Norberto Bobbio was one of Italy's foremost thinkers. He taught at a number of universities, including Siena, Padua and Turin; his other works include Left and Right and Democracy and Dictatorship: The Nature and Limits of State Power.

Martin Ryle is Senior Lecturer in Continuing Education at the University of Sussex. His previous books include The Politics of Nuclear Disarmament, Ecology and Socialism, and Journeys in Ireland.

Kate Soper teaches philosophy and cultural theory at the University of North London. Her previous works include On Human Needs, What is Nature? Culture, Politics and the Non-Human and, with Verso, Troubled Pleasures.