S. Benn & R. S. Peters 
Social Principles and the Democratic State (Routledge Library Editions: Political Science Volume 4) [PDF ebook] 

This book, originally published in 1959, makes explicit the social principles which underlie the procedures and political practice of the modern democratic state. The authors take the view that in the modern welfare state there are porblems connected with the nature of law, with concepts like rights, justice, equality, property, punishment, responsibility and liberty and which modern philosophical techniques can illuminate.