Why is it so appalling to learn that the Duke and Duchess of Windsor employed a footman to hand-cut their lavatory paper? The entire history of art, architecture and design shows that there has been a great deal of disputing about taste. In fact, the only certain thing about taste is that it changes. But what is it? The Romans knew it without doubt; in the 18th century the virtuosi sat in their salons and pondered its meaning while a brittle Scarlatti keyboard piece entertained them. But in the 19th century, with the explosion of consumerism, all moral certainty disappeared and the notion of "good taste" was invented to normalize middle-class behaviour. In our own century taste has become a taboo since the judgements we make about dress, manners, food and art are painfully revealing of social and educational backgrounds which we would sometimes prefer remained obscure.