Dennis Healey once compared a verbal attack by one of his parliamentary colleagues to "being savaged by a dead sheep." I was reminded of this remark when I met the physicist Alan Sokal, the man who, along with mathematician Jean Bricmont, has caused outrage and indignation among the French intelligentsia first with his spoof post-modern article published in the journal Social Text, and then for his and Bricmont’s book Intellectual Impostures, which combines a catalogue of misuses of scientific terms by predominantly French thinkers with a stinging attack on what they call "sloppy relativism"

Given this history, you’d expect Sokal to be more lupine than lamb-like, but in fact, he is a friendly, chatty, effusive figure more interested in offering his guests his favourite blackcurrant tea from New York than character assassinations. You would have thought he and Healey’s sheep would be just about level in terms of terrifyingness, so how did this gentle man come to be the scourge of the rive gauche?

"My original motivation had to do with epistemic relativism," explains Sokal, "and what I saw as a rise in sloppily thought-out relativism, being the kind of unexamined zeitgeist of large areas of the American humanities and some parts of the social sciences. In particular I had political motivations because I was worried about the extent to which that relativism was identified with certain parts of the academic left and I also consider myself on the left and consider that to be a suicidal attitude for the American left."

Sokal’s intention was to write a parody of this kind of relativism and to see if an academic journal would publish it. The end result was "Transgressing the Boundaries: Towards a Transformative Hermeneutics of Quantum Gravity", which was published in the journal Social Text in 1996. With extensive quotations from the thinkers Sokal was targeting, such as Lacan, Irigaray and Baudrillard, the article pulls off the powerful trick of constructing the parody almost entirely out of the parodied (something which, ironically, some of the post-modernists Sokal attacks would surely appreciate).

"It’s important not to exaggerate what the parody shows," stresses Sokal. "As an experiment it doesn’t prove very much. It just proves that one journal was very sloppy in its standards. I don’t know what other journals would have done. I suspect that a lot of other journals would have rejected it. As for the content of the parody, in some ways it’s a lot worse than a lot of stuff which is published, in some ways it’s a lot less bad. Steve Weinberg in his article in the New York Review of Books made, I think, a perceptive observation, that ‘contrary to what some people have said, I don’t think that Sokal’s article is incomprehensible. I find some of the views in it daffy. But I think that most of the time he expresses himself clearly and indeed I have the distinct impression that Sokal finds it difficult to write unclearly,’ which is absolutely true. I had to go through many revisions before the article reached the desired level of unclarity.

"It was a parody, intended to be extreme. It comes out in the first two paragraphs, and says, without any evidence or argument – of course it says it in high-faluting language, but translated into English it basically says – "Most western intellectuals used to believe that there exists a real world, but now we know better."

By the time the parody had been published and Sokal had revealed the hoax, provoking a storm that became big news in the quality press in France, Britain and America, the original target had been extended.

"As I did the research for the parody, I came up against the other issue, namely, the gross abuse of terminology from the natural sciences in the writings both of French, American and British authors, but the French ones are the more prominent, they’re the big stars."

The parody was thus to spawn a book, Intellectual Impostures, covering both relativism and the abuses of science. "It was the second aspect that became the most sensational aspect of the book, but it was the question of relativism that motivated me."

However, the coverage of the two themes in one book has perhaps back-fired, in that readers have confused the two issues.

"One thing that I have to emphasise over and over and over again, and which we emphasise in the preface to the English edition, but somehow it doesn’t seem to sink in, is that there are really essentially two books under one cover, which are only weakly related. There is the critique of the gross abuses of scientific concepts by certain French philosophical literary intellectuals – they’re not all philosophers in the strict sense. Then, on the other hand, there’s various versions of epistemic relativism which we criticise and in that case the targets are mainly British and American, not French, and the two debates are on very different planes. They have to be evaluated completely separately, the targets are different. We do not accuse the authors of the imposture of relativism. In some cases it’s not clear what their philosophy is and we don’t make any attempt to judge their philosophy. On the other hand the authors of relativism, we don’t accuse them of imposture, we accuse them of ambiguous writing or sloppy thinking, but certainly not of trying to misrepresent things. So they’re completely separate and the link between them is primarily sociological. There’s only a very weak logical link between them."

Sokal’s frustration that people don’t notice this separation, when it is so clearly stated in the preface, tells you all you need to know about what motivates him: he just can’t stand it when people fail to notice clear, logical distinctions, and having to repeat them until people do get it just irritates him more. Critics have claimed that this scientific insistence on clear, neat distinctions just isn’t relevant to the texts he lampoons. Sokal is not impressed by the objection, voiced most explicitly by John Sturrocks in the London Review of Books. "Sokal and Bricmont," wrote Sturrocks, "apply criteria of rigour and univocity fundamental to their own practice which are beside the point once transferred to this alien context."

"What criteria of rigour are we talking about?" asks a frankly baffled Sokal. "Are we talking about criteria that a sentence should mean something relatively determinate; that the words in it should mean something and have some relevance to the subject in hand; that there ought to be a logical argument from one sentence to another; that when you’re talking about some external phenomena, the facts about those phenomena are relevant – I mean, we’re upholding the minimal standards of evidence and logic that I would have thought would be taken for granted by anybody in any field."

What of the idea that there’s a certain value to be had simply in a kind of liberal attitude to ideas? Sturrocks goes on to say, "Far better wild and contentious theses of this sort [Irigaray’s] than the stultifying rigour so inappropriately demanded by Sokal and Bricmont."

"But," retorts Sokal, "he doesn’t say what is stultifying about the idea that the sentences should mean something and that there should be some logical connection. If he thinks it is important for crazy ideas to be out there and not suppressed, then fair enough. But these crazy ideas are out there, so the question is, ‘should they be out there and criticised, or out there and uncriticised?’ He seems to be saying that they should be out there and uncriticised, that it’s unfair to point out that these wild and contentious theses are in fact crazy."

What if we take an extreme defence and say that vagueness and ambiguity are actually great virtues in writing because they open up possibilities, which, again, Sturrocks suggests. Sokal will have none of it.

"Well in poetry it’s a great virtue, in novels it might be a great virtue. But I do think that in analytical writing, whether it’s about physics or biology or history or sociology, the goal should be to remove ambiguity when possible. Of course, natural language is unavoidably ambiguous, but we should do our best. If we’re trying to talk about some external objects then we should try to make as clear as possible what external objects we are talking about and what we’re saying about them.

"When the book came out in France, Jean-François Lyotard agreed to be on a television programme with Bricmont and me and we had a kind of debate. Unfortunately it wasn’t a very serious programme. Also, unfortunately the fifteen minute debate consisted of a ten-minute monologue by Lyotard in very flowery French, which, if I understood him correctly, he was saying that physicists don’t understand that words are used in a different way in poetry and novels than they are in physics books. When we finally got to the floor, we said, ‘Well, we know that, but to our knowledge the books of Lacan and Delouze are not sold in the poetry section of bookstores, they are sold in psychology and philosophy, so they should be judge by the standards of psychology and philosophy – those are cognitive discourses, they are purporting to say something about something, let’s judge them that way. If you want to re-classify them as poetry, then we can judge them on whether they’re good poetry or not.’ My personal feeling would be most of these people don’t write good poetry either. Lacan, I don’t think writes good poetry."

However, there were times reading the book when I felt a bit uncomfortable in the sense that it felt like, in the first part of the book, we were just having a laugh at these foolish people. Where was the sincere attempt at trying to see what the interpretations are? I read passage upon passage where I thought, "Well, someone, presumably, would be able to come in and interpret this in a way which might make sense."

"Let’s not leave this as an abstract question in the air," insists Sokal. "This is an open challenge to defenders of all these people. We would love for people to pick one or more passages in the book where we criticise particular texts and explain first of all what they mean, justify the references to mathematics and physics and explain why it’s valid. So far, no-one has taken up our challenge. There was one article in La Recherche where two Lacanians tried – rather vainly I thought – to defend Lacan’s square-root of minus-one and the erectile organ. But aside from that, the whole debate has just been abstract defences of the right to metaphor – which we grant, explicitly – but without trying defend any specific one of the texts."

So in this whole affair no-one has shed light on any of those passages?

"Not only shed light. Aside from that one article [in La Recherche], I don’t know if anyone has even selected a passage from the text that we’ve criticised and tried to explain what it means. Not a single one. It’s all in some ethereal plane, the discussion. Our goal is limited. We did not try to understand or to discuss in the book the role of topology within Lacan’s psychoanalysis – that would be far beyond our competence. We’d almost certainly get it wrong, we’d certainly be accused of getting it wrong. We’re already stepping far enough out of our field to write the book. You can imagine if we’d tried to explain how mathematics functions within Lacan’s psychoanalysis, within Kristeva’s theory of poetic language and so on - we’d have our heads cut off. That’s not the purpose of the book. I think we’ve given good evidence that whatever Lacan may be trying to do in psychoanalysis, the mathematical theory of compact sets or imaginary numbers is irrelevant to it, or at the very least that he hasn’t explained the relevance."

Although Sokal is not interested in attacking the Philosophy of Science in general, in Intellectual Impostures, Sokal says, "Science is a rational enterprise, but difficult to codify." This remark, coupled with his repeated defence of the rationality of science without reference to any overarching theory of science, made me wonder if there were any philosophers of science with whom he could find some agreement.

"I have respect for a lot of philosophers of science," says Sokal, but admits "I don’t think I agree with the systems of any of them. For example, we criticise Popper on various grounds, although we respect him in other ways. We criticise some of the more extreme formulation of Kuhn and so on, but agree with him in other ways. The same with Feyreraband. Maybe our view is somewhat closer to Lakatos, I don’t know.

"I don’t have anything against philosophers who try to specify it [the scientific method], and I think John Worrall was critical because he thought we had underestimated the extent to which it can be codified, and to which some philosophers – he mentioned Lakatos – had succeeded in codifying it. That’s a more subtle question that I’d love to discus with him. But our dispute is not primarily with philosophers of science. We’re more worried about the gross abuses and gross exaggerations of these ideas which originated in philosophy of science but which have trickled down in vulgarised form to anthropology and cultural studies. People just talk about the incommensurability of paradigms as if it were an established fact."

Sokal tries to maintain a tricky equilibrium between his strongly-held views about relativism and his avowed disinterest in getting drawn into subtler philosophical debates. Whether this is tenable is unclear. Very few people are crude relativists, as Sokal acknowledges. So then doesn’t he have to get involved in the subtler philosophical issues if he wants his case to stick?

This perhaps came out in a lengthy exchange I had with Sokal about the differences between idealism, relativism and instrumentalism. Idealists believe that there is no such thing as a mind-independent reality, but it doesn’t follow from this that science is not objective. Relativists believe that there is no one truth about reality. Instrumentalist believe that science is not about discovering the nature of reality, but a means of predicting and manipulating the world. These positions can all be classified as non-realist, in that they deny either the existence of a world independent of minds, or at least deny that such a world can be known. Sokal, who sees himself as a moderate realist, is strongly opposed to relativism and less stridently opposed to instrumentalism. But if a broad idealism is behind a lot of the thinkers he criticises, and that is distinct from instrumentalism and relativism, then he’s not only missed his target, he’s also not really in the right ball-park.

I say this, not to criticise the limits of Sokal’s philosophical knowledge (it’s abundantly clear that Sokal is much clearer in his understanding of philosophy than some of his targets are about the science they appropriate), nor because I am sure that idealism is behind a lot of what Sokal criticises, but rather to illustrate the perils of Sokal’s enterprise. He wants to avoid the subtle distinctions and stick to the gross errors. But is it not possible that some of these only appear as gross errors because of a lack of understanding of the subtler ideas underlying them?

Sokal insists that, "The debate I was trying to raise was much cruder. We give the example of the anthropologist and two theories of the origin of native American populations, One that they came from Asia, which is the archaeological consensus, the other the traditional native American creation myths, so that their ancestors always lived in the Americas and the anthropologists said, ‘Science is just one of many ways of knowing the world. The Zuni world-view is just as valid as the archaeological viewpoint of what prehistory is all about.’ So we go through and try and disentangle what he means by ‘just as valid’. There are certain interpretations of that which are unobjectionable but don’t say much, there are other versions that do say something significant which we think are grossly false. Jean and I were in Brazil in April and there was two-day seminar at the University of Sao Paolo about our book and things related to it, and we had long discussions with anthropologists who really refused to admit that a culture’s cosmology could be objectively true or false. Their beliefs about the origin of the universe, or the movements of the planets or whatever, could only be judged true or false relative to a culture. Not just questions of cosmology, questions of history. And we asked, ‘Does that mean that the fact that millions of native Americans died in the wake of the European invasion, is that not an objective fact, that it’s merely a belief that’s held to be true in some cultures?’ We never got a straightforward answer from them."

Whether or not Sokal is right in his accusations, his methods, particularly the parody, have been criticised on some fronts for undermining certain important things, such as trust. Does perhaps the ridiculing of an area of academia bring the whole intellectual community into disrepute?

"There’s certainly a danger. I have to emphasise that I didn’t expect that this would ever reach the man on the street. It certainly wasn’t intended to reach the front page of the New York Times or the front page of the Observer or the front page of La Monde. It happened that way. A month before it came out in Social Text, I was discussing with my friends, ‘How big is this likely to be?’ My prediction was that it would be a significant scandal within a small academic community. It would be page ten of the Chronicle of Higher Education [The American equivalent of The Times Higher] and maybe a 50-50 chance of a brief mention on the New York Times education page. So I certainly didn’t expect that it would make the popular press and, indeed, when it did, some of the articles in the popular press, even in the so-called serious press like the New York Times gave off a whiff of anti-intellectualism, which I’ve tried to criticise in my writings since then. We criticise the political twist that the New York Times gave it, for example.

"So yes, it was briefly used. It dropped out of the popular press pretty fast, which is fine by me. I intended it to cause a debate in academia and that’s what I think it has done. But, yes, in the popular press it had briefly two negative effects. It was used to bash intellectuals in general and it was used to bash the political left in general. At every opportunity I’ve had I’ve argued against both of those two misuses. It’s not an attack on intellectuals in general. It’s a critique by some intellectuals of other intellectuals. And it’s not an attack of the left in general, it’s a critique by someone on the left against others on the left."

As a physicist criticising people in the humanities, I wonder if Sokal has ever felt like an impostor.

"No. I’ve felt lots of times that perhaps I’m getting in over my head, which is a totally different thing. We emphasise in the introduction that everybody has the right to express their ideas about anything, regardless of whatever their professional credentials are, and the value of the intervention has to determined by its contents, not by the presence or absence of professional credentials. So physicists can say perfectly stupid things about physics or the philosophy of physics and non-physicists can say perfectly smart things about physics, it depends upon what’s being said. So, of course, sometimes I’m a little scared because I know I’m venturing outside of the area of my primary competence. A lot of the book is on our area of primary competence, namely mathematics and physics, but one chapter is on philosophy of science, which is a little bit out of our area, so, of course I’m a little worried that perhaps I’ve made some stupid mistake and the philosophers are going to take us to task for it. If we made some stupid mistakes I want to be taken to task for it. If we’ve made gross errors or even subtle errors in the philosophy of science I want to be criticised, but not because I’m a physicist or because I lack a degree in philosophy. That’s irrelevant."

As Sokal prepares to return to his "first love", physics, how have his perceptions of the humanities and social sciences been changed by the experience of writing the parody and book?

"The best thing about this whole affair for me, which has now taken about three years of my life, has been that I’ve been able to meet and sometimes become good friends with really interesting people in history, philosophy and sociology that I wouldn’t have otherwise met. From then I’ve found out both that things were worse than I thought, in the sense that some of the sloppy thinking was spread more widely than I thought and also that things were better than I thought in there were a lot of people within the humanities and social sciences who had been arguing against sloppy thinking for years and often were not being heard. After the parody and again after the book I got an incredible amount of email from people in the humanities and social sciences and people on the political left as well, who were saying, ‘Thank you. We’ve been trying to say this for years without getting through, and maybe it was necessary for an outsider to come in and shake up our field and say that our local emperor is running naked.’"

Intellectual Impostures is published by Profile Books and is available in paperback at £9.99