Edward W. Said published his highly influential polemic “Orientalism” nearly 30 years ago, and Robert Irwin, a British specialist in the history and culture of the Middle East, has been fuming ever since. “Dangerous Knowledge” is his belated two-pronged response: a point-by-point rebuttal of Mr. Said, folded into a history of Western scholarship devoted to the Middle East.

Mr. Irwin delays his direct attack until the penultimate chapter but throws down the gauntlet early. “Orientalism,” which indicts the entire field of Eastern studies as racist and imperialist, he characterizes in the introduction as “a work of malignant charlatanry.”

Its distortions are so fundamental, its omissions so glaring, that the first order of business, as Mr. Irwin sees it, is to offer a dispassionate account of what Western scholars did and did not do. The exercise is worthwhile, he argues, because Mr. Said’s book “has been surprisingly effective in discrediting and demoralizing an entire tradition of scholarship.”

A survey course in West-East encounters follows, beginning with the scattered observations of the ancient Greeks and Romans, and the first attempts by Christian thinkers to make sense of Islam, a religion they interpreted as a new form of Christian heresy. Mr. Irwin points out that throughout the Middle Ages and well into the Renaissance, Muslims, to the extent that they were thought about at all, were often regarded as pious, austere and a reproach to lax Christians. Saladin, in particular, was elevated to heroic status.

“The Arabs and Turks were not regarded as barbarians, nor were they consciously regarded as non-European, for there was little or no sense of any kind of European identity in this period,” Mr. Irwin writes.

The Orient, initially regarded as a land of marvels, gradually turned into an object of study, and with the Frenchman Guillaume Postel, born in 1510, the first genuine Orientalist appears on the scene. Postel, a linguistic prodigy, learned Arabic so quickly that his teacher in Istanbul thought he might be a demon. He produced the first grammar of classical Arabic in Europe and, in other works, introduced Europeans to the life of Muhammad, the history of Islam and the culture of the Ottoman Turks. An admirer of all things Eastern, he was also, Mr. Irwin remarks casually, “a complete lunatic.”

The Orientalists described by Mr. Irwin do seem to be a colorful bunch. The field attracted eccentrics, obsessed misfits and colonial administrators driven nearly mad by boredom. Edward Palmer, a Victorian Orientalist, poet and spy, embarked on a secret government mission to bribe Bedouin tribesmen near the Suez Canal but was unfortunately murdered for the gold he carried. He reportedly cursed his killers in eloquent Arabic before being shot and thrown over a cliff.

At Oxford, Mr. Irwin studied with an Orientalist who once bicycled naked through the town, pursued by the police, whom he escaped by ditching his bicycle and swimming across the Cherwell River.

More often than not, the scholars Mr. Irwin describes took an enlightened view of the peoples and the cultures they studied. “There has been a marked tendency for Orientalists to be anti-imperialists,” he writes, “as their enthusiasm for Arab or Persian or Turkish culture often went hand in hand with a dislike of seeing those people defeated and dominated by the Italians, Russians, British or French.”

The issue of imperialism and colonialism looms large for Mr. Said and Mr. Irwin. For Mr. Said, Orientalism is both conceptually imperialist and historically a tool for imperialist adventures, especially by the French and British, who, Mr. Irwin counters, were vastly overrepresented in “Orientalism.”

The leading Orientalists of the 19th and early 20th century were Germans, but Germany had no imperial designs in the Middle East or Asia and therefore did not fit the argument, he writes. Russia, with its policy of conquest in central Asia and the Caucasus, would seem to offer ideal material for Mr. Said’s argument, Mr. Irwin notes, but mysteriously plays no role at all in “Orientalism.”

Mr. Irwin writes for a general audience in a lively, readable style. Somehow, he manages to sneak in Frankenstein’s monster (in the novel the creature reads a popular work on Egyptian ruins by the Comte de Volney, a French Orientalist) and “Dracula,” which was inspired by a lecture on Balkan superstitions by the Hungarian Orientalist Arminius Vambery. But the long roll call of unfamiliar savants, presented in lightning-quick sketches, and the profusion of obscure Arabic texts make the historical section of “Dangerous Knowledge” occasionally tough going for anyone not familiar with the field.

The payoff is Mr. Irwin’s all-out assault on Mr. Said, which makes for bracing reading, although it comes a little late in the day. Mr. Said died in 2003, and some of the arguments that Mr. Irwin advances were thrashed out by Mr. Said, Bernard Lewis, Ernest Gellner and others more than 20 years ago. As a useful aside, Mr. Irwin registers his own criticisms of Orientalist scholars, especially their blindness (shared by Mr. Said) to the rising power of Islamic fundamentalism.

What Mr. Irwin makes abundantly clear, whether he fully realizes it or not, is that “Orientalism” cannot really be refuted. No matter how many errors of fact or interpretation are exposed, the book is invulnerable because it makes a political rather than a scholarly argument. In the age of postcolonial studies, “Orientalism” continues to get an enthusiastic, even reverential hearing. It may not be right, but it feels good.

Copyright 2006 The New York Times Company