AS you fight your way through the Christmas crowds, ponder this theory from the University of York - "I shop therefore I am."

A leading sociologist has concluded that, far from being an orgy of materialism, frenetic shopping activity is part of an important basic quest to convince yourself that you really do exist.

Professor Colin Campbell argues that shopping is one of the most important ways in which people can discover their own individuality.

And consumers are not defined by what they buy, but through exposing themselves to a wide range of products and services.

"Viewed in this way, the activity of consuming can be considered as a vital and necessary path to self-discovery, while the marketplace itself becomes indispensable to the process of discovering who we are," says Mr Campbell.

In his paper, I Shop Therefore I Am, Mr Campbell, who specialises in studies of shopping and consumerism in general, says modern shoppers are defined by the prevalence of wants over needs.

He says previous generations were far more likely to see themselves in terms of their family, religion, race and nationality, while modern people are in some ways defined by shopping tastes and trends.

He adds: "They would have seen themselves as farmers or fishermen, fathers, Presbyterian or Catholic, Englishman or Swede, rather than through their taste in wine, music or leisure-time activities."

Mr Campbell says religion has also been affected by the same social trends, with individuals instead opting for a "spiritual supermarket" of their own selection of beliefs.

On fashion, he says people need regular exposure to fresh stimuli if boredom is to be avoided, with "retail therapy" replacing some forms of human group interaction.

He says: "It is justifiable to claim not simply that we live in a consumer society, or are socialised into a consumer culture, but that ours is in a very fundamental sense, a consumer civilisation."

Updated: 11:12 Monday, December 23, 2002