Al Gore is probably the most prominent of those still trying to engage us in a debate about population, but I guess most of us are fairly difficult to engage. Familiarity breeds contempt with problems; like the inevitability of death and the mind-boggling size of the universe, n billion people and rising is best forgotten on a day-to-day basis. Thinking constructively about population also poses ideological difficulties for most people, starting with the major religions, but continuing also to their humanist descendants: any account of human rights is surely going to include the right to have children? Ehrlich has been attacked by the Left, including the "green" Left, for not realising that the threat to the planet can only come from the maldistribution of resources, not from numbers. The pro-capitalists attack him for not understanding the indefinitely large possibilities of innovation. We haven't absorbed any of the rhetoric of the theory of overpopulation and still talk of anything that will increase the death rate, even among the old, as calamity and catastrophe. We are as far away as ever on having the sort of debate about a maximum age envisaged in Anthony Trollope's The Fixed Period  (published in 1882) and it is inconceivable that the committee would agree on 67 & a half, which is what happens in the novel.

In other words the disappearance of overpopulation from the political agenda is largely a consequence of ideological dogma and mental laziness. It is too easy for a politician to say brusquely, as Harold Wilson once did when asked what his government's population policy was, that he hasn't got one. But it doesn't help that most of the demographic gurus persistently overstate their case. Ehrlich has written with horror of an experience of the crowded streets of India, suggesting a kind of psychopathological misanthropy. As with several American, Canadian and Australian writers on this subject he seems to take a peculiar horror in the kind of densities of population sustained in the UK and the Netherlands. In the early stages of his career he predicted "complete collapse" for our country by 2000 and has talked of the Netherlands in similar terms. He has also predicted the worst famine in history in India and vast increases in commodity prices, none of which has actually happened. You would not put him up against Warren Buffet as a prophet or tipster. His defenders have claimed these were "scenarios" to provoke thought, rather than predictions, but their effect has been like that of the boy who cried "wolf".

The most legitimate reason for optimism is a version of the embourgeoisement thesis which has been around for over a century. This says that education and prosperity break the traditional link between progeny and wealth and create incentives to limit family size. With the help of contraception this leads to a dramatic drop in birth rates. In some times and places, including most of Europe over the last thirty years, this has appeared to work fully, though it was more evident in Britain in the 1970s than since: it is a freak demographic fact that there were twice as many births in 1946, when I was born, than in 1977, when my eldest son was born. The effect has spread to many countries, though not all by any means, and its effects in Europe are largely mitigated by greatly increased migration.