This expanded edition, which begins by reproducing the 1970 edition in its entirety, goes on to present eleven new chapters of new arguments and results. As in the original version, the new chapters alternate between non-mathematical chapters completely accessible to all, and those which present mathematical arguments and proofs. The reader who prefers to shun mathematics can follow all the non-mathematical chapters on their own, to receive a full, informal understanding. There is also a substantial new introduction which gives a superb overview of the whole subject of social choice.