In his left hand, the boy holds a playing card, an ace of hearts. He studies it, his lips pursed as though the red symbol on the card is their imprint. The boy is not interested in kissing, though – the neglected gaming-chips on the table spell out the innocence of his youth. Nor is his interest in the card's value as an ace. Like other boys on the wall in this room, he is using it to build a house: more properly, a château de cartes, the four young card-players being French, the work of Jean-Baptiste-Siméon Chardin.
Think of ancien régime painting and your mind, probably and properly, will fill with images of Chardin's contemporary, François Boucher: Rococo nudes doing nameless things in bushes, the voluptuous spirit of Versailles. Chardin, by contrast, painted copper pans, still lifes of fish, maids washing up, boys playing tops or cards. That makes him mysterious.
The 18th-century French art market was dominated by aristocratic patrons. This picture, The House of Cards, was owned by – perhaps painted for – Victor Amadeus, Prince of Carignano. The house-building boy is clearly a servant, snatching an illicit moment of leisure at his master's gaming table. Why would a Savoy princeling want to own such an image, at best plain and demotic, at worst seditious?
What makes this question compelling is the place where we see The House of Cards, a damask-lined salon in Waddesdon Manor. Waddesdon, built in the 1880s, is the supreme example of le goût Rothschild, the Rothschild taste. Yet Rothschilds have been collecting Chardins for 200 years. Charlotte de Rothschild, in Paris in the mid-19th century, owned 20 of them, most destroyed when the house in Bath where the paintings had been sent for safekeeping was bombed in the war. Her descendant, the current Lord Rothschild, heads the trust that owns The House of Cards. The question of why upstairs people like these downstairs images still hangs in the air.
An obvious answer might be play-acting of a Marie-Antoinette-in-the-milk-shed kind, although a look at the works in this show quickly rules that out. They are too real. Equally, they are not subversive. Because the scumbled austerity of Jacques-Louis David, that great lyricist of the Revolution, carries echoes of Chardin, it is easy to think of Chardin as sharing David's politics. Since he died a decade before the Revolution, that plainly cannot be. These four boys are not rebellious servants, little Figaros in the making. The point of their servitude is that, like all good servants, they do their job invisibly.
Which is to say that they do not get in the way, that we do not worry about them, even as cyphers of a hidden meaning. The house of cards may be a symbol of the fragility of life, but then one of the boys – bought by Catherine the Great, now on loan from Washington – isn't building a card-house. He is playing capucins, a game in which cards are folded to look like Capuchin friars, stood in a row and knocked over like dominoes. He is in control of the game, of his fate as a player. The four suits of cards may suggest love and death, poverty and nobility, but that is not the point of the four paintings in which they appear. Rather, they are studies in absorption, of the moment when concentration makes the world stand still.
Look again at these four boys, side-by-side on the wall. Despite their similarities, they are different. One, the National Gallery's House of Cards, has a sitter whose identity we know, the son, like Chardin himself, of a cabinet-maker. The light in this picture is clearer than in the other three. The left-most boy, from the Louvre, is the most dishevelled, and the only one not in full profile. Two face left and two right; the Waddesdon picture has Rubens-like drapery, so that we peer at its subject as past a curtain. The value of seeing these works together – a rare occurrence – isn't in spotting their differences, though, but in noting what stays the same.
Chardin liked to paint works in series, and these four boys were done in the space of two years, 1735 to 1737. Their meticulousness, their utter absorption, reflects his own absorption in his task: the boys are himself, forever on the point of success or failure. That is what makes this quartet so absorbing to us, whether prince or plutocrat or mere art critic. You may never get the chance to see the four Houses of Cards again, so get to this small, perfect show if you can.
To 15 Jul (01296 653203)
Trace the influence of Picasso on a wide range of British artists from Wyndham Lewis to Hockney via Bacon, or just glory in the Picassos on show at London's Tate Britain (to 15 Jul). That legacy is traceable too in the work of Keith Vaughan, whose shift from romanticism to abstraction is the focus at Pallant House, Chichester (to 10 Jun).