The first interesting thing about fun is that many may seek it but few can define it, which makes it similar to happiness, except that with fun no one even seems to wish to attempt definition. For the fun practitioners part of the attraction is escape from the burden of thought. And for those who abhor fun, the increasing demand for it is too depressing to think about, evidence of a decadent culture, hedonistic, frivolous, lazy … and doomed. Wasn’t it foodie blowouts and swinger parties that caused the fall of Rome?

There is of course no shortage of hedonistic indulgence, from binge drinking for the indigent to luxury cruises for the affluent. Luxury is the hedonism of age as partying is the hedonism of youth. But fun is about much more than hedonism. For a start, fun is a group activity. It is possible to have pleasure alone but fun is social and much of the satisfaction is in belonging to a group. The growing need for fun may be due to a new desire for group involvement (possibly as a result of growing dissatisfaction with individualism), and there certainly seems to be an increase in group activity of every kind. It is not so much that there are groups in order to enjoy fun as that there is fun in order to enjoy groups.

This is why so much contemporary fun – festivals, intoxicants, costuming, face and body painting, group dancing to rhythmic music – has recreated the elements of the earliest rituals of prehistory, which were discovered to encourage an ecstatic feeling of communal oneness. The mechanism is now known to be the release of endorphins, neurotransmitters which generate a sense of security and euphoria. Many activities produce an endorphin rush but the effect is intensified by activity in a group, and further intensified if the activity involves physical synchrony. The evolutionary anthropologist Robin Dunbar measured the endorphin release of single rowers and then of the same rowers using the same amount of energy as part of a boat crew, and found that synchronised rowing almost doubled the release. This would explain the increasing attraction of team games, group dancing and singing in choirs. And it turns out that military drill, not usually thought of as fun, produces a similar effect. So far as I know, there have been no comparative measures of endorphin release in different forms of synchronous activity but it would be further evidence of a prankster God if military drill proved to be the most fun of all. Maybe some entrepreneur should introduce square bashing as the new fun thing. All over the world parents of teenagers would rejoice.

Then there is the range of secondary fun functions. It can even be a quasi-religious provider of meaning. Or it can be the basis for a new form of snobbery, with the fun-rich flaunting their fun-wealth on social media in those millions of group photos with arms around shoulders, heads leaning in together, and faces wearing the fun smile, which is not just radiant but beatific. The beauty of this is that it is not yet recognised as snobbery.

Or fun can satisfy the contemporary desires for experience, authenticity, re-enchantment, play, comedy and transgression. The demand for experience is a consequence of increasing dissatisfaction with possessions (which is why the bookshops of the Western world are cluttered with books on decluttering). So holidays are less likely to centre on beating the Germans to the sun loungers and more likely to be a quest for adventure and the exotic (pony trekking in Nagorno-Karabakh) or adventure and danger, via extreme sports in remote locations - kiteboarding in Wadi-Lahami, active-volcano sledding on the slopes of Mount Yasur in the South Pacific island of Tanna, or canyoning (a combination of abseiling, rock climbing and white-water canoeing) in the Azores, lyrically described by Guardian Travel as ‘a place of wild rugged landscapes whipped by the ever-changing elements, where sailors swap tales of derring-do’.

These experiences also satisfy the needs for authenticity and re-enchantment, which are increasingly pressing as contemporary life comes to seem more and more inauthentic and disenchanting. Hence the attraction of activities connected to the remote, either in time or space and preferably both. Anything that can be described as wild is wildly exciting, especially wild places for wild camping and wild swimming, though the less adventurous can always settle for rewilding the garden, and those who would find even this too strenuous can go wild in an armchair with a plethora of wilderness films and books. And anything that can be described as hand-crafted is desirable, especially if the crafting hands are one’s own. So craft lessons are a new form of group fun, and craft festivals are a booming subset of the booming festival scene. The Goodlife Experience teaches campfire butchery and axe throwing, The Wilderness Festival revives ‘the ancient crafts of our wild forefathers’, such as basket weaving, The Shambala Festival has a blacksmithing workshop, The Green Scythe Fair promotes scything as a European mindfulness alternative to Tai Chi, and Spoonfest is entirely dedicated to the carving of wooden spoons, with spoonies coming from as far afield as Australia, Israel and the USA and a group of 200 meeting for communal carving.

This reverence for craft and need for meaningful group involvement explain the attraction of the term, ‘workshop’, used whenever possible to make abstract tasks seem physical and authentic. So there are policy workshops, meditation workshops, creative writing workshops, even philosophy workshops, and the term ‘tool’ is used for any kind of mental activity. The fortunate participants in a philosophy workshop will usually take home ‘a philosophy toolkit’.

The hunger for re-enchantment, and suspicion of a technical culture based on instrumental rationality and the tyranny of the project, are also behind the renewed interest in play, which is irrational and purposeless, a way of avoiding the own goal of always pursuing one’s own goals, an assertion that heaven is doing something just for the hell of it. Sport, festivals, dancing, costuming and sex play have all been growing in popularity for decades, and there is an increasingly explicit acknowledgement of play. The digital gaming industry has taken up play theory to justify gaming, and the self-help industry has adopted play as a replacement for the over-familiar mindfulness. Art is even more enthusiastically incorporating play - and especially childish, participative play - presenting, in museums and galleries, as serious works of art, ball pits, bouncy castles, aunt sallies, funhouse mirrors, helter skelters, slides, fairground rides, mazes and crazy golf. One of the most dramatic of such works was a life-size inflatable replica of Stonehenge, which toured the parks of the UK, encouraging adults as well as children to bounce on the site of pagan ritual, and was explained by the artist Jeremy Deller, winner of the Turner Prize and recipient of the Albert Medal of the Royal Society for the Encouragement of the Arts, as ‘a way to get reacquainted with ancient Britain with your shoes off’.

This play art is only one example of a return to the traditional play of childhood. In the USA there is a boom in summer camps for adults with all the childhood activities and games, and in the UK similar adult scout camps. Adult groups also meet to play Monopoly, Scrabble, even tag and hide and seek, and to construct with Meccano or Lego. But the most common form of play is dressing up, which has become an obsession. Everyone seems to want to dress up at every opportunity, with themed parties, themed stag and hen nights, themed corporate events, war games, murder mystery weekends, festivals that require costumes and giant cosplay conventions for the many who wish to dress as comic book or gaming characters.

Why this mania for fancy dress? One hypothesis is that dressing up manages to reconcile, if only briefly, several strong and often contradictory contemporary urges. Fancy dress is usually for social occasions, and so combines the need to stand out as an individual with the need to be accepted by, and belong to, a group. And since the costume is a personal choice but immediately recognisable as a familiar character, type or thing, it combines the desire to express a unique personal identity with the opposite desire to abandon this exhausting task for the ease of a ready-made identity as a Venetian noble, a zombie, a pirate, a chicken, or, possibly most reassuring, a banana. It also offers a form of childish play to those who are no longer children, a way to reject convention without giving offence, and above all a way to become an actor without having to act.

Dressing up can also satisfy the need for comedy and transgression, which is one reason why, in cosplay, zombies are one of the most popular types, and the Joker, Batman’s demonic foe, is one of the most popular individuals. And the need for stronger transgression is behind the growth in swinger clubs and the extraordinary popularity of BDSM. In an age that reveres freedom, domination and submission become new taboos, and BDSM gets an erotic charge from re-enacting the roles most discredited by modern society – those of master and slave. The pursuit of freedom has had many unforeseen consequences but one of the strangest must be that it has made bondage exciting.

Best of all is fun which combines functions – comedy and transgression, authenticity and re-enchantment, synchrony and play. This accounts for the startling success of the World Naked Bike Ride, an annual event where thousands of naked people ride bicycles through hundreds of cities and towns in different continents. Why would anyone want to strip and ride a bicycle through a city? How did this ever get started? Why has it spread round the world? One answer is that it combines all the fun functions – the physical synchrony of riding in a group, the transgression of nudity, the comedy and playfulness of nudity on a bike, as well as the neo-pagan re-enchantment of celebrating the human body and the political protest of challenging the evil automobile. And even nudity provides opportunities for dressing up - in wacky hats, non-concealing accessories (feather boas are especially popular), face and body painting and on bare backs slogans like LESS GAS AND MORE ASS.

Even the most adamant despiser of fun would surely be moved by a tsunami of bare flesh pouring down a city street on every kind of bicycle, and also unicycles, tricycles, tandems, three- and four-seaters and rickshaws, displaying every size, colour, shape, age and condition of body, with every imperfection, surplus and deficit - shrimp dicks and jellyfish tits, whale-blubber bellies and asses like acid-corroded reefs. This must be how human life looks to God – an endless river of flesh, ridiculous, vulnerable, ageing, flawed, flowing towards its dissolution in the unforgiving sea. But how blithe, how wanton, how glad the doomed flesh! This river is bound for oblivion but can make its own beguiling music, frolic, sparkle, dance and laugh along the way.