Rana Mitter talks to Harvard moral philosopher Michael Sandel about justice, examining how we arrive at our notions of right and wrong. Should we not always tell the truth? Is killing sometimes morally justified? Considering the role of justice in society and in our lives, Sandel argues in his new book Justice: What's the Right Thing to Do? that an understanding of philosophy can help us make sense of politics, religion and morality. Michael Sandel gave this year's BBC Radio 4 Reith lectures and his class at Harvard University is famous for attracting huge numbers of students - more than 1,200 each session. His influence is such that Matt Groening and his fellow creators of The Simpsons poked fun at Sandel by partly modelling the morally suspect Montgomery Burns character on him.