Almost every country today contains adherents of different religions and different secular conceptions of the good life. Is there any alternative to a power struggle among them, leading most probably to either civil war or repression? The argument of this book is that justice as impartiality offers a solution. According to the theory of justice as impartiality, principles of justice are those principles that provide a reasonable basis for the unforced assent of those subject to them. The object of this book is to set the theory out, explain its rationale, and respond to a variety of criticism that have been made of it. As the second volume of his work-in-progress, A Treatise on Social Justice, this work lies at the heart of a thriving academic debate which the author has played a key role in shaping.