A CRITIC, A COMIC, A HISTORIAN, a philosopher, and an amateur theologian walk into a bar. “Hello, Professor Eagleton,” the barman says, “What will it be?” If this joke is at all funny, that is because it leads one to expect an interaction between five people who turn out, absurdly, to be one. How could a single person be so many things? But the joke is unoriginal, and the setup is technically flawed. Since the subject of the sentence is singular, the verb should be “walks” not “walk.”

All of which is to show that jokes fall in the scope of rational explanation. We can give reasons why something is funny or why it is not, why a joke works or why it doesn’t. These reasons aren’t just causes, triggers that inhibit or provoke an unintelligible laugh. They help us to make sense of humor.

Like many writers on this topic, Terry Eagleton begins his new book, Humour, by owning the complaint that to analyze humor is to kill it. In fact, Eagleton goes meta: he begins by noting that many writers on the topic begin by noting this and he notes that it isn’t always true. The British comedian Stewart Lee, who may be the best stand-up working today, makes a trademark of analyzing jokes on stage in order to critique the audience response. When we attempt to explain a joke, what we are doing is continuous with this; it is what stand-ups do, to wonderful effect, on Stuart Goldsmith’s podcast The Comedian’s Comedian.

If there is nothing wrong with explaining jokes, something very different is afoot when the theorist of humor bursts upon the scene and ventures to explain the essence of the funny. It’s a bemusing bid, an almost comical collision of metaphysics and mirth. Eagleton doesn’t quite avoid its pitfalls, but he does a lot besides. His book is about the semiotics of laughter and the history of humor, not just what it means to be funny. He is rambling and inconclusive, but he is always entertaining. In the book’s opening chapter, Eagleton begins with 10 pages on laughter, its official topic, before wheeling through Freud and other thinkers for 25 more. It is easy to enjoy the ride.

A closing chapter on the politics of humor draws on the work of Russian theorist Mikhail Bakhtin, tracing hostility to humor in ancient and medieval Europe through Bakhtin’s celebration of the carnival, which he extolled as “free and unrestricted, full of ambivalent laughter, blasphemy, the profanation of everything sacred, full of debasing and obscenities, familiar contact with everyone and everything.” “In Bakhtin’s view,” Eagleton writes, “the grotesque or carnivalesque body is unfinished, open-ended, perpetually in process. As such, it is a riposte to the timeless, absolute status of official ideologies.” Comedy as revolution? Eagleton follows Bakhtin almost to the edge before he swerves, in a game of intellectual chicken. We have to accept “[t]he rather more tedious truth” that humor may reinforce the status quo as well as subvert it, and that the norms it does subvert may be ones we hoped to preserve: “[C]arnival may be a fictionalised form of insurrection,” Eagleton ruefully concludes, “but it also provides a safety valve for such subversive energies.”

It’s frustrating to be met with such balanced judgment: one looks to Eagleton for provocation and polemic. He is famous for his takedowns of postmodernism, on one front, and the “new atheists,” on the other. This book is more good-humored, and so it is more difficult to find the crux. What is most intriguing in Humour, I think, is not the setup or the punch line, the beginning or the end, but the tentative theory of humor in the middle; and even there, what is most intriguing is what kind of theory it is meant to be.

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Before the Enlightenment, Western philosophy was largely indifferent or hostile to humor. Plato associates laughter with loss of self-control and, while Aristotle advocates a mean between buffoonery and boorishness, the Stoic philosopher Epictetus is reputed never to have laughed at all. It is not that there were no funny philosophers. When he heard Plato’s account of man as the featherless biped, Diogenes the Cynic brought a plucked chicken to the door of the Academy, proclaiming, “Here is Plato’s man.” But humor was not a significant topic in ancient philosophy.

The standard philosophical theories of humor derive from philosophers of the 18th and 19th centuries. The first use of “humor” in its modern sense appears in Shaftesbury’s 1709 “Sensus Communis: An Essay on the Freedom of Wit and Humour,” which anticipates the Freudian theory of laughter as the relief of pent-up tension. A competing theory of humor — as incongruity — was pioneered by the Scottish philosopher Francis Hutcheson in 1725, before attracting such heavyweights as Kant and Schopenhauer. Its pinnacle may be Schopenhauer’s “Theory of the Ludicrous,” in which the grim philosopher dutifully explains a series of jokes. For instance:

The soldiers in the guard-room [allow] a prisoner, just brought in, [to] take part in their game of cards, but because he cheats, a dispute occurs, and they throw him out. They allow themselves to be guided by the general concept “Bad companions are turned out,” but forget that he is at the same time under arrest, i.e., a man whom they ought to keep in custody.

The antagonist behind these developments was Thomas Hobbes, who traced a person’s laughter to “[s]udden glory […] caused either by some sudden act of their own, that pleaseth them; or by the apprehension of some deformed thing in another, by comparison whereof they suddenly applaud themselves.” Eagleton has a good, ironic time mocking what has come to be known as the superiority theory of humor. Not all humor involves superiority, he notes, and not all superiority is funny: “We do not thrash helplessly on the floor because babies cannot grasp the principles of set theory or snakes find it hard to operate dishwashers.”

The snake’s inability is not inherently funny, but the image of the snake at the dishwasher does elicit a laugh. It also points toward a better theory: that the funny is a form of incongruity. Broadly sympathetic to this theory, Eagleton finds the present-day obscurity of its inventor, Hutcheson, “something of a scandal.” In his Reflections Upon Laughter and Remarks Upon the Fable of Bees, Hutcheson wrote:

That then which seems generally the cause of laughter, is “the bringing together of images which have contrary additional ideas, as well as some resemblance in the principal idea: this contrast between ideas of grandeur, dignity, sanctity, perfection, and ideas of meanness, baseness, profanity, seems to be the very spirit of burlesque; and the greatest part of our raillery and jest is founded upon it.

I think it is fair to say that the greatest part of Eagleton’s jest is founded on the contrast between grandeur and baseness. The demotic or deflating analogy is his go-to gag. “For some of its critics,” he wrote in 2004’s After Theory, “the very idea of cultural theory is a contradiction in terms, rather like ‘fascist intellectual’ or ‘Alabaman haute cuisine.’ […] Isn’t a theory of art rather like trying to have a science of scowling or cuddling?” If there is less of this in Humour than in other Eagleton books, that may be in part because his subjects here are less inflated to begin with and in part because there are actual jokes to be discussed.

Despite being partial to Hutcheson, Eagleton does not accept the incongruity theory of humor as it stands. The problem, he says,

is that it is descriptive rather than explanatory. It tells us what we laugh at, but not why we do so. What is needed, then, is to splice the incongruity thesis with the release theory [Freud’s account of laughter as relief of psychic energy], which is indeed an explanatory move. […] [H]umour happens for the most part when some fleeting disruption of a well-ordered world of meaning loosens the grip of the reality principle.

Eagleton disarms the would-be critic by conceding that incongruity-plus-relief is neither necessary nor sufficient for humor and by insisting that an approximate theory can still be useful, “rather as a fuzzy photograph of someone can be better than no photograph at all, and a job worth doing is usually worth doing badly.” His theory neglects the humor of derision, which need not be incongruous, though it does involve a trespass on social norms. A more encompassing view might advert to this, as in “Jokes,” an essay by the anthropologist Mary Douglas: “A joke is a play upon form. [… It] affords opportunity for realising that an accepted pattern has no necessity.”

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The problem with all such theories is not that they are approximate but that, even if humor involves the violation of expectations or norms, this won’t tell us which violations are funny and which are not: it won’t distinguish comic incongruity from tragic irony. The failure is so evident that it makes one wonder what a theory of humor was supposed to be. Was it ever intended to answer these questions? What is the ambition of the comic philosopher? Talk about “fuzzy photographs” is unhelpful, and Eagleton’s argument only adds to the puzzle. When he complains that the incongruity theory is “descriptive rather than explanatory,” what kind of explanation does he want? He is not talking about the ordinary explanation of jokes nor does he turn to the science of humor. Instead, he tries to explain why incongruity, which we might expect to be frustrating, should give pleasure. His answer is that it affords a pleasant break from the hard work of maintaining our sense of reality, of “congruence, coherence, consistency, logic, linearity.” The idea has a certain attraction, I suppose, but humor can supply all sorts of human needs and it is unclear why the pleasure of the funny must make sense in other terms, why it must satisfy a need or desire other than the need or desire for humor. Incongruity is pleasant when and because it is funny.

We need to take a step back. Before we dive into theories of humor, we need to know what these theories are for. Why is humor a subject for philosophy at all? Of course, we can ask, “What is it to be funny?” as Plato asked, “What is it to be just?” or, “What is knowledge?” But we can also ask, “What is it to be muddy?” or, “What is Alabaman haute cuisine?” Since the question can be asked for any value of X, we need some reason to think that asking it is fruitful here and now. A philosophical theory of justice aims for a standard of justice that will guide our actions. Does a philosophical theory of humor aim for a standard of humor that will guide our jokes? By that measure, the familiar theories (relief, superiority, incongruity) are hopeless. They are also hopelessly ahistorical. Humor is a moving target and, while the humor of ancient Rome may have something in common with the humor of Tristram Shandy and the humor of Tina Fey, the highest common factor will be low.

When we turn from the history of humor to the history of philosophy we find a clue to the philosophical significance of the funny. Having neglected it for so long, why did philosophers begin to study humor in earnest around the 18th century? Eagleton traces the rise of interest in humor to the Scottish Enlightenment. Philosophers such as Hutcheson, David Hume, and Adam Smith would place the sentiments at the heart of civil society. Our sympathy with one another is what makes it possible for us to live together in relative peace. No wonder they approved of humor as an innocent pleasure shared. Some went so far as to model the moral sense on the sense of humor, or vice versa: our appreciation of virtue, like our appreciation of jokes, is a matter of human sensibility.

Eagleton disputes the analogy: “If humour is an image of the good life,” he protests, “then virtue must be as spontaneous as laughter, in which case how can it be a question of merit?” But this objection is doubly unjust. For one thing, the spontaneity of laughter coexists with the giving and taking of reasons, as when we explain a joke. For another, Eagleton gets the analogy wrong. What is akin to laughter for Hutcheson and Hume is not moral virtue (being good) but moral judgment (recognizing who is and is not good). Virtue is indeed a question of merit; approbation of virtue, in ourselves and others, is not.

Humor is philosophically interesting because amusement can be justified — we can give reasons why something is funny or not — without any expectation that the reasons we give speak to rational beings, as such. It is not as though anything capable of thinking or reasoning must have a sense of humor. It is simply that we do. We can recognize this without undermining humor or concluding that nothing is funny. We shouldn’t be embarrassed that the basis of a certain kind of value goes no deeper than the facts of human life. For the philosophical sentimentalist, this is true of values in general. We can give reasons for respecting other people, reasons why justice is a virtue, reasons why it matters how we live, but these will be, at best, reasons for human beings, ones that draw on our capacity to sympathize with one another. We may hope that the moral sense is less subjective than the sense of humor, that it is not so relative to history or culture. But we cannot step outside our humanity to explain, as if to some alien intelligence, why it should sympathize like us. A being with another form of life might be as puzzled by our attitude to justice as it is when we laugh at jokes.

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This way of thinking can induce intellectual vertigo, the philosophical equivalent of standing on a glass bridge over the Grand Canyon. There is a sense of insufficiency, of needing solid ground: a desire to transcend our lives and justify them to anything that can think, to the universe itself. This is why we crave Plato’s forms, which guide us from outside the sensible world, or Kant’s categorical imperative, in which morality flows from the mere possibility of freedom. There is a human propensity to wonder, “Why?” and a form of incongruity, the violation of a norm or expectation, when there is no answer to be had. The momentum of the question sends us racing off a cliff and we find ourselves running on thin air, like Wile E. Coyote.

Here the sense of humor turns back on itself, and on the human condition, to ask, “How should we feel about the mismatch between our desire for reasons and the reality that reasons must give out?” Is this the sort of incongruity that is funny or the sort that is not? Reactions vary. For Albert Camus, “[t]he absurd is born of this confrontation between the human need [for reasons] and the unreasonable silence of the world.” Our predicament is no joke. For Eagleton, by contrast, “comedy represents a momentary respite from the tyrannical legibility of the world.”

The question of how to feel about the fact that reasons end, and that they end with us, is itself a demand for reasons that is subject to the same momentum. It is one thing to explain the joke, to give reasons why we should smile at the hopelessly frustrated urge for intelligibility, or not. But there is a call for more, for a reason that transcends the human practice of explaining jokes, a reason that would speak to anyone or anything. Can we find that reason? The human tragedy, or comedy, is that we can’t.

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Kieran Setiya teaches philosophy at the Massachusetts Institute of Technology and is the author of Midlife: A Philosophical Guide (Princeton University Press, 2017).