Fashionable Nonsense was published in 1997 in France, and in 1998 in the United States. As part of the so-called science wars, the book criticizes postmodernism in academia for what it claims are misuses of scientific and mathematical concepts in postmodern writing. Within the humanities, the response to the book was bitterly divided. Some were delighted, some enraged; reaction was polarized between impassioned supporters and equally impassioned opponents of Sokal. Critics of Sokal and Bricmont charge that they lack understanding of the writing they were criticizing. Responses from the scientific community were far more blunt and supportive.
The book includes long extracts from the works of Jacques Lacan, Julia Kristeva, Paul Virilio, Gilles Deleuze, Luce Irigaray, Bruno Latour, and Jean Baudrillard who are considered by some to be leading academics of Continental philosophy, critical theory, psychoanalysis or social sciences. Sokal and Bricmont set out to show how those intellectuals have used concepts from the physical sciences and mathematics incorrectly. The extracts are intentionally rather long to avoid accusations of taking sentences out of context.
Sokal and Bricmont claim that they do not intend to analyze postmodernist thought in general. They aim to draw attention to the abuse of concepts from mathematics and physics, where abuse means:
The book gives a chapter to each of the above mentioned authors, "the tip of iceberg" of a group of intellectual practices that can be described as "mystification, deliberately obscure language, confused thinking and the misuse of scientific concepts." For example, Luce Irigaray is criticised for asserting that E=mc2 is a "sexed equation" because "it privileges the speed of light over other speeds that are vitally necessary to us"; and for asserting that fluid mechanics is unfairly neglected because it deals with "feminine" fluids in contrast to "masculine" rigid mechanics. Similarly, Lacan is criticized for drawing analogies between topology and mental illness that, in Sokal and Bricmont's view, are unsupported by any argument and are "not just false: [they] are gibberish".
Sokal and Bricmont highlight the rising tide of what they call cognitive relativism, the belief that there are no objective truths but only local beliefs. They argue that this view is held by a number of people, including people who the authors label "postmodernists" and the Strong Programme in the sociology of science, and that it is illogical, impractical, and dangerous. Their aim is "not to criticize the left, but to help defend it from a trendy segment of itself. Quoting Michael Albert, "there is nothing truthful, wise, humane, or strategic about confusing hostility to injustice and oppression, which is leftist, with hostility to science and rationality, which is nonsense.
Richard Dawkins, (speaking about Lacan) in a review of this book said "We do not need the mathematical expertise of Sokal and Bricmont to assure us that the author of this stuff is a fake. Perhaps he is genuine when he speaks of non-scientific subjects? But a philosopher who is caught equating the erectile organ to the square root of minus one has, for my money, blown his credentials when it comes to things that I don’t know anything about."
The book has been subject to heavy criticism by post-modern philosophers and otherwise scholars with some interest in continental philosophy. Bruce Fink (who did the first complete English translation of Jacques Lacan's Ecrits) offers a critique in his book Lacan to the Letter, where he accuses Sokal and Bricmont of demanding that "serious writing" do nothing other than "convey clear meanings". Fink asserts that some concepts which Sokal and Bricmont consider arbitrary or meaningless do have roots in the history of linguistics, and that Lacan is explicitly using mathematical concepts in a metaphoric way, not claiming that his concepts are mathematically founded. He takes Sokal and Bricmont to task for elevating a disagreement with Lacan's choice of writing styles to an attack on his thought, which, in Fink's assessment, they fail to understand. Fink says that "Lacan could easily assume that his faithful seminar public... would go to the library or the bookstore and 'bone up' on at least some of his passing allusions".
Although Fink acknowledges that Lacan is difficult to read, admitting that "most of us — even those of us who devote a lot of time and energy to deciphering Lacan's work — become infuriated with him for it at one point or another," he also accuses Sokal and Bricmont of having "no idea whatsoever what Lacan is up to Sokal and Bricmont tacitly admit as much, saying that they "readily admit that we do not always understand the rest of these authors' work". Their position is that they are merely critiquing the misuse of scientific and mathematical concepts, which, as scientists, they do understand.
This latter point, however, is disputed by critics such as Arkady Plotnitsky, who holds graduate degrees in both mathematics and literature. He suggests four central problems with Sokal and Bricmont. First, they lack familiarity with the subject matter and context of the works that they criticize. Second, they ignore the historical contexts of the use of mathematics and science. Third, they generally show a lack of aptitude for philosophy. Fourth, they do not show an understanding of the history or philosophy of mathematics and science, and indeed display less understanding of the mathematics than Lacan does in some areas. Plotnitsky particularly holds that "some of their claims concerning mathematical objects in question and specifically complex numbers are incorrect, making their attack on Lacan for similar errors particularly egregious.