"Why are most Africans, unless forced by dire necessity to earn their livelihood with 'the sweat of their brow', so loath to undertake any work that dirties the hands?"

"The all-encompassing preoccupation with sex in the African mind emerges clearly in two manifestations ..."

"In the African view of human nature, no person is supposed to be able to maintain incessant, uninterrupted control over himself. Any event that is outside routine everyday occurrence can trigger such a loss of control ... Once aroused, African hostility will vent itself indiscriminately on all outsiders."

These statements, I think you'll agree, are thoroughly offensive. You would probably imagine them to be the musings of some 19th century colonialist. In fact, they come from a book promoted by its US publisher as "one of the great classics of cultural studies", and described by Publisher's Weekly as "admirable", "full of insight" and with "an impressive spread of scholarship".

The book is not actually about Africans. Instead, it takes some of the hoariest old prejudices about black people and applies them to Arabs.

Replace the word "African" in the quotations above with the word "Arab", and you have them as they appear in the book. It is, the book says, the Arabs who are lazy, sex-obsessed, and apt to turn violent over the slightest little thing.

Writing about Arabs, rather than black people, in these terms apparently makes all the difference between a racist smear and an admirable work of scholarship.

The book in question is called The Arab Mind, and is by Raphael Patai, a cultural anthropologist who taught at several US universities, including Columbia and Princeton.

I must admit that, despite having spent some years studying Arabic language and culture, I had not heard of this alleged masterpiece until last week, when the investigative journalist Seymour Hersh mentioned it in an article for New Yorker magazine.

Hersh was discussing the chain of command that led US troops to torture Iraqi prisoners. Referring specifically to the sexual nature of some of this abuse, he wrote: "The notion that Arabs are particularly vulnerable to sexual humiliation became a talking point among pro-war Washington conservatives in the months before the March 2003 invasion of Iraq.

"One book that was frequently cited was The Arab Mind ... the book includes a 25-page chapter on Arabs and sex, depicting sex as a taboo vested with shame and repression."

Hersh continued: "The Patai book, an academic told me, was 'the bible of the neocons on Arab behaviour'. In their discussions, he said, two themes emerged - 'one, that Arabs only understand force, and two, that the biggest weakness of Arabs is shame and humiliation'."

Last week, my own further enquiries about the book revealed something even more alarming. Not only is it the bible of neocon headbangers, but it is also the bible on Arab behaviour for the US military.

According to one professor at a US military college, The Arab Mind is "probably the single most popular and widely read book on the Arabs in the US military". It is even used as a textbook for officers at the JFK special warfare school in Fort Bragg.

In some ways, the book's appeal to the military is easy to understand, because it gives a superficially coherent view of the Arab enemy and their supposed personality defects. It is also readily digestible, uncomplicated by nuances and caveats, and has lots of juicy quotes, a generous helping of sex, and no academic jargon.

The State Department, too, used to take an interest in the book, although it seemingly no longer does. At one stage, the training department gave free copies to officials when they were posted to US embassies in the Middle East.

In contrast, opinions of Patai's book among Middle East experts at US universities are almost universally scathing. "The best use for this volume, if any, is as a doorstop," one commented. "The book is old, and a thoroughly discredited form of scholarship," said another.

None of the academics I contacted thought the book suitable for serious study, although Georgetown University once invited students to analyse it as "an example of bad, biased social science".

There is a lot wrong with The Arab Mind apart from its racism: the title, for a start. Although the Arab countries certainly have their distinctive characteristics, the idea that 200 million people, from Morocco to the Gulf, living in rural villages, urban metropolises and (very rarely these days) desert tents, think with some sort of single, collective mind is utterly ridiculous.

The result is a collection of outrageously broad - and often suspect - generalisations. Patai asserts, for example, that Arabs "hate" the west.

He backs up this claim with two quotations: one from a book published in the mid-50s ("Most westerners have simply no inkling of how deep and fierce is the hate, especially of the west, that has gripped the modernising Arab"), and another from Bernard Lewis - currently the neocons' favourite historian - referring to the mood of "many, if not most Arabs" in 1955 (just before the Suez crisis).

We are also informed (page 144) of "the Arab view that masturbation is far more shameful than visiting prostitutes".

Whether this is why Iraqi prisoners were forced to masturbate in front of cameras is unclear, but the only supporting evidence for Patai's claim is a survey of Arab and US students published in 1954: the US students admitted to masturbating twice as often as the Arabs, while 59% of the Arabs, but only 28% of the Americans, said they had visited a prostitute during the previous 12 months.

In "outlying areas", such as Siwa oasis in Egypt, Patai says, "homosexuality is the rule, and practised completely in the open". This unequivocal statement is based on accounts dating from 1935, 1936 and 1950, and, in a footnote, Patai concedes that they "need to be checked out by an anthropologically trained observer".

There is also a good deal of confusion in the book between the present and the past. An Arab man, Patai writes, even if he has four wives, "can have sexual relations with concubines (slave girls whom he owns)".

All this adds up to an overwhelmingly negative picture of the Arabs. Positive characteristics are mentioned, but are given relatively short shrift.

Hospitality and generosity - two highly regarded virtues in Arab societies - get three and one and a half pages respectively, compared with a whole chapter devoted to alleged sexual hang-ups.

The book is a classic case of orientalism which, by focusing on what Edward Said called the "otherness" of Arab culture, sets up barriers that can then be exploited for political purposes.

The Arab Mind was originally published in 1976, but - according to one US academic - actually belongs to the "national character" genre of writing that was popular in comparative politics around the middle of the last century.

Its methodology, therefore - not to mention much of its content - was considerably behind the times even when it first appeared.

Patai died in 1996, but his book was revived by Hatherleigh Press in 2002 (nicely timed for the war in Iraq), and reprinted with an enthusiastic introduction by Norvell "Tex" De Atkine, a former US army colonel and the head of Middle East studies at Fort Bragg.

"It is essential reading," De Atkine wrote. "At the institution where I teach military officers, The Arab Mind forms the basis of my cultural instruction."

In a speech last week, the US president, George Bush, congratulated himself on having removed "hateful propaganda" from the schools in Iraq.

Perhaps it is now time he turned his attention to military schools in the US.