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

Cause and effect, the riddle of all history, is a particular devil in financial history; and never more so than today, where entire classes of security are collapsing not on public exchanges and stock-tickers but because there are no markets to establish prices this side of nothing.

Osama bin Laden, the Saudi-born revolutionary who is believed by most Arab and Iranian observers to be the inspiration of the attacks in New York and Washington, is the best known of the Islamic militants to have emerged in the past 20 years and the least difficult to fathom.

What holds an Arab leader in power is a mixture of violence and prestige. Both President Assad and King Hussein were felt to have defended Arab interests against the world. That, in the end, is more important than what they wear on their head.

Since the attack on the United States on September 11 2001, and the US retaliation in Afghanistan and Iraq, there must be few people who have not felt a twinge of nostalgia for the cold war.

Bulls don't read. Bears read financial history. As markets fall to bits, the bears dust off the Dutch tulip mania of 1637, the Banque Royale of 1719-20, the railway speculation of the 1840s, the great crash of 1929.

Losing your capital is like losing your trousers. It is a real humiliation, and one not to be soon repeated.