This evening, those with more than £15m to spare could splash out on one of the world's greatest impressionist paintings. Claude Monet's Nympheas, painted in 1904, is among the earliest in the artist's waterlily series to focus almost entirely on the surface of the water.

It is now regarded as a very influential work in the movement towards abstraction in the twentieth century - and is also, of course, luminously beautiful. The sale at Sotheby's in London is generating enormous excitement, not least because the painting, one of the few Monets remaining in private collections, has not been seen in public since 1936.

In this case - as with the other big names in the sale, including Matisse, Renoir, Modigliani, Toulouse-Lautrec and Picasso - bidders are putting their money on entirely bankable commodities, but would they have been as keen on Nympheas in 1904?

The question arises in the wake of one of the contemporary art world's cautionary tales. Damien Hirst, who hit the headlines as the new enfant terrible of British art in 1990, with A Thousand Years, a glass case containing maggots feeding on a dead cow's head, went on to make hundreds of "spin paintings", created by dribbling paint over a spinning canvas. The buyers who got out their chequebooks, emboldened by the knowledge that the collector Charles Saatchi was buying Hirst's work, included the theatre director Sir Trevor Nunn, who reportedly paid £27,000 for one of the swirly paintings.

However, in his new autobiography, the actor Keith Allen claims the painting was in fact created by Hirst's two-year-old son along with Allen's son, then 10. Sir Trevor has since said he sold the painting for a profit of some £20,000.

The new owners may not see the joke. An art market with newly monied Chinese and Russian oligarchs out-bidding one another for trophy paintings is tempting old families that have been guarding their grand collections to sell choice pieces. The really smart thing to do, however, is to spot new talent and buy what may turn out to be iconic 21st-century works. The impoverished art-lover's alternative to Sotheby's and Christie's summer sales is the degree show.

A tour of Glasgow School of Art's show yesterday revealed the usual mix of the beautiful and the bizarre, the technically accomplished and the iconoclastic. Identifying the original mind amid the youthful take on the world's ills is challenging. Is that still true of Monet?