Henri Cartier Bresson is the sorealist par excellence - even if he was probably unaware of it. On the other hand, he might have been unaware what a great photograph he was taking when he too this snap of Franco's Spain. How many photos did he take in those days and months to get just one like this. How can you plan for something so random and evocative? You can't. You have to just hang around for long enough to be at the right place at the right time. You have to respond to the passing moment, and then recognise what you have.

All these qualities are SOREALIST rather than SURREALIST. On the surface they look the same. This image is filled with foreboding and unconscious undetermined meanings, like many surrealist works. But there's a crucial difference. This is a picture of reality. Though we think about Cartier Bresson and his amazing eye, we are drawn beyond that - to the threat of violence, the persistence of poverty in the sun and shade of this Spanish alleyway. We think of the girl running by, and wonder what the boy is pondering. Is he scared for the future? Is he lost? And by extension, because he's a real boy in a real place, we wonder where he is now, if he's still alive, and whether he remembers this moment on that street, and what he feels now about what he felt then.

 Only a true record of events can stir this kind of nostalgia about time and the vanishing moment. Many potraitists and paintings make us wonder about their subjects - perhaps fear a vanquished soldier or a long dead beauty. They also make us look at the passing of time, and the persistence, even in paradise, of death: Et in Arcadia Ego. But the connection is never so powerful as in photography, where the photons that the emulsion of Cartier Bresson's film are unmediated through the trembling hand of a painter.

Compare Cartier-Bresson's work with De Chirico, a famous surrealist. They both have the same concerns: the play of shadow surface and illegible symbol. They both feed the unconscious with strange guesses and fears we cannot quite explain. But while De Chirico, as a surrealist, paints his interpretation of reality, and promotes the artist as visionary, Cartier-Bresson sees a boy in a baking Spanish alleyway, and the boy becomes the subject as much as him. There's a balance between object and subject, between inner life and outer mask, which is more like the work of Goya than the declared artiness of De Chirico.

Photography is the prime SOREAL ART, because it is more event than art from. More historical. More radical. It changed painting utterly in the 19th Century (see Manet) and relieved it temporarily of the burden of recording faces, representing reality. But this freedom of the visual arts came at a cost. Painting ceased to become the recording angel and, deprived of this necessary connection with immortality and mortality, 20th century art lost its bearings, and looked to conceptual art and sculpture to create a sense of uniqueness, to make an event that could match the sorealism of photography.