After four centuries of breathtaking scientific progress, many wonder why intelligent people would still feel the need to believe in God. Andrew Zak Williams decided to find out. Over the course of several months, he corresponded with dozens of scientists and other public figures, quizzing them on the reasons for their faith. Here is a selection of the responses.

Cherie Blair, barrister

It's been a journey from my upbringing to an understanding of something that my head cannot explain but my heart knows to be true.

Jeremy Vine, broadcaster

There is a subjective reason and an objective reason. The subjective reason is that I find consolation in my faith. The objective reason is that the story of the gospels has stood the test of time and Christ comes across as a totally captivating figure.

In moments of weariness or cynicism, I tell myself I only believe because my parents did; and the Christian faith poses more questions than it answers.

But I still return to believing, as if that is more natural than not doing so.

Richard Swinburne, emeritus professor of philosophy, University of Oxford

To suppose that there is a God explains why there is a physical universe at all; why there are the scientific laws there are; why animals and then human beings have evolved; why human beings have the opportunity to mould their character and those of their fellow humans for good or ill and to change the environment in which we live; why we have the well-authenticated account of Christ's life, death and resurrection; why throughout the centuries millions of people (other than ourselves) have had the apparent experience of being in touch with and guided by God; and so much else.

In fact, the hypothesis of the existence of God makes sense of the whole of our experience and it does so better than any other explanation that can be put forward, and that is the grounds for believing it to be true.

Peter Hitchens, journalist

I believe in God because I choose to do so. I believe in the Christian faith because I prefer to do so. The existence of God offers an explanation of many of the mysteries of the universe - es­pecially "Why is there something rather than nothing?" and the questions which follow from that. It requires our lives to have a purpose, and our actions to be measurable against a higher standard than their immediate, observable effect. Having chosen belief in a God over unbelief, I find the Christian gospels more per­suasive and the Christian moral system more powerful than any other religious belief.

I was, it is true, brought up as a Christian, but ceased to be one for many years. When I returned to belief I could have chosen any, but did not.

Jonathan Aitken, former politician

I believe in God because I have searched for Him and found Him in the crucible of brokenness. 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.

James Jones, Bishop of Liverpool

One word: Jesus. All that you imagine God would be, He is. His life and His love are compelling, His wisdom convincing.

Richard Chartres, Bishop of London

I believe in God because He has both revealed and hidden Himself in so many different ways: in the created world, the Holy Bible, the man Jesus Christ; in the Church and men and women of God through the ages; in human relationships, in culture and beauty, life and death, pain and suffering; in immortal longings, in my faltering prayers and relationship with Him. There is nothing conclusive to force me into believing, but everything sug­gestive, and constantly drawing me on into the love of Christ and to "cleave ever to the sunnier side of doubt".

David Alton, Lib Dem peer

The notion that humanity and the cosmos are an accident has always seemed implausible. A world littered with examples of complex genius - from developments in quantum theory to regenerative medicine - points us towards genius more perfect and more unfathomable than ourselves. The powerful combination of faith and reason led me as a child to believe in God.

Unsurprisingly, as I matured into manhood, that belief has not been immune against the usual catalogue of failure, sadness and grief; and belief has certainly not camouflaged the horrors of situations I have seen first hand in places such as Congo and Sudan. Paradoxically, it has been where suffering has been most acute that I have also seen the greatest faith.

By contrast, the more we own or have, the more difficulty we seem to have in seeing and encountering the Divine.

Professor Stephen R L Clark, philosopher

I believe in God because the alternatives are worse. Not believing in God would mean that we have no good reason to think that creatures such as us human beings (accidentally generated in a world without any overall purpose) have any capacity - still less any duty - to discover what the world is like.

Denying that "God exists" while still maintaining a belief in the power of reason is, in my view, ridiculous.My belief is that we need to add both that God is at least possibly incarnate among us, and that the better description of God (with all possible caveats about the difficulty of speaking about the infinite source of all being and value) is as something like a society. In other words, the Christian doctrine of the incarnation, and of the trinity, have the philosophical edge. And once those doctrines are included, it is possible to see that other parts of that tradition are important.

Nick Spencer, director of Theos, the public theology think tank

I would say I find Christianity (rather than just belief in God) the most intellectually and emotionally satisfying explanation for being.

Stephen Green, director of the fundamentalist pressure group Christian Voice

I came to faith in God through seeing the ducks on a pond in People's Park, Grimsby. It struck me that they were all doing a similar job, but had different plumage. Why was that? Why did the coot have a white beak and the moorhen a red one? Being a hard-nosed engineer, I needed an explanation that worked and the evolutionary model seemed too far-fetched and needful of too much faith!

I mean, what could possibly be the evolutionary purpose of the bars on the hen mallard's wings, which can only be seen when she flies? Or the tuft on the head of the tufted duck?

So I was drawn logically to see them as designed like that. I suppose I believed in an intelligent designer long before the idea became fashionable. So, that left me as a sort of a deist. But God gradually became more personal to me and I was drawn against all my adolescent atheist beliefs deeper and deeper into faith in Jesus Christ.

Douglas Hedley, reader in metaphysics, Clare College, Cambridge

Do values such as truth, beauty and goodness emerge out of a contingent and meaningless substrate? Or do these values reflect a transcendent domain from which this world has emerged? I incline to the latter, and this is a major reason for my belief in God.

Paul Davies, quantum physicist

I am not comfortable answering the question "Why do you believe in God?" because you haven't defined "God". In any case, as a scientist,

I prefer not to deal in "belief" but rather in the usefulness of concepts. I am sure I don't believe in any sort of god with which most readers of your article would identify.

I do, however, assume (along with all scientists) that there is a rational and intelligible scheme of things that we uncover through scientific investigation. I am uncomfortable even being linked with "a god" because of the vast baggage that this term implies (a being with a mind, able to act on matter within time, making decisions, etc).

Professor Derek Burke, biochemist and former president of Christians in Science

There are several reasons why I believe in God. First of all, as a scientist who has been privileged to live in a time of amazing scientific discoveries (I received my PhD in 1953, the year Watson and Crick discovered the structure of DNA), I have been overwhelmed by wonder at the order and intricacy of the world around us. It is like peeling skins off an onion: every time you peel off a layer, there is another one underneath, equally marvellously intricate. Surely this could not have arisen by chance? Then my belief is strengthened by reading the New Testament especially, with the accounts of that amazing person, Jesus, His teaching, His compassion, His analysis of the human condition, but above all by His resurrection. Third, I'm deeply impressed by the many Christians whom I have met who have lived often difficult lives with compassion and love. They are an inspiration to me.

Peter J Bussey, particle physicist

God is the ultimate explanation, and this includes the explanation for the existence of physical reality, for laws of nature and everything. Let me at this point deal with a commonly encountered "problem" with the existence of God, one that Richard Dawkins and others have employed.

It goes that if God is the ultimate cause or the ultimate explanation, what then is the cause of God, or the explanation for God? My reply

is that, even in our own world, it is improper to repeat the same investigatory question an indefinite number of times. For example, we ask, "Who designed St Paul's Cathedral?" and receive the reply: "Sir Christopher Wren." But, "No help whatever," objects the sceptic, "because, in that case, who then designed Sir Christopher Wren?" To this, our response will now be that it is an inappropriate question and anyone except a Martian would know that. Different questions will be relevant now.

So, likewise, it is very unlikely that we know the appropriate questions, if any, to ask about God, who is presumably outside time, and is the source of the selfsame rationality that we presume to employ to understand the universe and to frame questions about God.

What should perhaps be underlined is that, in the absence of total proof, belief in God will be to some extent a matter of choice.

Reverend Professor Michael Reiss, bioethicist and Anglican priest

At the age of 18 or 19, a religious way of understanding the world began increasingly to make sense. It did not involve in any way abandoning the scientific way. If you like, 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, if there is life after death, and so on. That was reinforced by good teaching, prayer and regular reading of scripture.

Peter Richmond, theoretical physicist

Today most people reject the supernatural but there can be no doubt that the teachings of Jesus are still relevant. And here I would differentiate these from some of the preaching of authoritarian churches, which has no doubt been the source of much that could be considered to be evil over the years. Even today, we see conflict in places such as Africa or the Middle East - killings made in the name of religion, for example. As Christians, we recognise these for what they are - evil acts perpetrated by the misguided. At a more domestic level, the marginalisation of women in the Church is another example that should be exposed for what it is: sheer prejudice by the present incumbents of the Church hierarchy. But as Christians, we can choose to make our case to change things as we try to follow the social teachings of Jesus. Compared to pagan idols, Jesus offered hope, comfort and inspiration, values that are as relevant today as they were 2,000 years ago.

David Myers, professor of psychology, Hope College, Michigan

[Our] spirituality, rooted in the developing biblical wisdom and in a faith tradition that crosses the centuries, helps make sense of the universe, gives meaning to life, opens us to the transcendent, connects us in supportive communities, provides a mandate for morality and selflessness and offers hope in the face of adversity and death.

Kenneth Miller, professor of biology, Brown University

I regard scientific rationality as the key to understanding the material basis of our existence as well as our history as a species. That's the reason why I have fought so hard against the "creationists" and those who advocate "intelligent design". They deny science and oppose scientific rationality, and I regard their ideas as a threat to a society such as ours that has been so hospitable to the scientific enterprise.

There are, however, certain questions that science cannot answer - not because we haven't figured them out yet (there are lots of those), but because they are not scientific questions at all. As the Greek philosophers used to ask, what is the good life? What is the nature of good and evil? What is the purpose to existence? My friend Richard Dawkins would ask, in response, why we should think that such questions are even important. But to most of us, I would respond, these are the most important questions of all.

What I can tell you is that the world I see, including the world I know about from science, makes more sense to me in the light of a spiritual understanding of existence and the hypo­thesis of God. Specifically, I see a moral polarity to life, a sense that "good" and "evil" are actual qualities, not social constructions, and that choosing the good life (as the Greeks meant it) is the central question of existence. Given that, the hypothesis of God conforms to what I know about the material world from science and gives that world a depth of meaning that I would find impossible without it.

Now, I certainly do not "know" that the spirit is real in the sense that you and I can agree on the evidence that DNA is real and that it is the chemical basis of genetic information. There is, after all, a reason religious belief is called "faith", and not "certainty". But it is a faith that fits, a faith that is congruent with science, and even provides a reason why science works and is of such value - because science explores that rationality of existence, a rationality that itself derives from the source of that existence.

In any case, I am happy to confess that I am a believer, and that for me, the Christian faith is the one that resonates. What I do not claim is that my religious belief, or anyone's, can meet a scientific test.

Nick Brewin, molecular biologist

A crucial component of the question depends on the definition of "God". As a scientist, the "God" that I believe in is not the same God(s) that I used to believe in. It is not the same God that my wife believes in; nor is it the same God that my six-year-old granddaughter believes in; nor is it the God that my brain-damaged and physically disabled brother believes in. Each person has their own concept of what gives value and purpose to their life. This concept of "God" is based on a combination of direct and indirect experience.

Humankind has become Godlike, in the sense that it has acquired the power to store and manipulate information. Language, books, computers and DNA genomics provide just a few illustrations of the amazing range of technologies at our fingertips. Was this all merely chance? Or should we try to make sense of the signs and wonders that are embedded in a "revealed religion"?

Perhaps by returning to the "faith" position of children or disabled adults, scientists can extend their own appreciation of the value and purpose of individual human existence. Science and religion are mutually complementary.

Hugh Ross, astrophysicist and astronomer

Astronomy fascinates me. I started serious study of the universe when I was seven. By the age of 16, I could see that Big Bang cosmology offered the best explanation for the history of the universe, and because the Big Bang implies a cosmic beginning, it would require a cosmic beginner. It seemed reasonable that a creator of such awesome capacities would speak clearly and consistently if He spoke at all. So I spent two years perusing the holy books of the world's religions to test for these characteristics. I found only one such book. The Bible stood apart: not only did it provide hundreds of "fact" statements that could be tested for accuracy, it also anticipated - thousands of years in advance - what scientists would later discover, such as the fundamental features of Big Bang cosmology.

My observation that the Bible's multiple creation narratives accurately describe hundreds of details discovered much later, and that it consistently places them in the scientifically correct sequence, convinced me all the more that the Bible must be the supernaturally inspired word of God. Discoveries in astronomy first alerted me to the existence of God, and to this day the Bible's power to anticipate scientific discoveries and predict sociopolitical events ranks as a major reason for my belief in the God of the Bible. Despite my secular upbringing, I cannot ignore the compelling evidence emerging from research into the origin of the universe, the anthropic principle, the origin of life and the origin of humanity. Theaccumulating evidence continues to point compellingly towards the God of the Bible.

Steve Fuller, philosopher/professor of sociology, University of Warwick

I am a product of a Jesuit education (before university), and my formal academic training is in history and philosophy of science, which is the field credited with showing the tight links between science and religion. While I have never been an avid churchgoer, I am strongly moved by the liberatory vision of Jesus promoted by left-wing Christians.

I take seriously the idea that we are created in the image and likeness of God, and that we may come to exercise the sorts of powers that are associated with divinity. In this regard, I am sympathetic to the dissenting, anticlerical schools of Christianity - especially Unitarianism, deism and transcendentalism, idealism and humanism. I believe that it is this general position that has informed the progressive scientific spirit.

People such as Dawkins and Christopher Hitchens like to think of themselves as promoting a progressive view of humanity, but I really do not see how Darwinism allows that at all, given its species-egalitarian view of nature (that is, humans are just one more species - no more privileged than the rest of them). As I see it, the New Atheists live a schizoid existence, where they clearly want to privilege humanity but have no metaphysical basis for doing so.

Michael J Behe, scientific advocate of intelligent design

Two primary reasons: 1) that anything exists; and 2) that we human beings can comprehend and reason. I think both of those point to God.

Denis Alexander, director, Faraday Institute for Science and Religion, Cambridge

I believe in the existence of a personal God. Viewing the universe as a creation renders it more coherent than viewing its existence as without cause. It is the intelligibility of the world that requires explanation.

Second, I am intellectually persuaded by the historical life, teaching, death and resurrection of Jesus of Nazareth, that He is indeed the

Son of God. Jesus is most readily explicable by understanding Him as the Son of God. Third, having been a Christian for more than five decades, I have experienced God through Christ over this period in worship, answered prayer and through His love. These experiences are more coherent based on the assumption that God does exist.

Mike Hulme, professor of climate change, University of East Anglia

There are many reasons - lines of evidence, if you will - all of which weave together to point me in a certain direction (much as a scientist or a jury might do before reaching a considered judgement), which we call a belief.

[I believe] because there is non-trivial historical evidence that a person called Jesus of Naza­reth rose from the dead 2,000 years ago, and

it just so happens that He predicted that He would . . . I believe because of the testimony of billions of believers, just a few of whom are known to me and in whom I trust (and hence trust their testimony).

I believe because of my ineradicable sense that certain things I see and hear about in the world warrant the non-arbitrary categories of "good" or "evil". I believe because I have not discovered a better explanation of beauty, truth and love than that they emerge in a world created - willed into being - by a God who personifies beauty, truth and love.

Andrew Zak Williams has written for the Humanist and Skeptic. His email address is: andrewbelief@gmail.com