses strokes of brilliance into. Nor is a rock or a pool of water any less 'designed' because of its simplicity than the most complex features of the human body. God's stamp is upon it all equally, not just the cool bits.