The wild spirit of an all-creating God seems to blow through every dab and shape of colour at the Matisse show at Tate Modern

Saw God last week. Not in a sunset or a rainbow, not on Mount Sinai or Uluru, not in Chartres Cathedral or on Glastonbury Tor, and certainly not on the road to Damascus, where these days one is more likely to encounter the devil. No, I saw God at Tate Modern.

If Nicholas Serota, the director of the whole Tate caboodle, thinks I’m talking about him, well he’s not a million miles wide of the mark. It was thanks to his expansive curating, anyway, that I had my big experience, between coffee and a full English breakfast with a 10 per cent discount for Tate members.

It is, of course, the current sell-out Henri Matisse exhibition I’m talking about – Matisse himself infirm and chair-bound, but the art alive as though the wild spirit of an all-creating God blows through every dab and shape of colour. The work is so exceptionally alive, in fact, you half wonder whether the infirmity is essential to it. What we can say for sure, after this, is that there’s no better route to spiritual beauty than through an apprehension of mortality.

Which might have been what Matisse was getting at in his famous conversation with Sister Jacques-Marie, the Dominican nun who was closely involved with him in his designs for the Chapel of the Rosary at Vence. Dismayed to hear Matisse talk of making the chapel for his own pleasure, Sister Jacques-Marie reminded him that he had once said he was making it for Almighty God. “Yes, but that God is me,” he told her.

Matisse and the nun were very close – close enough to share a joke. Rumour had it that she posed nude for him. (Who wouldn’t pose nude for Matisse?) We must assume, whether that’s true or false, that they would on more than one occasion have discussed the sacred and the profane. And to an artist it is profane to talk of an Almighty God who exists outside the art. “Yes, but that God is me” is another way of insisting that divinity is in the work or nowhere.

Picasso found it hard to forgive Matisse for working on a chapel. He missed the point. Even the stained glass windows have no religiosity about them. They celebrate the wonders of the visible world – never so blindingly visible until made so by an artist.

No one should miss this extraordinary exhibition. Ignore the critical unanimity of enthusiasm. I know, I know, agreement kills. Especially when those doing the agreeing are art critics. But this time, reader, miracle of miracles, they are right. And what is more they are right in the name of art’s exhilarating example – the happiness of creation, fecundity, verve and vigour, colour – rather than those footling ironies to which, in the name of conceptualism (the unmade-bed of the embryo artist’s mind), Tate Modern has too often granted indulgence.

We have been rude about Tate Modern in this column. A palace of sterility we have called it. But we are happy now to take all that back. Had it never done better than this show, and were it never to do better again, its existence is now justified.

And how clever of the curators to have eschewed cleverness – that curse of the contemporary – and entitled the exhibition simply Matisse: The Cut-Outs, with its suggestions of kids messing about at school with scissors and coloured paper. Was ever a show less dauntingly described? And as it is described, so it proceeds, 14 bursting rooms of such exuberant creation that you discover you are wandering in and out of them – for this is a show to dawdle without aforethought through – in an unaccustomed mood, an unaccustomed expression on your face. Is that a smile? I would not want to make this the once and forever criterion of a good art show, but never have I seen so many people in an art gallery looking happy.

Nor do I want to make it sound as though we were all in the grip of some joyous freedom from exactingness. The greatest art is that of concealing art, and the intellectual life is never better served than when intellectuals speak their profundities in the language of men talking to other men. No artist was ever not an intellectual to some degree, and we’d be fools to suppose that the lightness and immediacy that Matisse achieved with his cut-outs was a triumph of spontaneous or accidental mindlessness. But he was an artist of the greatest tact, and it is artistic tact to hide the means by which you come by your effects and the labours of technique and thought that enable you at last to produce work that seems labour-free.

You can look for hours at a time at those famous blue cut-out nudes, which somehow are as much sculpted as scissored, as though a flat piece of paper has a third dimension that only a great artist can find in it; yet no matter how long you look you will not discover how this is achieved, how the paper folds back in time as well as space upon itself, and how even the still spaces between the shapes possess the dynamism of movement and change.

Whatever mischief Matisse intended by saying “God is me”, one cannot deny the mystery of creation before these works. The Judaeo-Christian God shaped man from clay, breathed into his nostrils and then expected him to do as he was told. Being cut into life by Matisse’s scissors for no other purpose than to express natural vitality and enjoy the simple fact of being strikes me as preferable.

“I have always wished my works to have the lightness and joyousness of a springtime which never lets anyone suspect the labours it has cost,” he wrote in 1948. But he worried that a young painter, eager for fame, would see only apparent facility and negligence and use that as an excuse to skip the labour. The inspiring paradox at the heart of this magnificent show is that you have to toil to achieve lightness and that it’s only when you are autumnal that you can create the joyousness of springtime. Ripeness is all.

Whatever mischief Matisse intended, one cannot deny the mystery of creation before these works