Misled? I'll just consult my stars

Our age has provided a dose of aversion therapy to the practice of reason; and Francis Wheen's book has to be read as a compendium of and guide to all the modern forms and manifestations of irrationalism. If you look up Enlightenment on Amazon, 1,500 titles come up, but most of them are stuff such as Crystal Enlightenment , Golf for Enlightenment , Awakening the Buddha within - not what either Newton or Diderot had in mind.

In our time, reason has gone home and given up on the human race. Instead, we are haunted, and hunted, by a series of grotesque nostrums and fundamentalisms, ranging from Reagonomics and Thatcherism to Islamicism and New Age Mysticism. Tony Blair has given support to the teaching of Creationism. The Reagans took no important step without consulting an astrologer in San Francisco. Two centuries during which the Western world triumphed in the spirit of progress have been succeeded by an upsurge in quackery - political, religious, psychological, cultural and ideological. Wheen sees us all as victims of the pandemic of ensuing gibberish. His canvas is vast.

Amusing though this 300-page tirade is, it would be quite wrong to dismiss it as a harmless bit of fun. We have all been caught up at some point or other in some of the episodes of nonsense that Wheen skilfully excoriates: who of us was really immune to the Diana madness? Who never succumbed, even for a week or two, to the tulip-madness of the dotcom lunacy? Which investor did not fall at some point for the lies of Enron and its dizzying stock escalations? We are all in some sense guilty - apart from Wheen himself, of course, who does not admit to a moment's backsliding in respect of Enlightenment values.

Deregulation, privatisation and globalisation are all evidence of irrational or fundamentalist belief: for all of them have entailed the abandonment of reason, secularism and empiricism. The book is a series of set-piece scenes, some of them hilarious, some of them duly shocking, in which the whole of our contemporary civilisation, if such it be, is debunked down to its toenails.

The cult of deregulation was a process by which a number of entrepreneurs were permitted to go in for daylight robbery of the assets of thousands of small savers, under cover of a kind of economic millenarianism. The internet entrepreneurs took their cue from pre-Enlightenment alchemists: Yahoo's share price rose 584 per cent in a single mad year, and simultaneously Amazon's rose by 970 per cent. As stocks rose, with no visible profits in sight, self-appointed media gurus proclaimed a New Economy, a stage in history in which values could rise relentlessly, at exponential multiples of turnover or profit, with no one able to turn them back until the shock of daylight finally broke in.

As leaders of industry abandoned financial realities, they compounded their fantasies of identity by taking the advice of style gurus: Benetton, which sells clothing, pretended to be a third-world lobbying society; merchant banks re-groomed themselves to look like advertising agencies; advertising agencies started to look like nightclubs. Chicness was all.

Wheen's destruction of prevailing myth becomes painful as it reaches our own decade, even down to the events of this year. For example, there was a time when Noam Chomsky, the most frequently cited of 20th-century intellectuals, did not believe that Pol Pot had committed genocide in Cambodia, and when Parisian leftists proclaimed the Ayatollah Khomenei a sort of liberation theologian (like the priests in South America) and his regime as the first postmodern revolution. Today, there are bestselling French intellectuals (and British websites) who believe that no planes flew into the Pentagon and World Trade Center, merely bombs thrown by the CIA, while others declare that American action in Kosovo somehow extenuates or renders morally neutral the frenzied actions of al-Qaeda fundamentalism.

This is conviction journalism of a high order, as the world has come to expect of this author. There are moments when the reader does feel that Wheen might be over-egging his pudding, perhaps even trying to sweep the argument along on the fuel of his hilarious enthusiasm. But his hits are palpable, well aimed and embarrassing to most of his readers.

We have all been tempted, if only for a brief moment, to toy with one of the loopy creeds peddled by cranks, priests or wholly respectable politicians. The further we travel in time from the disciplines imposed by the triumvirs of classical rationalism, Bacon, Locke and Newton, the easier it is to fall for the temptations of what Wheen calls "the enfeebling legacy of postmodernism... a refusal to observe any qualitative difference between reasonable hypotheses and swirling hogwash". This book is a necessary read.

Anthony Smith is president, Magdalen College, Oxford.