It sounds too obvious to say, so I'll say it: a private collection is different from a public collection.
The Barnes Foundation in Philadelphia may have more Renoirs than the Musée d'Orsay, but, unlike the d'Orsay's, they were paid for by one man with views on art that were, shall we say, idiosyncratic. As a result, the Barnes is both an agglomeration of artworks and itself a work of art, which makes its imminent destruction by Philadelphia's city fathers a mortal sin. To a greater or lesser extent, this same dual nature holds true of all private collections – the Frick, say, or the Maeght, the Costakis or, much less well known, the Della Ragione Collection.
Alberto della Ragione was born in Campania in 1892, moved to Genoa as a child, and trained as a naval engineer. He began to buy pictures in his thirties, admitting in a later memoir that at the time he believed real art to have ended in 1900. To some extent, this feeling seems never quite to have left him.
Although della Ragione lived through important moments in Italian abstraction and on into the era of Arte Povera (he died in 1973), his tastes remained mostly classical and figurative. Part of his collection, donated in 1970 to the Musei Civici in Florence, is now on show at the Estorick in London under the title From Morandi to Guttuso – slightly misleading, since it suggests an even distribution of works between 1907 and 1987, the year Giorgio Morandi started painting and the year Renato Guttuso stopped. In fact, by far the greater number of the 260 objects bequeathed by della Ragione to the city of Florence date from a single decade, 1935 to 1945. All are Italian.
So, a tightly focused collection in terms of time, style and geography: what you will find at the Estorick is not an encyclopaedia of 20th-century Italian art but a short story. Or rather, part of a story, since context is largely missing from it. While the catalogue talks us through movements in Italian art history, from the Metaphysical Painting of the young Morandi to Guttuso's membership of the Milanese group known as Corrente, it is light on politics. In 1935, the probable year of Giorgio de Chirico's painting Les bains mystérieux, Mussolini's troops invaded Abyssinia. Even as Guttuso was painting Scantily Clad Women in 1940, Italy entered the Second World War on the side of Nazi Germany. Neither of these things is mentioned in the exhibition's signage.
I don't mean to sound like Basil Fawlty, but shouldn't they be? Morandi was a wonderful painter, and his two Still Lifes in this show, made a decade apart, are beautiful and beautifully juxtaposed. But Morandi was also a man of his time. The earlier work was painted while he was associated with the Strapaese, a pro-fascist regionalist group. By the time of the second painting, his political tastes had changed: in 1943, Morandi would be arrested as an anti-fascist fellow traveller. The later Still Life is much looser than the earlier, its palette more sober, less contrasted. Without leaping to any easy conclusions, wouldn't history provide an interesting way of looking at this?
As to Guttuso, he certainly had nothing to hide. A Sicilian, he was a communist, an anti-fascist partisan and, in later life, an anti-mafia representative in the Italian parliament. As a young man in the late 1930s, he was also a member of Corrente, a group-cum-periodical with a distin-guished history of subverting fascism without being seen to do so. Corrente's final incarnation was as a gallery, this being run by Alberto della Ragione until it finally closed in 1944. That it lasted that long was due to the group's policy of keeping its visual cards close to its chest. There is nothing in any of the Corrente works in this show – none in any of the works at all – to suggest what was going on in Italy as they were made or to hint at political allegiance.
And that, perhaps, is the most compelling thing about From Morandi to Guttuso. What really catches the eye is what isn't there. In place of (say) the crashed fighters of a Paul Nash or the apocalyptic storm clouds of a John Piper, there is only a melancholic emptiness. You see it in the blank-eyed houses of Mario Mafai and Mario Sironi, the non-committal strangeness of Carlo Carrà's beach huts or the spatial impossibility of de Chirico's cabanas. "What is going on here?" you find yourself asking, again and again. And the answer always comes back: Nothing at all.
To 3 April (020-7704 9522)
Charles Darwent chips away at the Royal Academy's Modern British Sculpture show
Tate St Ives has a retrospective of Peter Lanyon's abstract paintings, right, and sculptures to 23 Jan, while London's White Cube is showing The Urethra Postcard Art of Gilbert & George, 155 collages made between 1972 and 1989 which (unlike the duo's large-scale photographic work) show a gentle humour. To 19 Feb.