Last week the Chief Rabbi published a book that was seized upon with (even to him) surprising avidity: two newspapers ran extracts, the Times devoted a leader to it, and the journalist Clifford Longley, who admittedly wrote the preface, announced decidedly that "there can be few more important books published this decade". The book was mentioned approvingly in a Guardian political column, and Sacks was invited on to the Today programme to expound his views.
Faith in the Future is about morality, and so about the family, which Sacks sees as "the arena of the central moral crisis of our time". His argument is that the collectivism of the 1970s is not, as is popularly imagined, the opposite of the individualism of the 1980s, but its symbiotic partner: the state has enabled individualism to flourish by detaching us from previous forms of authority - parents, traditions, community. And while some of the resulting freedoms have been refreshing, they have left many people uncertain of their values.
In this he is at one with communitarians like Amitai Etzioni and with right-wing academics like Charles Murray, who argue for a reassertion of moral absolutes (such as the one that children need two parents). Sacks makes this case more cogently and lucidly than any other Briton has yet done. And inevitably, coming from a religion steeped in centuries of tradition (and which is, as he has said, only as strong as its families) he argues that we need to look to tradition to find again a moral core to our lives.
It is very easy for the happily married to be prescriptive about other people's lives, and Sacks is extremely happily married. A few weeks ago he told his wife the one thing he regretted "was that I didn't do it sooner. It took me all of three weeks to propose, and I seriously regret that I was so slow." He was 22, his wife Elaine was 21, and she and their three children (Joshua, 20, Dina, 18 and Gila, 12) "have been everything to me".
So does his hoped for "moral restructuring" confuse happiness, which may be fortuitous, with effortful virtue? What would he say, for example, to a bitterly unhappy married woman who is convinced she would be better off as a single parent? "Judaism has never attached a stigma to divorce, and domestic violence can be good grounds. It does seem though that we haven't got to grips with educating children in what it means to sustain a long-term relationship. Very often domestic violence evolves from a failure to praise one another, to resolve problems. To have high expectations of marriage is no bad thing, but to be willing to break it off because of immediate difficulty is not good. I do think that we have taken public policy decisions on the basis of very abstract and detraditionalised moral systems such as utilitarianism, which turns out to be rather bad at differentiating between short-term states like pleasure and long-term states like happiness."
A further problem with Sacks's "politics of responsibility" may be its gender blindness. The traditional family relied upon women whose identity and satisfaction lay entirely in marriage and motherhood, and if the contemporary version is unstable, it's partly because women refuse to make a choice that men have never had to make, between paid work and being a parent. Dr Sacks denies - rather offendedly - that he wants women back at the kitchen sink. "My grandmother ran the family wine business in the East End, while my grandfather sat in the back office reading books. In very orthodox circles the woman is often the breadwinner, while men study well into married life. The Jewish community has never linked the family, which is centred around a great deal of religious observance, with a particular set of economic circumstances."
Which is all very well in theory, but in the modern economy the "time- famine" remains a serious problem for many working parents. It is hard to have a family life through which morality courses like lifeblood if you are only occasionally there.
The people with whom Sacks really takes issue, one suspects, are members of what have been called the new knowledge class: "people in the media, at the cutting edge of the professions, in corporate finance, new technologies and so on. My feeling is that what works for them doesn't necessarily work for everyone. They are capable of very rapid adaptation - which is what makes them good at their jobs - but it is very destabilising if the whole population adopts those values."
Dr Sacks describes himself as a liberal - "of the sort who sees the need for tradition rather than radical social experiments". And when, three and a half years ago, he succeeded Lord Jakobovits, who had been virtually canonised by Margaret Thatcher, he was hailed as a very different kind of Chief Rabbi. He was young (47 last week) and as much the product of English universities as of rabbinical seminaries.
He spent his earliest years in the East End, and most of his childhood in Finchley, where he attended Christ's College, the local grammar school. "I remember asking my father about Judaism when I was about five, and he said, `I can't tell you about these things because I didn't have a good education (he sold cloth in the East End) but one day you will be able to tell me'."
Jonathan and his three younger brothers "set some kind of record" by all going to the same college at Cambridge and getting firsts. This, he says, not unseriously, "is what being a Jewish parent is all about". All four boys became more religious than their parents, although Jonathan is the only one to have become a rabbi - a decision that had its beginnings in the outbreak of the Six Day War when he was a philosophy undergraduate at Cambridge. "It looked as if Israel was about to face a devastating war on three fronts, and that made me realise that something terrible had happened before I was born, and something terrible was happening now. From then on I was tracking my roots, my feeling of connection to this group of people 7,000 miles away. It was, if you like, a personal search for identity, for community."
Impressed by the thoughts of 50 American rabbis interviewed in the magazine Commentary, he flew to America, bought a Greyhound bus ticket, turned up on their doorsteps and announced that he had come 3,000 miles to see them. "In this way I spoke to virtually all the leading thinkers of the Jewish community." He went to a traditional yeshiva (rabbinical seminary) after Cambridge, took his doctorate at Oxford and London, and taught philosophy at Middlesex Polytechnic while studying at Jews' College, of which he eventually became principal.
As Chief Rabbi, he represents "between two-thirds and three-quarters of the Jewish community, depending on how you count it". But to do the job as he wants - to represent the whole community as far as possible - he must maintain good relations with both the liberal and reform, and ultra orthodox wings. He has already disappointed both: his is not an easy job when there is growing assimilation and secularisation on one hand, and a drift to the right on the other.
He set out initially to "communicate a Judaism that was completely loyal in traditional faith, but capable of saying things that were morally challenging and morally inspiring". He is careful to avoid statements that could be construed as party political, but inevitably he is seen as politically tough. Clever as he is, and liberal as he may be, the truth is that the office of Chief Rabbi doesn't leave much room for anything but toughness. But while he may understand human frailty, he is severe about the need for human virtue. In this respect his views come straight out of his orthodoxy, and they are uncompromising. Nor are they going away. Dr Sacks could stay in the job until 2018. "I never give up," he says, "until I have achieved what I set out to achieve."