Even then, it gets right down to the roots of personality. Clive Calver, the Secretary of the Evangelical Alliance, tells a story about his mother dying: "Mum had lost language, she had forgotten how to speak, and she was so upset. The last coherent thing she ever said was a prayer: `Dear Lord, I don't know who I am; I don't know what I am; and I don't know where I am. But please love me.'
"And it strikes me that when your body is riddled with cancer, as hers was, and your mind is scrambled by Alzheimer's, you can still know and love God, and he's still there, and that's why I'm sure I know God."
Everyone I spoke to for this article is a leader of some constituency, whose experience of God is trusted by others. Monica Furlong has been a hugely influential campaigner for feminist understandings of Christianity. Akram Khan Cheema has led the fight for Muslim schools in Bradford, and organised what will probably be the first Muslim school to get government funding. Clive Calver claims to speak for more than a million evangelical Christians - certainly the most self-confident religious lobby in Britain at the moment. John McIndoe, as Moderator of the General Assembly of the Church of Scotland, heads a sort of Government-in-exile of the Scottish people: the Church of Scotland is simultaneously closer to the nation and further from the state than the established Church of England.
A sense of God is notoriously not the same as the sense of God. In fact, the same sense may lead people to diametrically different conclusions and bitter rivalry. Four of our subjects are men whose religious convictions must put them perpetually at loggerheads with each other. Dr Jonathan Sacks, the Chief Rabbi of the United Synagogue, may be at peace with Akram Khan Cheema, the Muslim; but with his cousin David Goldberg, the senior rabbi of the Liberal Jewish Synagogue, relations are distinctly frosty. And Ian Paisley finds himself here among men he believes will burn forever.
Religions are communities of the imagination, and communities have always had boundaries, beyond which dangerous strangers dwell. There are other contradictions about being a spiritual leader. The modern medias demand from anyone who would become famous an infinite capacity to repeat the same slogans, so that by the time you actually become a recognised spiritual leader, you may have nothing left to say. There will certainly be very little
The media demands for anyone who would be famous an infinite capacity to repeat slogans. When you become a spiritual leader, you may have nothing to say
of your private and intimate relationships you will want to reveal to the press. Dr Jonathan Sacks, for example, when asked about God, talks almost entirely about "Jewish" responses rather than his own.
"Jews tend to find God in simple rather than majestic things - a glass of wine, a loaf of bread, songs over the Sabbath table," he avers. "Someone once said that Judaism is more about the prose than the poetry of spiritual life. Above all, we find it in human relationships, the sharing of joys, the comfort of friends. Judaism is not a religion of solitude. It is noisy, argumentative, social."
Judaism is not alone in this. No one, it seems, goes out into the wilderness to listen to Him any more. "You find God in spiritual teachers and mentors, not a voice from nowhere," says Dr Sacks. And James Crampsey, the Jesuit, adds, "One of the joys of being a priest is seeing God at work in the way people live their struggles and celebrate their joys."
Akram Khan Cheema, one of the founders of Feversham College, an all-girl Muslim secondary school in Bradford, comes from a religion where God and community are wholly entwined. That is a large part of the reason why Islam seems so dangerous and alien to the secular West.
"As I understand it," he says, "there are two distinct groups of knowledge - one is revealed, which is contained in the Book, and the other, which is all around us. The revealed knowledge gives me the backbone - without that, the rest of the knowledge would be very materialistic and of less significance. One tries to interpret that revealed knowledge because you read the Koran every day and every day it can mean slightly different things. I don't want to be like the very pious people who didn't have any knowledge, or the very knowledgeable person who didn't have piety - I want to be increasing in knowledge every moment of my life, and work towards being pious."
We are so used to thinking of God as something or someone experienced personally that it can come as a shock to discover how much this experience is bound up in particular communities. To Jonathan Sacks, the discovery came in the middle of the Six Days War of 1967. He was at Cambridge then, reading philosophy, a believing but not very devout Jew. The threat to the survival of Israel gripped him profoundly. "I just got the feeling that what was at stake was more than military. It wasn't a voice: it was more like hearing the beginning of a sentence and wanting to hear the end."
So this earnest young man set off on a pilgrimage around the USA on a Greyhound bus, looking for teachers. The ones he found, and who most impressed him, were figures almost from before the dawn of modernity. The most famous was the Lubavitcher Rebbe, who died last year - though some of his followers refused to believe it. Menachem Mendel Schneerson, the Rebbe, was regarded as the Messiah by the enormously energetic sect he led, and it seemed to some of its members that such a man could not die. He was certainly one of the most influential figures in the world-wide revival of Jewish fundamentalism.
"He was a majestic and awe-inspiring figure," Sacks recalls, "more so than any I've met, but, when you actually sat alone in the room with him, there was only one person in the room, and that was you. He could efface himself towards you totally, and bring out something in you that you did not know was there. He asked, `What are you doing for Jewish life in Cambridge?' I found very quickly a mantle of leadership being placed over me. He was a leader who was not interested in creating followers but in creating leaders."
But leaders, once created, have a thankless task. Dr Sacks has been fiercely criticised for his behaviour towards the late Rabbi Hugo Gryn, who, as a Reform Jew, did not acknowledge his authority. He, in turn, will not acknowledge Hugo Gryn was a rabbi. Though Dr Sacks paid his respects as a private citizen to Hugo Gryn's family, he did not attend the funeral, and, when he attended a memorial service, did so on "interfaith" grounds. This upset the Lubavitch, who felt that even to attend a memorial service risked recognising Reform Jewry, as much as it infuriated the liberal wings of Anglo-Jewry.
Where was God in all that? I asked: "Weeping, I should think. The Jewish community has always seen itself as an extended family, and God as a parent, and there are times when families are very fractious. But I do sometimes feel that we could do more to bring God into our communal life. That would require a capacity for humility, reverence, restraint."
And going to each others' services? I couldn't resist asking.
"No. No. No. Not that."
A week to the day after our conversation, the Jewish Chronicle published a private letter from Dr Sacks to an elderly, ultra-Orthodox rabbi about his part in Gryn's memorial service. "Only your honour can know," he wrote, "what conflict I experience in praising a person who is among those who destroy the faith."
Sacks's most public critic may well be his cousin by marriage, David J Goldberg, who is the senior rabbi at the Liberal Jewish Synagogue in London's St John's Wood. When he heard of my breakfast with Dr Sacks, he insisted on giving me a slap-up breakfast himself. Yet when he talks of God, the impishness quite goes out of him:
"My approach has always been cerebral - probably too cerebral, which is why I'm not as good a leader as I should be. Spinoza talked about the intellectual love of God - that's what I've striven for.
"I've always been Englishly diffident about taking his name too easily. My favourite quote on the subject is from the Anglican theologian Richard Hooker: `Concerning God, our safest eloquence is our silence.'"
But Goldberg is not a man who finds safe eloquence easy. "I'm very envious of those people who claim to know God personally," he went on. "I never have that sense of a deeply intimate companionship. But I've always thrilled to the notion of the workings of the universe. That, I must confess, is where I can see God. What I've done personally is to remove Him from the universe. I don't hold Him guilty for the death of a child, any more than I thank Him for Israel's victory in the Six Day War. The only way I cope with God is by taking the view that having created the world, He voluntarily retired from it and wouldn't intervene."
For him, it is totally pointless to worship a finite god. "I want my God to be an all-powerful, all perfect God, otherwise there's no point."
All my subjects felt that sometimes God did seem to withdraw from the world or from them. "I think that, for many people, when the absence of God is shouting very loudly in our lives, it's difficult to hear the gentle whisper of God's love," admitted James Crampsey, the Jesuit. "Every person, myself included, has to face areas of brokenness. Then I have to take myself into the space where Jesus was in his suffering and death. I have to try to hear some expression of God's loving me in that very brokenness."
Crampsey, born in Glasgow in 1946, has been a Jesuit for all his adult life. The Jesuits have the most rigorous training of any of the major Catholic orders, and a reputation as the Pope's front-line troops. His predecessor as leader of the Jesuit Province of England, Scotland (and Guyana), Michael Campbell-Johnston, has gone back to El Salvador, where six of their colleagues were murdered by the army during the civil war. Yet that killing, he says, does not worry him nearly as much as does the suffering of innocents:
"I had a very strong experience of this when I went to Dachau, to the Jewish memorial. It's shaped like a small crematorium - to go down into it is like going down into the grave, but, when you reach the bottom, you can look up through the darkness, and at the top of the chimney is a small strip of copper that just catches the light." That, to him, is a perfect image of the promise of God's love, even in the horrendous suffering of innocents. "It's not gold, but copper will do, I think."
Compare this with Akram Khan Cheema's steely belief in fate. The Muslim idea that your fate is predetermined is terribly misunderstood, he says. It is not fatalism or resignation. "It's coming to terms with what actually does take place in the world. I really have no idea why dreadful things happen in the face of a loving, caring God. You have to say `it happened because it was the will of God'."
This is not so far from the ideas of John McIndoe, Moderator of the Church of Scotland. His approach to God, he says, is rooted in thanksgiving. The Greek for "thank you", evkaristo, is cognate with "Eucharist", the central Christian ceremony. The sense of gratitude to be alive, which wells up inside all of us, must come from God and be directed to God, he feels. "Where is gratitude without God?"
But you need grit as well, he added: "On those occasions in life when I could not truly be thankful, I regard the faith as being a matter of showing a degree of doggedness, even stoicism, without abandoning one's belief that ultimately there will still be cause for thanksgiving."
Clive Calver, the General Secretary of the Evangelical Alliance for 14 years, believes, from experience, in conversion. He had been brought up in a Christian family but lost his faith in the Sixties. "But when I was 19, in the East End of London, and part of the radical, protesting generation, I met a preacher, a guy named Roger Forster - he bored me to tears."
He pauses for a moment. Years of preaching have left him with fine comic timing. "The problem I had was that he and his wife and their two little children shared their home by the Thames with any druggy, dosser, alcoholic - anyone who wanted a bed for the night and some food. Now, being a blunt East Ender, I said, `what have you got', and he said `Jesus'. It was two weeks later I gave my life to Christ, because of what I saw. I didn't want a faith that gave me an escapist cop-out - I wanted a faith that made me live differently."
Six months later, abandoning his vague ambitions for a political career, he enrolled in London Bible College, and later married the principal's daughter. He now talks in certainties, but the longer he talks, the less clear it becomes of what exactly it is that he's certain. Take miracles. The Evangelical Alliance believes in miracles - even though it expelled Morris Cerullo for promising them in his fund-raising letters - and Calver says that he trusts God for them constantly. Yet they do not need to involve anything supernatural. His youngest daughter was born with grand mal epilepsy. When she was four, two things happened. His church prayed for her; and the doctors increased her dosage of anti-convulsant drugs. She has not had a fit since then, and the treatment has gradually tapered off.
"Doctors will tell you it's a miracle of modern medicine, and the church will tell you it's the power of intercessory prayer. But I don't care how God did it," he says.
The first thing that Ian Paisley said, when I asked him about the knowledge of God, was also the first thing that James Crampsey, the Jesuit, had said: We can't know God; He can only reveal himself to us. To Paisley, this revelation is available to anyone who reads the Bible: "There's only one conclusion that you can come to if you read the Bible, and that's the idea that Christ is the only saviour. This idea that the Bible is all very hard to understand is utter nonsense. The Bible is written by God to reveal Himself to man, and it's clear. That's why the Roman Catholics try to hide it."
Paisley is, I think, the only Christian I have met in the last 10 years who actually believes the sort of things that atheists claim all Christians must believe. We talked between votes, in a lobby at the House of Commons - or rather, I listened. He likes talking about theology, and has cascades of argument ready for every problem. At one point, he looked up and gestured at the ornate Victoriana round us. "If you had been sitting in this same city a hundred years ago, you would have found that every Christian talked as I do."
He was right, of course. He's unnervingly familiar with those days. He asked about my family, and named three Victorian Protestant preachers named Brown: were any of them related?
"I am looked upon as an antiquarian and a fool, but the gospel is the only thing that saves," he said. When he started preaching, he explained, in a small country congregation, there were 64 people there. "And when I'd preached for six months, there were 30 left." He gave a great carnivorous laugh. "Then God started to talk - public houses were closed around there, gambling houses were closed down... and now there are 1,250 children in my Sunday school in each week. I was despised, hated, and laughed at. They said I was a fool. I may be a fool, but the gospel I preach is the gospel that saves. If the whole world believed as I believe, I wouldn't think I was on a moral pathway."
Paisley carries in his breast pocket a New Testament, bound in brown leather, like a diary, which he pulls out to demonstrate particular quotations. "The reason you don't know what I'm saying is simply because you yourself have not the experience. The Bible tells me that - `the natural man knows not the things of the spirit'."
This doctrine allows him to dismiss any objections my natural reasons might raise to his belief in the literal truth of the Bible. If I had accepted Christ, he argued, I would see that it must all be true. How could he know, I asked, that he was himself saved? One of the difficulties of pure high Calvinism has always been that, since God alone saves for his own inscrutable reasons, neither goodness nor piety nor any other human merit can assure us of salvation. But Paisley is more confident than his forebears. "The inner witness of the Spirit is given - the Spirit gives witness to our spirit that we are the children of God."
So, in the end, even with Ian Paisley, it all seems to come down to a feeling: an assurance that is emotional as much as mental. And it is not the case that everyone who has not this feeling will go to hell. "I believe that all infants who die in infancy are atoned in the work of Christ, along with those that haven't their proper mental abilities."
But those are the only exceptions. Catholics, of course, are damned forever, along with all Anglicans, Methodists and Christians who are less than satisfactorily fundamentalis: "Modernistic apostates are everywhere now." And so, most probably, are you, gentle reader.
None the less, he started off agreeing with a Jesuit and ended up agreeing with Monica Furlong, a feminist Anglican: "If you could explain God to me, then there is something wrong - because God is a mystery." He may have meant this as a debating block, but I think he meant something more by it, too.
As a writer, Monica Furlong has had more of her intuitions trusted than almost anyone else I talked to. Many who disagree with her about religion trust her stories about the experience of God.
"What I know is mystery," she says, "which sometimes is wonderful and ecstatic, and sometimes terrifying and awful. I give it the name God because I don't know what else to call it; and only in the area of religion does there seem to be a language which discusses what I'm trying to talk about.
"Of course, I have had lots of ups and down, but the best moments in life were when the eternal erupted into the transitory. I am haunted by that experience: I might be happier if I could live without it. I don't think I can."
I don't think, for all the explanations we have been offered, that we can get closer to a sense of God than that intimation of necessary mystery