The Idea of Justice, published in 2009, is a major philosophical work by Amartya Sen. It offers a critique of the theory of social justice that has long left practical realities far behind. As opposed to the transcendental theory of justice identifying perfectly just social arrangements, Sen favours focusing on the comparative judgments of what is “more” or “less” just, and on the comparative merits of different societies that actually emerge from certain institutions and social interactions. At the heart of Sen’s argument is a respect for reasoned differences in our understanding of what a “just society” really is. Therefore, a comparative perspective on justice can guide us in the choice between alternatives that we inevitably face.This symposium brings together eleven internationally acclaimed scholars who have debated and put forth their views on Sen’s idea of justice, further contributing new ideas to the nature of social justice.