Charles Darwin is clearly the Copernicus of the modern era. No other scientist (not Einstein or Crick) and no other thinker (not Marx or Freud) comes close to the lasting impact that Darwin has had on our sense of ourselves and our place in the world. At the same time, like many other great scientists before him, Darwin admitted that he had very few original ideas. He was more of a synthesizer, one who brought together the ideas of others and the insights of several centuries into a unified field theory of life: a testable, repeatable set of observable hypotheses which have stood the test of two centuries. Darwin’s ideas and their applications are now virtually transforming our daily lives and the lives of countless living things around us. Think genetically modified food. Think artificial intelligence. Think cloning.

Keith Thomson’s superb book is primarily about the thinkers who came before Darwin, those scientists, clerics, and philosophers who struggled to make sense of the complexities of “Nature” as nature came to be more clearly understood. Did God make the fossils if fossils meant that most of what God had made had failed? Did African people and Chinese people and Native American people all descend from Adam and Eve: how did that work? Did Jesus look like a Caucasian rock star? Did God want us to change the world he made and the natural laws that govern that world, or did he want us to leave what he made alone? Scholars and laypeople alike are still very interested in these questions, since we are currently arguing about them from our lecterns, our pulpits, our laboratory benches, and sometimes even from the presidential podium.

As Thomson reminds us, the Scottish philosopher David Hume literally emptied the churches of England with two simple questions. If we can believe in any being that we cannot see (a dragon, an alien, a God), then surely it is just as easy not to believe in that being? Similarly, miracles in every religious tradition — Christian, Buddhist, or Hindu — resolve themselves into a simple question: is it more likely that the laws of nature (hitherto so absolute and eternal) have been suspended for an instant, or is it more likely that one human being has told a lie? In Hume’s view, the Christian God could not have existed when the Egyptians were worshipping only Ra, or the Greeks were worshipping only Zeus, since all of these monotheistic deities are mental constructs, just as all of the polytheistic gods were. For Hume, Lazarus was resuscitated by a supremely wise doctor and teacher, just as we now resuscitate dying people simply by breathing into their lungs, in countless hospitals every day, whatever religion we practice or do not practice.

More important than logical skepticism to Thomson’s analysis of interactions between science and religion is the way churchmen, scientists and intellectuals have sought — always unsuccessfully — to show that the world described in sacred writ might be the world described by Galileo, Isaac Newton, and by natural historians going all the way back to the Greeks. Nature is full of mistakes and failures; maybe God just put them there to test our faith. True faith can never be doubted, but the objects of true faith (God, an afterlife, miracles) can never be proven. Bishop Ussher claimed that our world had been created on Sunday, Oct. 23, 4004 B.C., but by 1850, many people had a hard time agreeing with him.

The founder of marine science, Henry Gosse, was also an evangelical who argued that Adam and Eve had navels, since we all have navels and we are all created in “God’s image.” Gosse soon became a laughing stock in Victorian Oxford and London. More subtle and sophisticated were thinkers like William Paley and Robert Chambers. Paley argued that the wisdom of God was revealed consistently throughout creation (“natural theology”), and the other of whom argued, well before Tennyson, that nature was relentlessly red in tooth and claw: death, disease, and decay were as central to our world as flowers, sunsets, and puppies (“agnostic materialism”).

The only problem with Thomson’s wonderfully readable book is its American subtitle: “Reconciling God with Nature.” The word “reconciling” makes it seem as though the volume shows that God was successfully linked to nature by pre-Darwinian writers. Of course, this curious subtitle may have been written by an American editor. In fact, the key to Thomson’s argument is quite clear by the end of the book: talk about God is one thing; talk about science is another thing. However much these separate discourses try to engage one another, the twain can never really meet: not in Darwin’s day, not in ours. The technical problem is what philosophers call a category mistake  — do not ever talk to your spouse using the language you use to talk to your tax accountant.

Thomson finally shows his own well-argued hand in a cryptic last paragraph in which he admits that, since the days of Paley, Lamarck and Erasmus Darwin, “Religion and science have not been able to agree upon the reformulation of a set of questions that they can attack jointly.”

The argument of Before Darwin is powerful precisely because Thomson is unwilling to accept an easy, squishy solution to his own central question. Science must be empirically verifiable. It must be testable, repeatable and agreed upon by people of different faiths and different worldviews. Religion is none of these things. When the cure to cancer or AIDS is finally announced, it will not matter if the scientist who has developed it is Jewish, Methodist, Hindu or an atheist. The cure that makes people get well will still be the cure.

The title of the earlier British edition of Thomson’s book is The Watch on the Heath: Science and Religion Before Darwin. That title gets closer to the book’s central message. The watchmaker behind the watch of nature is only an article of faith; talk about God can never be the subject of scientific investigation. Modern science, in fact, tells us that the watch on the heath does not need a personal maker any more than each snowflake needs a personal, willful maker. All the snowflake needs is the impersonal and deterministic laws of gravity, freezing, and crystalline structure — the laws of nature, as John Locke might have said.

Take this book with you to church, the chemistry lab or the public school. In all of these settings it will remind you that science is about one way of describing the world and religion is about another. In the modern world, as Thomson hints, we are gaining a clear sense of which side is winning the debate.