Unmarried heterosexual cohabitation is rapidly increasing in Britain and over a quarter of children are now born to unmarried cohabiting parents. This is not just an important change in the way people live in modern Britain; it is also a political and theoretical marker. Some commentators see cohabitation as evidence of selfish individualism and the breakdown of the family, while others see it as just a less institutionalized way in which people express commitment and build their families. Politically, 'stable' families are seen as crucial-but does stability simply mean marriage? At present...