The big issue...

A vast steel hoop stands partially blocking the main entrance to Tate Modern while at the other end of the building, a little more than 500 feet away, stands another. Halfway between them in the hangar-like space that is the museum's main hallway another hoop is turned downwards to hover over the platform that interrupts the space. Between the three is stretched, like the taut fabric of an airship, a high swooping shape in dark-red PVC, its sheen reflecting the museum's lamps and skylights. This technically accomplished sculpture, its shape reminiscent in places of a bone, in places of a massive ear trumpet, is Anish Kapoor's answer to the conundrum posed to artists by Tate Modern's gigantic Turbine Hall.

This vast entrance hall, 115 feet high, may cause first-time viewers to draw in their breath, but it seems to belittle most art placed in its long, deep and often gloomy space. Kapoor conquers it in the most outright way possible, by occupying its full height, width and breadth.

The sculpture is named after Marsyas, who, according to Greek legend, challenged Apollo and was punished for his presumption by being flayed alive. In some versions of the tale, his blood formed a river that came to bear his name; Kapoor says the flowing, translucent blood-red fabric of Marsyas is supposed to be read as skin (and not, it seems, white skin) stretched tight to form a "sky" above the viewer.

Kapoor, since first coming to attention in the Eighties with small, brightly coloured constructions dusted with powdered pigment, has gone on to pursue a successful international career.

He represented Britain at the Venice Biennale in 1990, won the Turner Prize in 1991, and had a major show at the Hayward Gallery in 1998. His sculptures and installations, with bulging and hollowed-out forms, have often been praised for their apparent emptiness that allows the viewer sublime glimpses into the void through a wide variety of apertures.

Kapoor has made forthright statements about his art, claiming that it opposes the phallic constructions of modernist sculpture (for instance, the work of Brancusi) in favour of its opposite.

Indeed, much of his sculpture and drawings dwells insistently on such orifices, and while such a predilection in a "Young British Artist" might incline towards toilet humour, Kapoor, being of an older generation and of Indian origin, is granted the dispensation that his orifices open onto not merely flesh but metaphysical dilemmas and eternal mysteries.

Yet, with a work of such gigantic size, can we be content with these musings, or should we ask, as we would of any commissioned piece, "What is it for?" A triad of names is elevated by it: first, naturally, that of Kapoor himself. It is an open question whether artists can make works that do not aggrandise themselves, but Marsyas is a visual register of a considerable inflation of the ego that declaims: "I will dominate the space!" The second beneficiary is Tate Modern, which in celebrating its contents celebrates itself.

Expecting an institution such as this to take a critical view of the contemporary work it displays - let alone commissions - is like asking an advertising firm to reveal the flaws of its clients.

This brings us to the final beneficiary: Unilever. The food-and-household-products-giant has entered into a partnership with Tate, by which it gives £1.25 million over five years to sponsor the Turbine Hall displays. Marsyas is a particularly gruesome subject, and Kapoor's work, in which the sky is turned to bloody flesh, could be read as a grim comment on the totality of human suffering, and even on its uneven distribution according to skin tone.