Certainty and the dangers of conviction

From Galileo to Mandela, history is made by those with strong convictions. Yet as the philosopher Friedrich Nietzsche argued and Islamic State attest, those most convinced of their righteousness are often the most dangerous. Should politicians and the rest of us avoid convictions and see them as dangerous fantasies, or is conviction essential to leadership, action and public support? Philosophers Julian Baggini and Andrew Bowie and former Conservative politician Edwina Currie are convinced about conviction. Richard Coles hosts.