Pints and philosophical puzzles with Matthew Sweet. Each week Matthew goes to the pub to discuss a knotty conundrum with an audience and a panel of experts. Free will, exploitation, sex, sexism, blame and shame are just some of the topics to be mulled over in this series of The Philosopher's Arms. We look at the issue of 'free-riding', with Oxford philosopher Roger Crisp. Producer: Estelle Doyle.