There are grounds for suspicion, after all. Pollock's peculiar greatness is partly a historical thing. The conditions were propitious. Here was the United States: just won the war, richest nation, top of the free world, supremely confident. Whatever artistic talent it produced was going to benefit from this dominance; to be given - if remotely possible - the status of world leader.
Within US culture there was a role waiting, too. Great American Artist: position vacant. There'd been the Great American Novel (Melville) and Poem (Whitman) and Music (Jazz). But in the visual arts, there'd been no body of work that convincingly broke free or ahead of the European tradition. The frontier of modern art was still Paris, not New York.
You don't have to deal in active conspiracy theories here (even though "The CIA invented Abstract Expressionism" is a perfect charmer). Circumstances were such that the next big thing in American art was likely to get very big indeed. What's more, Pollock's work fitted the bill so well. Its temperament was free, raw, expansive, commanding, and it had pioneer spirit. But also it was - really was - highly original.
The novelty of the paintings Pollock made, in a barn out the back of his Long Island home, was partly in how they looked, and partly in how they were done. Their compositions were "overall": they had no image, of course, and no governing design or obvious focal points. They abandoned handiwork. Dripping his paint from sticks and old brushes, Pollock substituted gravity for touch. The relationship between painter and painting was changed. The canvas was laid on the floor. It became an arena for action. What developed on the surface wasn't so much a picture as a record of bodily movements.
That's the textbook story, so to speak. But to praise an art, 50 years on, in terms of its originality as such, isn't quite going to work. Originality is a relay race that nobody wins. One breakthrough gives way to another. Pollock's influence has been wide. For instance, the performance side of his action painting led into performance art. But that's hardly what's good about Pollock's painting.
And what we see in the classic Pollock paintings - works such as Lavender Mist and One - is an ambition that exceeds mere innovation. They're astonishing spectacles, swarming and exploding before our eyes. They're paintings that want to be more than paintings; that want to slip the surly bonds of art. He didn't want just to be ahead of the game. He wanted out. For a short while, he was.
What we're talking about, though, is a short while. A retrospective prompts an obvious question. Is it going to be a long build-up to a final breakthrough, rich in anticipations and approaches, but with all the earlier work only interesting for what it promises? Or is it going to be a full, if brief, career?
It was clearly a struggle. The Pollock myth emphasises the wild, violent, drunken, boho outsider. But the progress of this exhibition suggests another kind of individualism: a good, work-ethical, rags-to-riches story. Talent- wise, Pollock started poor. The earliest paintings are turbulent art-school effusions, and the turbulence continues as Pollock gets heavily influenced by European modern art (Picasso, Mir, Andre Masson), and goes on being influenced - and figurative - for quite a time.
There's a lot of personal mythology stuff: jagged, writhing, doomy confections of archetype and hieroglyph (he was into Jung). But among them, one or two paintings stand out. Stenographic Figure, done when Pollock was 30, is a high-spirited, light-hearted image of loopy critters. It was an important picture for Pollock's career. It caught Mondrian's eye, resulting in Peggy Guggenheim's patronage. But in itself, it's a one-off. It shows a side to Pollock normally hard to imagine: a sense of humour. It might have led anywhere.
Not that the other work of the early Forties shows anything like a clear trajectory. It's all over the place. There are some works which, in hindsight, seem to look ahead - such as the huge, long painting called Mural (1943) he did for Guggenheim. I don't myself get a big kick out of this acknowledged milestone, but its strongly rhythmic, highly elaborated calligraphy of dancing stick men can be seen as pointing to an overall abstraction. And Eyes in the Heat (1946), a very exciting field of swirling energies, with the paint delivered straight from the tube, seems on the very brink. But at the same time, there are pictures that declare he'll never get Picasso out of his system.
And then the dripping starts. It starts uncertainly. And though within a year or two it's reached perfection, these first drip-pictures, very hit-and-miss, let you see what this perfection involved - and see, too, what the work looked like to many of its first beholders. It looked like a mess, or again like a pretty mess. Quite often with the early ones, you really do get wilful mess-making, and it's not interesting. Quite often, too, you get a pleasingly distressed surface-texture. And both these impressions are worth holding onto.
Pollock sometimes wondered if what he was doing now was art. His critics, pro and anti, have sometimes thought not. The antis saw doodles and decor - "apocalyptic wallpaper" was the great put-down. The pros saw the pure, unmediated expressions of body or soul; a painting made in a trance state, with Pollock's unconscious or impulses marked down on the canvas. Obviously, this was partly what Pollock wanted. He wanted a spontaneous painting that by-passed the turgid symbolism of his earlier psycho-dramas and came straight from the deep psyche. He wanted pictures that - like some decoration - looked unmade and unauthored, as if they had just developed of themselves. But the paradox of his achievement is that these things could only be done with a lot of artistry.
Pollock's act was a careful balancing act; a matter of holding things in tension, fine-tuning so as to keep all possibilities open. The classic paintings have multiple intimations, none of which is quite suppressed, none of which definitely arrives. There are - despite the "over all" talk - hints of an underlying structure, perhaps something quasi-figurative and deeply buried in all the business. There are hints, too, of infinitely complex patterning. There are hints of complete chaos and randomness. There's finally a strong entropic tendency towards an absolutely inert homogeneity. And all these aspects shift one into another.
The result is work that's untraceable and ungraspable. It offers inexhaustible interest to the eye. It can be contemplated endlessly. It always offers something new. And if you're content for that to be what painting does, you can hardly ask for more. If, on the other hand, you want to give meaning to this intensely absorbing experience, you're taking a risky step. The great Pollocks have an unlimited appetite for significance. They gobble it up and ask for more. Every big feeling in the world can attach itself to them. It's another thing that made them such excellent candidates for greatness.
These paintings last, not for their innovations, but because they still stick in art's craw. Pollock's most memorable saying was his reply to being asked, why he didn't work more from nature: "I am nature." It needn't have been a megalomaniac boast. It was no more than the literal, partial truth. Who isn't? His achievement was to turn art into natural history, to make human artefacts that have the fascination of natural phenomena; blank wonders, endlessly interpretable.
It has a limit. And having reached it, Pollock rather impressively stopped - treated it as an aberration almost. At the start of the Fifties, he (so to speak) re-wound seven years, went back to much the same kinds of picture he was doing before the drip-work started (some figurative, some less so), fell under the same old influences, did some more very interesting one-offs such as The Deep, got too drunk to paint at all, and crashed his car. There are many rather spurious romantic tendencies in Pollock's art and myth, but this late falling off is a vindication of them, and it baffles posterity's calm judgements. Briefly he had been visited.