I've been a rabbi full-time for 25 years, and worked for the community for at least five before that. I care deeply about my work - the contact with people at serious moments in their lives, the listening, the caring, the teaching, the sharing. Being a community minister has done the opposite of making me cynical: it's taught me to appreciate life's richness and great depth.

I enjoy writing, and find it a great challenge. But it gives me distance from the immediate demands of the moment, and gives me perspective for reflection.

I studied English literature at Cambridge, and have always loved language, the struggle to find the right words, to be truthful to facts and feelings.

My father was not a rabbi, but his father was, and he came from a rabbinic line.

My wife is Nicola Solomon, executive director of the Society of Authors. We have three children: a son of 20, Mossy; Libbi, who is 17; and Kadya, who is 15 - and numerous animals. We love books. Libby is studying Classics and German, and there's lots of Hebrew around.

I wrote The Eternal Journey: Meditations on the Jewish year to try to reflect the depth and beauty of the festivals. The Silence of Dark Water: An inner journey is an attempt to explore heart, mind, conscience, and mortality - what it means to be human. Neither book is intended solely for a Jewish audience, and I have had appreciative feedback from committed Christian readers.

The latest, Walking with the Light: From Frankfurt to Finchley, tells of a walk to bring a flame from the Eternal Light of my grandfather's former synagogue in Frankfurt back to London, to light with it the flame of our new synagogue here in Finchley. I was very moved by the fact that my grandfather wrote in his memoirs of how, though the inside of the synagogue was trashed and burnt by the Nazis on Kristall-nacht, the Eternal Light kept burning. People took this as a sign from God.

I quickly dismissed the idea of carrying a naked flame like a pseudo-Olympic runner. I brought the light as an LED torch in the outside pocket of my rucksack, and recharged it at night. It made life a lot less dangerous. (The flames in both synagogues now are electric.)

I spent a year-and-half preparing the walk. It was very hard initially to make the contacts, and at times I thought: "It's not going to happen." At such moments I felt low; but the walk itself was a challenging, deepening experience.

I was invited to speak in the synagogue in Frankfurt, where my grandfather had officiated for 30 years. That moved me very deeply.

The worst day was the last on the Continent, because of the bitter driving wind and rain. A tug had overturned in the harbour of Hook of Holland, and two sailors had been drowned. Walking through that weather and finding out that that had happened . . . When I got home, I wrote to their families, because I felt somehow connected with them because of walking through that same weather.

The idea of the light which burns through darkness, the lights of understanding, courage, hope, humanity, stirred me. The walk was a kind of modern pilgrimage, in which I met Christians, Jews, and Muslims, and reflected on moral and spiritual light and dark.

My beloved Border Collie had to come with me. That's him now, barking at imaginary sheep. (Mitzpah! Come here!) After all, why go on a three-week walk and leave him behind? He was wonderful company, and his joyous running and dancing was a counter-balance to the sometimes sombre themes of the walk.

Guy, who directed the film about my walk, would ambush me en route at unexpected moments. He always refused to tell me what he was going to ask me about.

The night after the sabbath had ended, I went with Guy to a laundrette in the centre of Cologne. There, in the last half-hour before the place closed, with Mitzpah comfortably curled up on the seat opposite, he asked me about God. I remember watching the washing spin round in the machine, and thinking of the earth turning on its axis in the vast, immeasurable, and unimaginable universe. God? A personal God whose will we could influence through prayer? Was it possible to believe in such a being any more?

God is the totality of the as-yet- unexplained vitality and consciousness within the universe, which animates all life in its unendingly varied forms, and is yet a profound unity.

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This God inspires the love which, in my best and purest moments, fills my heart. This God inspires the awe which sometimes sweeps through my heart with fear and beauty, humbling and fulfilling me at once.

That's what I think I mean by God. But, like the washing spinning round in that machine, my thoughts are always provisional, turning and changing before the vastness of this unbounded reality.

Guy then asked me whether God was there to be a source of comfort. I answered both yes and no: yes, because God inspires the love in our hearts and unites all consciousness, thus turning life into a great bond of companionship; no, because, when the earth dehydrates, or the sun explodes, or our entire solar system is sucked into some black hole, God will still exist. Ultimately, God is not for our comfort; God is because God is.

I think it may be different from my grandfather's faith; but the depths of our faith are always personal, almost secret, and so I feel cautious about speaking for my grandfather. But, although he lived through the First World War and the Holocaust, he grew up in an age when faith may have been clearer, less challenged both by science and by recent history.

We don't often hear the narratives of groups of people different from our own. I often think of Cain's excuse after killing his brother: "I don't know. Am I my brother's keeper?" The second part of the sentence is always quoted, but I'm also gripped by the first. Had he indeed really "known" his brother, would he have felt able to kill him?

Peace will only be made real in the world through the capacity to listen to and feel for each other's stories. As a Jew, as a descendant of an often marginalised and persecuted minority, I'm acutely conscious of what it means to listen to the outsider.

For myself, the experience of meeting Israelis, Arabs, and Palestinians, being in their homes, inviting them to speak to us, has been very important. My community goes out of its way to support organisations that build bridges between these communities.

Religion can easily become a form of nationalism, with all the violence which accompanies it. Too often we mistake our own religion, our path, for the goal itself, as if the religion were, in fact, God, and not a way of trying to discover God. Then, instead of deepening our hearts and broadening our moral and spiritual vision, religion narrows us down and becomes a form of idolatry, the worship of detail. The other then becomes the unbeliever, the God-denier. This is a terrible ill.

Closeness to other faiths, listening to their liturgies, friendships with members of other religions, can and should lead us to a deeper discovery of God and the sacred, both in their insights and perceptions, and more deeply within our own tradition.

I see it as a religious and moral imperative to do what we can to protect the world we live in.

My favourite places are Scotland: the hills, waterfalls, lochs, forests, the coast, long walks. . . And Israel: Jerusalem, the Galilee, especially in spring, the orange groves, the scent of jasmine, the Carmel, and its forests and deer.

I'm fascinated by the book of Job. I love the classic Rabbinic literature, the Talmud, the rabbinic Midrash, and the stories around them. There's very little I don't find engaging. And contemporary theology, as well. 

I last got angry over something stupid. I find the petty issues more draining than the serious issues of suffering and its meanings, life and its values, and death.

I'm happiest with my family, walking, reading, studying, listening, lost in writing, gardening, in moments of silence, in places of beauty. All of these are touched by God's presence.

I'm not sure about praying "for" - though I often do it, and it is perfectly legitimate within Judaism. I think, at depth, prayer is seeking to be in the presence of God, in quiet.

I'd choose to be locked in a synagogue with my wife, or one of my children, and the dog. Actually, not the dog. He'd find it much harder to be locked in. Yes, synagogues vary on this, but he has special permission to be in mine.

Jonathan Wittenberg is Rabbi of the New North London Synagogue. He was talking to Terence Handley MacMath. Walking With The Light is published by Quartet Books at £20.