Martin Scorsese recently explained how the Taxi Driver sequence in which Robert de Niro arms himself for slaughter was an allusion to a childhood memory of a Hollywood western, one in which guns gleamed with a magical potency. And this didn't seem like a pathological or distasteful fascination on Scorsese's part - more a literate recognition of cinema's long infatuation with the weapon.
But there is a curiosity here to be explained. What is it about cinema that makes it so peculiarly lovelorn about guns? It can't simply be visual appeal - because if guns are a compelling subject in this century (and they surely are), we still have to explain why they are almost entirely absent from contemporary art.
There are exceptions to the rule. Pop Art had a brief flirtation with the gun, attracted by its mechanical sheen and explosive impact, but Pop Art is often emulating cinema (by way of the comic strip, itself a cinematic form) so that may not really count. Similarly the sculptor Michael Sandle created a massive bronze Mickey Mouse manning a vast machine gun, a perfectly machined replica of a real weapon - but that, too, was partially interested in shocking the viewer with inappropriate matter.
What's more, though there have been great paintings with guns in them - Goya's Third of May 1808 and Manet's The Execution of the Emperor Maximilian - both works are revealing about the difficulties guns present for the painter.
In Goya's masterpiece, an almost journalistic record of French reprisals in Madrid, the barrels of the soldiers carrying out the massacre are at the very heart of the composition - every eye in the picture bends towards their implacable geometry. The irregular curve of the soldiers' backs, legs tensed wide and heads lowered to aim, sweeps upwards into a piercing horizontal which shoots the eye across to the victims. Goya has chosen the moment just before the trigger tightens and human will is irretrievably converted into mechanical action but in truth he didn't have a lot of choice about it.
In his picture Manet chooses the moment just after - fire is visible at the muzzles and the victim is still upright - but his options are limited, too: an either/or that grips the event itself like a vice.
Guns squeeze complex moral action down to a single percussion so that it is virtually impossible not to perceive these images as a kind of snapshot (Kenneth Clarke said of the Goya: "It looks like a flashlight photograph and has none of the build-up of other big pictures of historical events"). And while photography, a medium of frozen instants, is, if anything, strengthened by such subject matter, painting finds in it only a bleak constriction - immensely powerful in Manet and Goya but essentially unrepeatable. In artistic forms that have time on their hands the matter is quite different: a gunshot cannot punctuate a painting because a painting doesn't have a temporal sequence that requires it. In a play, though, the gun offers the possibility of the most dramatic full stop or semi-colon - and the moment it appears, a sort of promise is made to the audience.
Indeed the potential for transformation a gun offers is so facile and tempting that the offstage shot rapidly became a dramatic cliche. Samuel Beckett makes a dark joke about this in Happy Days, in which an unexplained revolver lies on set, eventually proving itself as incapable of action as his characters. As a narrative medium, cinema naturally shares this appetite for ready tension. This can easily sound sexual - the arousal of the sight of the gun finally discharged with its firing - but the venerable association between gun barrels and the phallus is, I think, an error (even if it is an error with some truth in it).
If the gun stands for any part of our bodies it is the finger - pointing in aggression, identifying a target (why else do we talk of snipers "picking off" their victims). In cinema the accusing finger is almost as potent a weapon as the gun; think of all those scenes in which the anger of a mob is suddenly condensed and directed along an extended digit. It isn't just rude to point, it is sometimes deadly. The pointing finger is one of our most primal gestures of threat and the fact the human hand has shaped the gun into an echo of itself - grip bunched like fingers, hammer cocked back like a thumb - is at the heart of the weapon's awful glamour, its supernatural extension of our bodily powers. And cinema is (as well as being a mechanical, photographic and narrative art) an art of pointing, fascinated by its ability to tell us exactly where and how to look.
Both things come together in one of the purest expressions of gun culture ever produced - a short television film by Alfred Hitchcock in which a small boy playing at cowboys picks up his father's loaded pistol. The almost unbearable sequence that follows, in which every person who enters the frame is seen by the boy as an imaginary enemy and by us as an imminent victim, explains everything you need to know about cinema's infatuation with the gun.