People have often referred to conflicts between the concepts we use to understand the best way to live - ideas like Liberty, Equality, Justice, Democracy. You need to suppress one to achieve the other, and this - the argument goes - proves that they are not universal moral concepts. In his engagingly titled new book, Justice for Hedgehogs, the US philosopher Ronald Dworkin seeks to show that there is no incompatibility between these ideas because they are part of a single unified value, they only appear to conflict because of the way we are looking at them. But how do we ascribe this value with a universal role without recourse to God, or some other metaphysical entity? Laurie discusses the idea with Ronald Dworkin and AC Grayling.