Vermeer, Jan: Woman Holding a Balance (c1663)

For many years the artist Ian Breakwell, who died last autumn, kept a diary - a diary of things seen and things heard. There's an entry from March 1977, for example, where he's travelling on the London Underground, on the Northern Line, observing a man and a woman sitting opposite. Specifically, he observes this couple when the train stops in a station, and the advertising posters come into view.

"Leicester Square. Alongside his head is a grinning man. Between his head and her head a hand is slipping inside the top of a pair of trousers. Alongside her head is the mouth of a shark..

"Tottenham Court Road. Alongside his head two children are walking hand in hand down a country lane. He fiddles with his umbrella. Between his head and her head there is a flash of lightning. She pulls at her cuffs...

"Warren Street. Between his head and her head is a pair of buttocks in sheer nylon tights. He touches his lapels. Alongside her head is the face of the tiger. She strokes the little umbrella in her lap. He glances at her with a half smile which she returns."

How our daily lives are punctuated by such extravagant imagery! That's the general point. But there's also a vein of insidious comedy in these observations. The images seem as real as the people themselves. Images and people arrange themselves into spontaneous narratives. The people involved are quite unconscious of these compromising visual coincidences. But they seem also, through their small, nervous gestures, to be half aware of the strange contexts in which they keep arriving - the sharks and lightning and buttocks that lurk behind their heads.

People are always standing in front of things, but these line-ups don't usually last long enough to become really noticeable. It takes a particular situation, and a Tube train stopped in a station provides the necessary conditions: stationary viewer, subject and background. Another situation where these conditions are met is a picture.

In any picture, things lie fixedly in front of and behind one another. It's a basic, pretty well unavoidable pictorial device. It may be a matter of shape over shape, texture against texture. The near thing may appear to be interacting with the far thing -touching it, hitting it, being bisected or engulfed by it. There may be something more puzzling going on.

Vermeer's Woman Holding a Balance is an uncharacteristically shady scene. The daylight, which in other Vermeers floods in from the left, here just filters down from the top corner, catching the woman's pale skin, her white bonnet and fur trim, the strings of pearls on the table, the gilded ridges of the frame on the wall. The delicate metal balance, which she's holding up in her right hand, is hardly visible, apart from the thin highlights that gleam from the rims of its pans. The scales are empty. She is judging their level accuracy.

As often in Vermeer, things are on hold. We see a body holding itself still, in order to hold something else still - the right hand poised, the left laid steadyingly on the table. We see a mind absorbed, in an act of steady contemplation, as the woman watches the scales find their level. The lev-elness of this nearly invisible balance is both the focus and index of her stasis. Vermeer is a great mobiliser of the inherent stillness of a picture.

He's also very attentive to relations between in front of and behind. The woman stands in front of an oil painting on the back wall. Its frame contains her head and shoulders, as if it were the frame of her portrait. Visually, her head is inside the picture' the picture surrounds it. This juxtaposition could suggest that the picture is on her mind.

What's it of? Though it's quite dim, you can see (hopefully) that this is a Last Judgement. It shows the naked dead rising from their graves, and Christ at the top in a ring of light. The saved are on the left, the damned are being cast down on the right.

That's what is happening either side of the woman's head. The saved and the damned are being judged, separated and sent to their destinies. Just as the heads of Breakwell's couple are beleaguered by advertising imagery, this woman's head lies in the middle of the end of the world.

The juxtaposition is especially pointed because of what she's doing. A woman holding a balance is set against the Last Judgement, the weighing of souls: there must be a connection. And yet the woman herself shows no inkling of it. She seems alone, unaware of being viewed at all. Her head - though for us it's set in the midst of the crack of doom, directly beneath Christ the Judge - is held at a gentle tilt, in the most serene expression. Her calm, silent, solitary act of appraisal is as far as can be from the Day of Wrath.

The point of the juxtaposition seems, in fact, to be negative. The terrific scene that rages around her, an action scene in a baroque manner, doesn't in fact enter her head, or jolt her stillness, at all. It only ups her serenity.