'Beginning with a flag that has no space around it, that has the same size as the painting, we see that it is not a painting of a flag. The roles are reversed: beginning with the flag, a painting was made. Beginning, that is, with structure, the division of the whole into parts corresponding to the parts of a flag, a painting was made which both obscures and clarifies the underlying structure. A precedent is in poetry, the sonnet: by means of language, caesurae, iambic pentameter, license and rhymes to obscure and clarify the grand division of the fourteen lines into eight and six.'

"In 1957-58 Johns immersed himself in greyness in a series of encaustic paintings such as Grey Rectangles and The, where the surface is covered all over by slow, gentle, rather haphazard marks contrasting in tone only as far as they must be to be separable and looking as if they might have been made when half-asleep of half-awake or drugged. Their formlessness is corrected by the insertion into the surface of simple geometric shapes placed symmetrically or by a one-word inscription painted in capital letters of a classical mould. Both devices evoke the tomb, and this matches the elegiac atmosphere engendered by the grey. One of the pictures is inscribed and also entitled Tennyson. Several have a Tennysonian mood:

The woods decay, the woods decay and fall,
The vapours weep their burthen to the ground ...

"That distinction between saying something and being something corresponds precisely to Wittgenstein's distinction between what can be said and what shows itself, and the point about art is that it shows rather than says. Johns's sense of the distinction between saying and showing produced a memorable declaration: 'When you begin to work with the idea of suggesting, say, a particular psychological state of affairs, you have eliminated so much from the process of painting that you make an artificial statement which is, I think, not desirable. I think one has to work with everything and accept the kind of statement which results as unavoidable, or as a helpless situation. I think that most art which begins to make a statement fails to make a statement because the methods used are too schematic or too artificial. I think that one wants from painting a sense of life. The final suggestion, the final statement, has to be not a deliberate statement but a helpless statement.'

"Shortly after the recording ended, he added: 'To be an artist you have to give up everything, including the desire to be a good artist.'

"From the beginning Johns's art was concerned with concentrating attention on visual nuances much as Cage's music concentrates attention on aural nuances, and with Johns as with Cage that attentiveness generates a particular poignancy. Everything depended on the slightest inflections of the paint or wax or the pencil or charcoal or wash, which meant that the marks had to be on a smaller scale than those which were commonly current. Hence the affinity of the marks in the paintings to those of Cézanne, and of the marks in the drawings to those of Seurat and occasionally of Van Gogh's landscapes (as in Flag, 1958, in Leo Castelli's collection). Johns achieves something of Van Gogh's total translation of life into a script or a complex of scripts.

"I said: 'I take it that when you're making art you're often saying to yourself 'It would be interesting to see that."' He answered: 'Or "it would be interesting to do that", which is not the same.'

"Commands to himself to do something often occur in his sketchbook notes. ('Make something, a kind of object, which as it changes or falls apart (dies as it were) or increases in its parts (grows as it were) offers no clue as to what its state or form or nature was at any previous time.') He is one who has always been driven to do things by working on some surface or another with some tool or object or another and/or some medium or another. ('Take a skull. Cover it with paint. Rub it against canvas. Skull against canvas.') While a famously philosophic artist, whose work was a key point of departure for conceptual art, he is anything but a conceptual artist. Just look at a catalogue list of some of his drawings and see how many different techniques and media and original combinations of them are there. Johns is a maker.

"It may be that focusing on the making diminishes thinking about what one intends the work to mean, leaves the unconscious with room in which to operate, allows meaning to accrue without interference. As Cézanne said: '. . . if I get at all distracted, if my concentration lapses, above all, if I do too much interpreting ... if I start thinking while I'm painting, if I intervene, then crash! bang! the whole damn thing falls apart.'

"A recent book has made public the results of aggressive research into Johns's life from which it can be concluded that he had a lonely and painful childhood. John Cage's 1964 text included one deadpan biographical paragraph which made it clear without saying so that Johns had had a childhood of a sort that badly needs redeeming later.

"Johns's recent work has made public certain documents relating to his childhood by incorporating into his pictures family photographs and the ground plan of his grandfather's house where he lived for some years. However, there is nothing in the pictures themselves that conveys the personal significance of such material. Johns's work has already contained from the outset far clearer references to his first years inasmuch as so many of his initial themes - flags, targets, numbers, letters, maps, rulers, and a later subject, the puzzle-picture - and then the use of certain techniques - such as rubbing, finger-painting and tracing - belong to the schoolroom and to the nursery; in the light of that paragraph of Cage's, John's activity as an artist has long seemed to have centred on retrieving and resolving his childhood. Nor does he deny it: in 1978 he told an interviewer: 'I certainly believe that everything I do is attached to my childhood . . .' And in 1963, asked why he had done paintings to which he affixed a wire with a fork clamped on, he answered: 'I heard as a child that a man had repaired an aeroplane with chewing gum.'

"There's a recent work that goes farther into the past: a series - perhaps a triptych - of untitled paintings each with roughly the same composition and a monochromatic field: from left to right, an oil with a purple ground of 1991-94, an oil with a white ground of 1991; an encaustic with an ochre ground of 1991. The ground is almost bare, with a few emblems scattered around a picture of a picture attached with trompe l'eoil nails. It is a found image, a drawing by a schizophrenic orphaned young girl published by Bruno Bettelheim as The Baby Drinking the Mother's Milk from the Breast. Seeing the triptych (or series) several times without knowing or guessing anything about the drawing, I constantly perceived the bland and immaculate white ground as an ideal image of food - a miraculously smooth and succulent area of icing or ice-cream which was waiting to be licked and licked away. The orphan's drawing and the edible whiteness add up to a symbol of the sucking infant's longing for perfect nourishment; the surrounding emblems include a mouth and two eyes that are also breasts with prominent nipples. Each breast is fenced off by a set of nails with their points outwards.

"Assuming that Johns's Flag, 1954, was a classic case of a work of art as epigram, and given that an epigram has to be surprising, simple, witty, subversive, elegant and at best deeply serious, it might be amusing to list some of its predecessors in the first half of the century.

Matisse's The Red Studio, 1911
Duchamp's Bicycle Wheel, 1913
Picasso's Absinthe Glass, 1914
Malevich's White on White, 1918
Man Ray's Gift, 1921
Magritte's The Treachery of Images, 1929
Meret Oppenheim's Fur Breakfast, 1936
Picasso's Bull's Head, 1942
Duchamp's Female Fig Leaf, 1950

"As we would expect: first, most of the works are three-dimensional; second, most of them are dada or surrealist. The only pieces which are neither are The Red Studio, White on White and Flag. Each of these is a conceit on the attributes of painting. The inclusion of a structure as complex as the Matisse may be thought questionable if an epigram has to be simple. But the conceit is simple.

"The conceit in Flag is to represent an object in such a way that its edges coincide with the edges of the canvas. The space between the object and the spectator is squeezed out of existence. To some extent this gambit was anticipated by Magritte, an artist much admired by Johns, in his Representation of 1937 - and it was certainly a case of anticipation rather than influence because by 1954 the picture had neither been exhibited outside Brussels nor been reproduced. It is a close-up of a woman's pelvis which was presented on a rectangular canvas until Magritte took a pair of scissors and shaped the canvas to follow the outline of the pelvis and then had a frame made to fit. In the realisation, Magritte aimed at illusion and therefore made his paint invisible so that it could look like flesh and skin, whereas Johns, of course, makes the paint more or less as visible as the image.

"The story is 'I dreamt one night that I painted the flag of America. The next day I did it.' This sounds like an episode in the life of a biblical prophet. At least one great painter of our time, Francis Bacon, seems to have seen himself as that: 'I don't think I'm gifted; I just think I'm receptive ... I think I have this peculiar kind of sensibility as a painter where things are handed to me and I just use them . . . I suppose I'm lucky in that images just drop in as if they were handed down to me.' Johns might well have felt that images were being handed down to him not only when he first did the flag in 1954 but also when he first did targets and the figure 5 in 1955 and alphabets in 1956 and numbers and all-over grey brushstrokes in 1957 and sculpmetal bulbs and flashlights in 1958 and 0 through 9 and polychromatic explosions with superimposed stencilled words in 1959 and painted ale cans in 1960 and the map of the USA in 1961 and the Skin drawings in 1962. It was as if for those nine years Johns was in a perpetual state of grace. And as if a voice from above then said: 'Jasper, we've done enough for you; you're on your own now.' Suddenly the boy genius had to become a man. Hitherto the struggle had been confined to the realisation of the image; from now on Johns was going to have to hunt the image down. It is true that the legendary passing encounters while out on drives with the prototypes of the pavingstones and the cross-hatching are about finds rather than hunts - but they were still finds, not revelations. (By the way, it was in 1963 that Johns first consented to give a serious interview, as if he were now responsible for what he did.)

"The crisis in Johns's history came during the realisation of the Diver drawing measuring about seven feet by six - his biggest and best work on paper. He started it in 1962 and before completing it the following year interrupted work on it to execute in November-December the Diver painting. This too was his biggest piece in its medium yet. The format here is horizontal, slightly higher than the drawing and more than twice as wide. Compositionally it's a five-part polyptych, and it's the centre panel that corresponds with the drawing. And whereas the drawing has the same marvellous fusion of the surprising and the inevitable as the flags and the targets and the alphabets and the maps, the painting seems inconclusive. It was the first of several large horizontal canvases on which Johns was manifestly reaching to become a different kind of artist: According to What, 1964, Studio, 1964, Untitled, 1964-65 (Stedelijk, Amsterdam), Eddingsville, 1965, Studio II, 1966, Harlem Light, 1967. What seem to me the totally resolved works among these were not included in Kirk Varnedoe's retrospective at the Modern - Harlem Light and the first Studio, its explosive trompe l'oeil sunburst of grey on grey next to that great white slanted door an affirmation that Johns, having worked until 1962 on the scale of de Kooning and Guston, also had it in him to perform on the scale of Pollock and Newman. However, he has not often seemed at home when working on fourteen-footers and upwards.

"One arresting thing about the Diver is how the scrawls and scribbles lie on the smooth surface of the pair of abutting panels, creating a beautiful tension between the freedom of the artist's gestures and the resistance of that hard dense wooden ground - a ground which in reality is not wood at all but paper mounted on canvas. The band down the middle which is partly lighter in tone is certainly meant to be read as a wooden plank. It is also meant, from the footprints at the top, to represent a diving board. Matching circular vectors traversing the bottom corners indicate the sweep of the diver's arms. Starting at the foot of the vertical band a pair of stylised arms with hands at each end - they look like tribal ritual objects - rise at an angle such that the top pair of the hands is just outside the edges of the band. The lower pair of hands is clearly entering the water. The slightly outstretched upper pair of hands could be a reference to the position of the arms at the beginning of a dive but could also suggest someone in the water crying out for help; they have been interpreted as an allusion to one account of Hart Crane's suicidal dive into the sea. Taken in conjunction with that central vertical band, the arms also hint at a crucifixion. Speculation is encouraged by the work's glowing muted luminosity, and any mystery as to the iconography is far outweighed by the mystery and the drama of the golden and brown tenebroso lighting and the play of free, impassioned drawing within a stark structure. It's as if Rembrandt had been at work on a Barnett Newman.

"In the retrospective the work was hung near another very freely handled piece similar in size, Watchman, the painting in oils with a wax-cast of a leg sitting on a real chair, inverted, attached in the top right corner. It was made in 1964, while the artist was in Japan, a sombre work that has always seemed to me the finest of those pieces Johns realised at around this time which, basically through long broad brushstrokes and dribbles of paint, evoke Rauschenberg. Whereas Diver, while expressly being about a descent, is also suggestive of contrary movement, Watchman is a conclusive image of descent. If Diver looks like a Newman done over by Rembrandt, Watchman looks like a Rembrandt done over by Rauschenberg. That is what it looks like; what it is is a Rembrandt done over by Johns. There are so many correspondences in the lighting and the composition - down to the way the chair replaces the Cross and the ladder - that Watchman is clearly, knowingly or not - Johns tells me not - a remake of the Descent from the Cross in the Hermitage.

"It is not surprising that the standard critical assessment of Johns's career resembles that of de Chirico's - that each had a marvellous beginning which made him a major influence while he himself was declining well before he was forty. It is not surprising, because Johns had done everything to activate America's powerful drive to sacrifice her gods while the memory of their apotheosis is still fresh. He has played a double game. On the one hand he has toyed obsessively with the motifs that made him famous, and here he has been subject to the law of diminishing returns. A parade of his Flags, say, shows that those reallsed after the first ten years have mostly been less vibrant or coarser, and this has given good reason to perceive him as a typically fading lyric poet. At the same time he has constantly explored new thematic material. As I see it, these explorations have produced a continuing self-renewal, but the view is widely held that they have been arcane, cerebral and aethetically dry. They certainly tend to seem like that when first encountered, but there can be an efficacious remedy, which is to follow Wittgenstein's advice: 'Don't think. Look.' What is sure is that the very extent of John's bipartite production has not helped his cause. The more an artist makes, the more targets he erects. And even a faithful supporter may feel that there are many individual pieces for which it is difficult to see a raison d'être transcending Johns's compulsion to experiment.

"On the other hand, the retrospective showed a rare absence of those fallow periods - fallow in quality - that normally appear in retrospectives, even of major masters. The nearest thing to such a period here was the second half of the Sixties, but these years still produced Voice and Voice 2. Here for once was a retrospective that did not diminish the artist, though I wonder whether the selection could not have done more to convert unbelievers by being less inclusive. The message for me after a dozen visits was that in the pantheon of painters of the second half of the century it could be Johns who sitteth on the right hand of Newman the Father Almighty. If he does, the iconography is rather apt: Newman's art is immaculate and in charge; Johns's bears the scars of recurrent self-crucifixion.

"In the latter part of the retrospective Varnedoe confronted the visitor with a wall bearing a juxtaposition of two 1982 encaustic paintings, one of upright, one of landscape format, both with hanging casts of forearms coloured in harlequin patches - one, In the Studio, a dazzling image of daylight; the other, Perilous Night, the most turgid thing Johns has ever done, its left side more crazed than the wildest excesses of Albert Pinkham Ryder. They complement each other as if they ought never to be separated. In both of them the forearms convey conflicting intimations of inert objects hanging useless and of living forms lightly touching the wall with their fingertips - in Perilous Night so living that as I look I sometimes experience the hallucination that those three arms hanging side by side have detached themselves from the wall and started behaving like mythical snakes.

"Johns's tellingly emotive use of casts from parts of the body above all, here and in the assorted fragments pinned to criss-crossing lengths of wood in the sixteen-foot-wide Untitled, 1972, at the Ludwig Museum, Cologne - shows how resourcefully he exploits the fact that low relief is the most poignant form of visual art there is. There's a further dimension in the polychromed fragments in Untitled, 1972, fragments that look as if they've been torn away from bodies. They have the lacerating impact that late medieval German polychromed sculpture can have. They are so scary that the wing-nuts and bolts in the carpentry suddenly seem to be thumb-screws. I say this because the atmosphere of the scene suggests that the damage to a body has been inflicted in a martyrdom rather than a battle. This harrowing image is made Johnsian, redeemed from Expressionism, through the alienating visual conceits by which the islands of torn-out flesh are echoed in the flagstones of the two middle panels and both the flagstones and the criss-crossed pieces of wood are echoed in the patches of cross-hatching in the left-hand panel.

"In the Studio is curiously Beuysian in atmosphere (see Show your Wound, for example), what with its use of varied repetition and its haunting sparseness. What is especially Johnsian about it is how it concentrates attention on nuances in what we are looking at - for example, the differences in their angles to the wall of the yardstick, the cast of a forearm and the pinned sheet of paper bearing a life-size drawing of a forearm. The other variation presented, in the upper and lower versions of a cross-hatch picture pinned to the wall, is between an intact work and one melting away as we look. That melting process appears again in the work which for me is Johns's most amazing piece of the late Eighties, The Bath, 1988. 1 do not know why this picture moves me so profoundly. Perhaps it is about making Beauty and the Beast coalesce. It brings together two of the most gruesome of Johns's reiterated quotations, in the background a monstrous detail from Grünewald's Temptation of St Anthony, and pinned to the wall Picasso's grotesque Woman in Straw Hat of 1936, treating them in a palette which could have been borrowed from Velázquez's Rokeby Venus. And then it incorporates the melting process that makes the Picasso head look as if its nose is dissolving into snot. At the same time, it has the lovely melancholy lyricism of a Medardo Rosso wax head of a child.

"Is it because Duchamp has been very fashionable in America while Braque has been underestimated that Johns's affinities to Duchamp have been magnified while those to Braque have gone unnoticed? Of course Duchamp inspired him in the Sixties even more than he did most of the leading artists of Johns's generation. And of course Duchamp and Johns became rather friendly: they both lived mainly in New York, Duchamp was a mythical figure yet not difficult to meet kindly and courteously accessible to younger people who had a real interest in knowing him - and it would have been astonishing if he and Johns had not got on extremely well, seeing that both of them had a brilliant, elegant, mordant intelligence and liked to laugh. But it is not certain that Johns learned a lot from Duchamp that he would not have learned from Cage, and they were very different characters despite their shared penchant for taking pleasure in arousing but not satisfying curiosity. Duchamp was more relaxed and dandyish, and while secretive in many ways, did not have Johns's pudeur. Johns said the early Nineties: 'He has qualifies that are foreign to my nature. I think he's more cheerful in his scepticism and more detached.' But even in 1965, at the height of Johns's involvement with Duchamp's thinking, he made it clear what a gulf there was between them when Walter Hopps alluded to Duchamp's professed unconcern with how his artworks looked by comparison with their idea-carrying qualities and asked Johns whether he had ever worked from such a standpoint. 'My idea', said Johns, 'has always been that in painting the way ideas are conveyed is through the way it looks and I see no way to avoid that, and I don't think Duchamp can either.' This links up with the most obvious and perhaps the profoundest difference between them as artists: that Duchamp made as little art as possible and Johns is manifestly addicted to the manual labour of art.

"As to influence of particular works on particular works, this seems to have been most active in a few minor pieces. In the realm of major works there's a consensus that, when Johns started in 1963-64 to paint large complex horizontal pictures like According to What, his paradigm was Duchamp's Tu'm of 1918. But on what grounds? Just two or three elements of the iconography. The style has nothing to do with Johns: it is illusionistic; it gives no sense of the presence of the picture plane; the matiére is transparent. These works by Johns may play games with the addition of real objects to a painted canvas, but their central preoccupation is the paint on the canvas, worked, layered, varied in texture, self-assertive.

"It seems to me that, knowingly or not, Johns's more complex compositions since the mid-1960s have had a crucial and somewhat increasing resemblance to some of Braque's late Studios, the series of eight mostly large canvases painted between 1949 and 1956, and to some of his other late paintings of interiors. Such a resemblance would not be surprising, for Johns has close temperamental affinities to Braque. There's an extreme introversion that creates a formidable distance from others. And there's that artisanal approach to work: this is something not uncommon among French painters, and Matisse for instance certainly had it, though no one perhaps more intensely than Braque, who seems never to have forgotten his beginnings as a housepainter. Among American painters it is rare. Both those shared attributes are conducive to a shared tendency to nurse a work into existence through an interaction often prolonged for years between idea and realisation. Above all there is even a common atmosphere, present in Braque's Studios as it is in Johns's world as Carter Ratcliff so beautifully evokes it: 'Johns neither illuminates life and death nor tells us how he feels about these massive and murky topics. At most, he tinges them with his sensibility. The nature of that tinge is obscure, a matter one cannot even begin to address before withdrawing to an inwardness as private as Johns's own. His art induces us to be like him: entranced by the elusive but somehow always dependable hum of solitude.'

"The resemblance in the works was somewhat obscured at first by the strength of the presence in the Johnses of brushmarks powerfully reminiscent of Rauschenberg and de Kooning. It emerges clearly in paintings of 1984 such as Untitled in the Broad collection and is most obvious in works of the 1990s such as the two large canvases incorporating the ground plan of a house, especially Untitled l992-94. The common iconographic vocabulary of the relevant works includes a skull, a bowl, a jug, a massive arrow, lettering, balls, stars, a silhouette of a male figure, a picture or pictures within the picture, irregular biomorphic shapes filled by stripes or some other regular pattern. The style is a complicated version of Synthetic Cubism. The composition is divided into compartments, sometimes meshing or overlapping. Shapes often look like pieces of paper partly superimposed on others. There's a ubiquitous dialogue between long straight lines and long serpentine lines. The palette tends to be muted. The paint often varies in thickness and texture between one part of the canvas and another.

"It looks unlikely but is probably the case that the resemblance is something of which Johns is unconscious - that when calling certain pictures The Studio or In the Studio he wasn't thinking at all of Braque's series, that his constant use in the later works of trompe l'oeil nails is not an allusion to Braque's exploitation of that device in the heyday of Cubism, that any stylistic resemblance derives entirely from an inner affinity reinforced by the inspiration of Cézanne just as it may do when cross-hatch pictures such as The Dutch Wives and the Usuyuki series seem to be emulating the use of straight lines and a grisaille palette in Braque's late analytical cubist paintings to create a tangible space.