Nature is not simply a technical or economical resource, and human beings are not mere numbers. To suggest that one can somehow align all the squabbling institutions of science, environmental management, government and diplomacy in an alliance of convenience to regulate the global climate seems to me optimistic.

The truth is, of course, that history is not completed in modern commerce any more than philosophy is perfected in political economy. In other words, there is nothing timeless or God-given about filling stations and penicillin and plastic bags.

The year 2008 was a reminder to those who had forgotten that there is such a thing as history and that the cycle of famine and feast in commerce, first identified in antiquity and well understood in the Middle Ages, was not suddenly abolished in modern times.

If good history is dispassionate history, it must naturally wait until the passions of the period subside.

One of the consequences of the Iranian revolution has been an explosion of history. A country once known only from British consular reports and intrepid travelogues is now awash with historical documents, letters, diaries, grainy video, weblogs and secret police files of questionable authenticity.