In the first in a series on the big science questions, Julia Hinde looks at science's relationship with religion while, below, John Polkinghorne argues that the study of physics need not preclude a belief in the Almighty.

"I am unaware of any irreconcilable conflict between scientific knowledge about evolution and the idea of a creator God," says Francis Collins, the man behind the US human genome programme. "I am a geneticist, yet I believe in God."

Collins is not alone. Over the past few decades, many acclaimed scientists have declared their belief in God and science. They include Sir John Houghton, co-chair of the scientists' working group of the Intergovernmental Panel on Climate Change; John Polkinghorne, former president of Queen's College, Cambridge, and a particle-physicist-turned-Anglican-priest; Carl Feit, immunologist at Yeshiva University in New York and a Talmudic scholar; and Russell Stannard, a physics professor at the Open University and a reader in the Church of England.

Such views are not universally held. Richard Dawkins, Oxford University's professor of the public understanding of science, and a vocal atheist, is quick to dismiss religious belief. He has called anyone advocating a creator God "scientifically illiterate", while terming religion "a virus". Others see religion and science as different paradigms, both legitimate but unrelated.

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Yet some 3,000 years after a single creator God was first mooted, in an age when science is seeking to understand and control man's genetic make-up, and when powerful telescopes allow us to look to the very heart of the "big bang", the notion of God persists. It is a notion that sells popular-science books, exercises theists and atheists alike, and is as riven with division today as ever.

Belief in a single, perfectly good creator of the universe can probably be traced to ancient Israel, about 1,000BC, says Richard Swinburne, Oxford University's professor of the philosophy of Christian religion. Almost every society about which we have knowledge appears to have had faith in some divine force. People, it seems, have always looked to the divine for answers to questions that found no explanation in their society.

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From the outset, there have been challenges. But according to David Wilkinson, an astrophysicist-turned-minister and a fellow in Christian apologetics at St John's College, Durham University, questions about the existence, rather than the nature, of a creator have largely been a feature of more modern debate.

Until the mid-19th century, science and religion went, for the most part, hand in hand in western society. Scientists typically explained their motivation in religious terms and many leading scientists were clergy. Even the church's persecution of Galileo, one of the most regularly cited examples of conflict between science and religion, did not involve his denial of the existence of God, though it did throw into question man's place at the centre of the universe.

The scientific revolution of the 17th century - with its development of instrumentation, including microscopes - allowed scientists to marvel at the wonders of nature and hence God. According to Wilkinson, design theory - the idea that nature is so well designed and so beautiful that it cannot be so by chance, but must be the work of God - can be traced back to Greek literature, but its "flourishing came with the scientific revolution".

By the 18th century, there was opposition between some scientists and religion, and by the early 19th century, the idea that the natural world was a simple mirror of God's work was under attack. It was Charles Darwin's On the Origin of Species, published in 1859, that presented, for some, the ultimate challenge to a creator God. Darwin undermined several traditional arguments for belief in God, including design theory and the unique status of humans.

Darwin at one time intended to join the clergy and was mindful not to use science to attack religion. Even at the time, some in the church were open to his ideas, able to incorporate his work into their beliefs. But several scientists were less accommodating. Thomas Huxley's legendary debate with the bishop of Oxford in 1860 pitted evolutionary science firmly against belief in God. Two books of the time, William Draper's 1874 History of the Conflict Between Religion and Science and Andrew Dickson White's 1896 History of the Warfare of Science With Theology in Christendom , were instrumental in creating a confrontational image that endures today.

According to John Brooke, professor of science and religion at Oxford University, the post-Darwin period was not a simple conflict between science and religion, but it did spark moves to professionalise and secularise science, separating the discipline and its practitioners - who until the 1850s had been required to be devout Christians - from theology.

By the early 20th century, a large number of scientists no longer believed in God. A 1916 survey of US scientists found 60 per cent did not believe in or doubted God, a figure that the author predicted would increase with the spread of education. But despite this and significant progress in scientific understanding, particularly in the fields of genetics and quantum theory, which some believe obviate the need for a creator God, a survey in 1996 found 40 per cent of US scientists believed in God.

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But in a time when man has the power to play with life itself, how can there still be room for God? The fact that the universe exhibits just the right conditions to foster life is one pointer, says the pro-God corner. "Recent scientific work on the fine-tuning of the universe has shown that the initial matter and the laws of nature have to have very special features if organisms are to evolve," Swinburne says. The fact that our universe has just the right features might be chance or an indicator of the existence of a very large number of universes. Or it could be divine influence.

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The existence of fundamental laws about the behaviour of matter is also mooted as evidence of the divine. "This is quite extraordinary," Swinburne says. "I believe God has a reason. By matter behaving this way, it is not only beautiful, but allows finite beings like us to make a difference to the world and each other."

Others cite human cognitive abilities, which greatly exceed the demands imposed by evolutionary pressures, and science's inability to completely account for the origin of life. Though most scientists back ideas of biological evolution, there is less consensus on how natural selection began.

Collins, director of the National Human Genome Research Institute at the National Institutes of Health in the United States, describes himself as a "theistic evolutionist". "If God decided to create humans who he could have a relationship with, why should he not use the mechanism of evolution to do this? It's an elegant idea," he says.

That no scientific proof for the existence of God has been forthcoming does not deter these theists who also include the scriptures and the wealth of human religious experiences as reasons for their belief. Moreover, they argue, science might not be able to detect something as subtle as God.

Others go further. Michael Behe, a biochemist at Lehigh University in the US, says God's handiwork can be seen in "irreducibly complex" parts of organisms that could not have evolved from simpler components. His arguments for intelligent design have been attacked by many scientists, particularly in the US where scientific creationism - which takes a literal view of the biblical creation story - is still a major force.

Other scientists, including the Harvard paleontologist Stephen J. Gould, view science and religion as two different realms, logically distinct and fully separate in styles of inquiry and goals. He argues that science asks objective "how" questions, while religion asks "why". Gould emphasises the need for the individual to use both to build a rich view of life. "Science and religion should be equal, mutually respecting partners, each the master of its own domain with each domain vital to human life in a different way," he says.

Those with less faith in the divine argue that the space for God is shrinking. Rather than accommodating science and God, they believe science to be the only reliable path to knowledge. Dawkins perceives irreconcilable differences between science and religion. Championing Darwinian evolution, he sees this alone as sufficient explanation for the diversity of life. And his view of a universe without design or purpose dismisses those who seek answers to "why we are here" questions.

Nobel prizewinning physicist Steven Weinberg agrees: "The more the universe seems comprehensible, the more it seems pointless." He argues that the prevalence of evil and misery proves there are no signs of a benevolent designer.

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