What better question can there be for the New Statesman to tackle in its God issue than that of God's very existence?

"I'm a believer", published in last week's New Statesman, deals with that very topic. The way that I prepared it was by asking 30 prominent people to tell me their main reason for believing in God. For most of them, this was the Christian God. To add some spice to the mix, half of them were scientists.

I was intrigued to know how their answers would differ from the others'. Many of the answers are set out in full or in part in my article. But what I'll try to do here is delve behind the quotes.

Although most people were able to supply objective reasons for their belief, some of them conceded that their decision to believe nevertheless required them to take a leap of faith. This seems to be what the Bishop of London meant when he echoed an Alfred Tennyson refrain, saying that there is everything suggestive which constantly draws him "to cleave ever to the sunnier side of doubt".

Similarly, the Daily Mail columnist Peter Hitchens told me that he is "ceaselessly interested to know why anyone would – in the absence of definitive proof either way – actively prefer the idea that the universe is accidental and without purpose. Such a position seems to me to be far more intellectually difficult than mine." Perhaps he partly had in mind his brother, Christopher, one of the world's most prominent atheists, who also prides himself on being an "anti-theist": that is, someone who is firmly opposed to God.

A quarter of those I asked told me that they had experienced God. Usually this was in the form of what they believed were answered prayers, as well as feeling the presence of Jesus in their lives. Perhaps surprisingly, this answer was more common among the scientists. Even so, it was a former cabinet minister, Jonathan Aitken, whose experience was the starkest. As he told me, "Some years ago I went through an all-too-well-publicised drama of defeat, disgrace, divorce, bankruptcy and jail. In the course of that saga I discovered a loving God who answers prayers, forgives and redeems."

"All that you imagine"

Believers and unbelievers differ in the probative value of their religious experience. Perhaps a sceptic is hardly entitled to dismiss a personal experience that he has not had. Then again, most Christians would surely agree that the experiences of followers of other religions cannot amount to proof of the existence of their gods. So, is it just Christian experience that is to have any evidential value?

Among the non-scientists, the most common argument for God's existence was the example set by Jesus. For the radio and TV presenter Jeremy Vine, "The story of the gospels has stood the test of time, and Christ comes across as a totally captivating figure." Similarly, the anti-abortionist Lord (David) Alton referred to God's genius and love, which he said are expressed most powerfully in the claims of Christ. And the Bishop of Liverpool added, "All that you imagine God would be, Jesus is."

Denis Alexander, director of the Faraday Institute for Science and Religion, developed this point. He said he was "intellectually persuaded by the historical life, teaching, death and resurrection of Jesus of Nazareth, that He is indeed the one He claimed to be, the Son of God. Jesus is most readily explicable by understanding Him as the Son of God."

An advantage of believing in God for this reason is that a believer does not have to answer the usual follow-on question: but if there's a God, why would it necessarily be the Christian God? Even so, many sceptics would counter that the nearest to a contemporary record of Jesus's life is the Gospel of Mark, which was written at least 40 years after the crucifixion. So, perhaps unsurprisingly, scholars have had trouble with the historicity of several features of the gospel accounts.

Richard Swinburne, probably the world's best-known living theologian, told me that there are cogent arguments for the existence of God. One of his reasons was the most common one I heard, particularly because most of the scientists mentioned it. For instance, Dr Hugh Ross, who leads the American Christian apologetics ministry Reasons to Believe, told me that it was discoveries in astronomy that first alerted him to God's existence.

He referred me to what he called compelling evidence for God's existence emerging from research into the origin of the universe. In particular, the Big Bang appeared to him to offer the best explanation for the history of the universe and was consistent with biblical teaching.

The government's "poverty tsar", Frank Field MP, succinctly made the same point when he said that believing in God makes more sense than any other explanation of why we are here.

Predictive text

A similar argument that sometimes crops up when people discuss God's existence is that if the laws of physics were even slightly different from how they are, life as we know it would be impossible. It is claimed that as it is highly improbable that the fine-tuning of the laws of physics arose by chance, God must be responsible for it. A third of the scientists brought up this point.

On a related theme, the prominent American biologist Kenneth R Miller asked me: "Why should science, which requires order and predictability to work, even be possible? Where does that order come from?" His answer is God.

It is largely for these reasons that the bestselling science writer Professor Paul Davies considers that the universe is rationally ordered. However he told me, "I am sure I don't believe in any sort of God with which most readers of your article would identify."

Sceptics may be surprised that so many people, including well-known scientists, feel the need to posit a God to explain either the Big Bang or the laws of science. After all, last year Stephen Hawking made headlines when his latest book concluded that God was not needed to kick-start the Big Bang because the universe was able to create itself from nothing.

Hawking's opinion was based on M-Theory, which predicts that there is more than one universe; rather, the number of universes in existence is in the region of ten followed by 500 zeros. So it is hardly surprising that we find ourselves living in the universe whose laws of physics allow us to exist. However, not all physicists feel comfortable with M-Theory, especially because it is not yet complete.

About a quarter of those questioned saw the Bible as presenting a convincing case for God. Stephen Green, national director of Christian Voice, believes that there is an intellectual coherence to Scripture. And Hugh Ross told me that the Bible predicted what scientists would later discover: the beginning of space and time, the continual expansion of the universe, the constancy of physical laws and the concept of entropy.

Perhaps a queue of sceptics wishing to challenge this bold way of interpreting the Bible would stretch across that very expanding universe. And even the main events of the Old Testament, such as the exodus of the Israelites from Egypt and their subsequent wandering in the wilderness, have been doubted by archaeological studies.

A third of the scientists considered that humanity provided evidence of God's handiwork. Michael Behe is the biologist whose theory of irreducible complexity forms the purported scientific basis of Intelligent Design. He believes that the fact that humans can comprehend and reason indicates the existence of God. The molecular biologist Nick Brewin also commented that humanity appears to occupy a unique position among all life on earth due to its Godlike ability to store and manipulate information.

He argued that, rather than concluding that this was all mere chance, we should try to make sense of the signs and wonders that are embedded in a revealed religion.

Even so, there was a consensus that science cannot explain everything. Professor Michael Reiss, professor of science education at the Institute of Education, London, stated that his belief in God does not involve abandoning the scientific way. "Instead it's a larger way of understanding our relationship with the rest of the world, our position in nature and all those standard questions to do with why we are here, whether there is life after death and so on."

A fifth of everyone I questioned saw the existence of God as simply the best explanation going. As Stephen Clark, professor of philosophy at Liverpool University, put it concisely: "I believe in God because the alternatives are worse."

The same number of people referred to the existence of morality and our notions of beauty as pointing to God's existence. According to the physicist Peter Bussey, it is reasonable to suppose that our shared sense of beauty and morality should correspond to some kind of transcendent source. "Why else should it be there?" he asks.

Sceptics may reply that our sense of right and wrong is simply a product of human evolution; after all, societies founded on poor moral systems are likely to die out. Even so, the question of whether Darwinism alone can explain adequately why morality should pass through the generations is a hotly debated topic within the context of the God Debate.

Nowadays, Christians may feel that they are under siege by the so-called New Atheists and are having to justify their beliefs as never before. But whether they like it or not, this is a debate that will go on and on.

Andrew Zak Williams has written for the Humanist and Skeptic. To contact the author email: andrewbelief@gmail.com.