Better art critics than I have had trouble defining Fluxus. Even in a field as cluttered with vagaries as the history of the post-war avant-garde art movement, it commands an especially ungraspable corner. It’s like an eel in the water or the insight from a haiku: sometimes you see it clearly and other times you can’t see it at all. Yet this elusiveness is usually, in my experience, the mark of something worthwhile in art. The movements you need to be suspicious of are the ones that say it all with their first breath. Let me put it another way: who is the better actress, Jessica Alba or Meryl Streep?

One thing we can all agree on is that Fluxus was important. The artists it helped to unveil — Joseph Beuys, Yoko Ono, Nam June Paik — are sizeable post-war figures. People who counted were drawn to Fluxus. Not only did it redefine art, it did so in hugely influential ways. For a first sense of that impact, don’t even bother going into the lively Fluxus exhibition that has now arrived at Baltic, in Gateshead, but linger instead in the gallery shop and look around for things to give people at Christmas.

See the little fold-up snow scenes and the dinky origami gingerbread houses from the Museum of Modern Art in New York? Those were influenced by Fluxus. See the range of dotty alternative Christmas cards with amusing David Shrigley messages that nearly make sense? Fluxus. Everything in here that can be sent in an envelope or folded at home, every off-centre social insight and faux-naive cultural opinion, even the sense of clutter, the sheer range of disposable knick-knacks, was preceded by Fluxus. Indeed, take the rebellious intent out of Fluxus and you’ve got the Baltic knick-knack shop.

So, what was it? A 1960s version of Dada would be the pat reply, although that begs the question: what was Dada? Which is even harder to answer. Prior to this event, I was content to accept the usual dictionary definition that Fluxus was an anti-art art movement that originated in New York in the early 1960s and soon became international. How can an art movement be anti-art, you may be thinking? Fluxus was anti-art in the sense that it attacked the old ways of being an artist. It was against museums, galleries, dealers, résumés, retrospectives, corporate commissions, the whole shebang. According to tortuous Fluxus thinking, commercial success was something to be avoided rather than striven for.

Instead of producing expensively autographed trophy objects that only the rich could buy, Fluxus artists set out to mass-produce witty, ephemeral think-art that everyone could afford and that carried subversive messages out of the gallery system and into your daily life. Walking into this Fluxus show is indeed like walking into the gallery shop. You’re greeted by busy display cases filled with small things, printed and folded, gathered in boxes, labelled and mounted. There’s a jokiness afoot as well, which you recognise from the default tone of modern advertising. Read anything in here and the chances are that it will a) need to be read again and b) make you smile.

For these same democratic reasons, Fluxus pioneered outdoor happenings and street events, particularly of a musical bent. If a cello player stripped naked to play Berio, or someone began wrapping their violin in sticky tape at the climax of a Ligeti composition, they were probably doing it for Fluxus reasons. Baltic’s reading of the Fluxus tea leaves, however, is drawn exclusively from the famous holdings of the Gilbert and Lila Silverman collection in Detroit; and, rather than present the entire movement as a floaty international art tendency shared by many, which is what I was expecting, the show seeks instead to define it as the specific aesthetic creation of one man: the renegade Lithuanian uber-nerd George Maciunas.

Maciunas arrived in New York in 1948 with a dodgy past and a scrambled sense of self. Born in Kaunas in 1931, to a father who worked for the German Siemens company (and who, ingloriously, continued to work for them long after the war started), Maciunas lived most of his life with his mother and married only a few months before his death in 1978.

A classic self-absorbed mummy’s boy, suffering, I would suggest, from some form of OCD, he should have been a librarian or a stamp collector: that is where his talents for filing and collating usually lead people. History, however, had infected him with a revolutionary gene, so he became the chief organiser of Fluxus instead.

The show’s full title is George Maciunas: The Dream of Fluxus, and its overwhelming ambition is to present Fluxus as his personal achievement. The catalogue refers to him habitually as “the Chairman”, and everything we see here — the boxes filled with wacky objects, the movies of people’s bottoms, the typed instructions to turn on the radio and turn it off again at the first sound, the all-white chess sets, the street theatre — was organised by him. Maciunas it was who invented the name Fluxus, with its promise of constant change and its hints of biological discharge. Trained as an architect, he assembled the Fluxus boxes himself, by hand, and designed all the movement’s typography.

The first official Fluxus show was in Maciunas’s gallery in 1961, and when nobody noticed it, he fled the country to escape his creditors. He ended up working as a graphic designer for the US army in Germany, where he continued to organise Fluxus events and promote them on army-issue typewriters, using army stamps and army petrol coupons. In Germany, he launched the Fluxus Festival, and his methods certainly struck a German chord. Much of what Fluxus produced was the result of his kind of feral creativity, which depended on scavenging. The artist I would have named before this show as the most important Fluxus artist of all, Joseph Beuys, encountered Maciunas round about now and learnt many things from him.

So, Fluxus undoubtedly owes Maciunas a lot. But does it owe him everything, as this display implies? Beuys, for instance, isn’t even in the show. And, although Yoko Ono and Nam June Paik are included, it is as beneficiaries of Maciunas’s efforts on their behalf, rather than as co-conspirators. Of course, one of the telltale signs of an active avant-garde art movement is the vicious infighting that accompanies it, and the subsequent squabbling over credit. Fluxus was no different.

The Baltic show is the equivalent of a surrealism exhibition that focuses exclusively on André Breton and ignores Dali, Magritte and Man Ray. So intent are the organisers on purifying the movement and presenting Maciunas as its presiding genius, a sense of its greater achievements has been lost. What I consider the classic Fluxus event isn’t mentioned either. I’m thinking of John and Yoko’s bed-in of 1969. Their ambition was to protest about the war in Vietnam, but instead of marching on the American embassy in Grosvenor Square, they sat in bed in a hotel in Montreal for a week and sang Hare Krishna tunes. And the whole world noted them doing it. That Christmas, the world’s in-trays were flooded with sweet printed messages saying: “War is over! If you want it. Happy Christmas from John and Yoko.” That, surely, was Fluxus at its best.

George Maciunas: The Dream of Fluxus is at Baltic, Gateshead, until February 15

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