Laurie Taylor considers why men 'cheat' in relationships. 78% of young male students have been unfaithful to their current partners according to the sociologist, Eric Anderson. He discusses men, monogamy and the reality of infidelity. They're joined by the sociologist, Lynn Jamieson. Also, the new politics of citizenship - Engin Isin, a Professor of politics at the Open University, explores the ways in which people embrace acts and causes which transcend national boundaries.Producer: Jayne Egerton.