Tim Noble and Sue Webster, Gagosian Gallery, London

The past fortnight having possibly left you with short-term memory loss, I'm going to do a small show this week so small, in fact, that it consists of only one work, although the work in question is admittedly large. Called Sacrificial Heart, it is a sculpture by that sulphurous couple Sue Webster and Tim Noble. You can see it in the window of the Gagosian Gallery's new space in Mayfair in west London.

Of course, there are other things to look at in Davies Street, that being rather its point. Gordon Ramsay's restaurant is up the road from Gagosian and Vivienne Westwood is right opposite. Sacrificial Heart is, as its name suggests, a heart, measuring perhaps a metre and a half high and wide and made out of moulded fibreglass. It is, as you would also expect, red and shiny, its redness and shininess being highlighted by dozens of multicoloured fairy lights that wink on and off as the work turns on its stand. Through the heart is a fibreglass dagger, its tip dripping with drops of fibreglass blood that swing as the sculpture goes round. Given Westwood's trademark royal orb logo in the window opposite, it seems possible that Sacrificial Heart is advertising some brand of luxury good; and so, in a sense, it is.

That "good" is art. T J Clark's excellent book, The Painting of Modern Life, floats the idea that Baudelaire's flneur may have been the world's first window shopper. The invention of plate glass allowed for department store vitrines (and, come to that, for big windows in private galleries), and that in turn led to what a certain kind of art theorist calls "the commodified gaze". This was fixed as much on art as on fashion, so that Noble and Webster's link with Vivienne Westwood is not as impossible as it sounds.

The question that then arises a question I imagine the artistic duo want us to ask is whether Sacrificial Heart is just another commodity, if works of art are really no different from rhinestone bustiers. This doubt has plagued the YBA generation mightily of late. (Witness the rise of Bling Art, as epitomised by Damien Hirst's 50m diamond-and-platinum skull For the Love of God.) What, apart from five metres of tarmac, separates Noble and Webster's work from Westwood's? How is her punk chic different from theirs?

It's a question that cuts to the quick of Western culture, and not just in terms of its aesthetics. On one level, Sacrificial Heart raises the same kinds of doubts about fashion and kitsch as those raised by Jeff Koons's balloon bunnies and gilded Michael Jacksons. But Noble and Webster's work also draws on other iconographies, among them those of Christianity and biker gangs.

The Sacred Heart of Jesus is a central symbol of Catholic worship, a metaphor for Christ's sufferings and love. Sacr Coeur, the great hilltop church of Paris, is built to its devotion. Like Sacrificial Heart, the Sacred Heart is bound with thorns and run through by a dagger: but then that same image can also be found tattooed on the arms of Hell's Angels. If you're trying to locate Noble and Webster's new work culturally, in other words, you could bypass Westwood for the Church of the Immaculate Conception in Farm Street, or you could equally head for the Salvation Army hostel on Hanover Square.

All of which is to say that Sacrificial Heart comes spiked with cultural collisions of art and fashion, good and bad, high and low, the sacred and profane. Other people's work has mined this same lode the Chapman brothers' various hells, the porn-star Saint Sebastians of Pierre and Gilles but what makes Webster and Noble's so strong is that it doesn't allow for tidiness. The pair are genuinely nasty artists, and I mean that as a term of praise. What is the difference between a biker's tattoo and divine love? Between art and fashion, good and bad or anything and anything else?

Sacrificial Heart turns quietly on its stand and says nothing. It is repellent and, in a Vegas kind of way, really quite pretty. It is also horribly consistent. Ten years ago, Noble and Webster made a two-dimensional wall piece of the same subject and called it Toxic Schizophrenia. Times have changed but their work has not, other than to become a little fuller, a bit nastier. I'm not recommending this show as a spiritual pick-me-up for the New Year, but if you'd like your assumptions shaken for 2008, then Davies Street is a good place to start.

Gagosian, Davies Street, London W1 (020-7493 3020) to 23 February

Further reading 'The Painting of Modern Life', T J Clark (Princeton University Press)