In 1971, a previously obscure Harvard philosophy professor, John Rawls, published a book that ultimately brought him acclaim as “America’s greatest political philosopher.” In the book, “A Theory of Justice,” Rawls set forth an account of justice in the form of two principles, ordaining respectively that people’s “equal basic liberties” — such rights as freedom of speech, freedom of conscience, and the right to vote — should be maximized, and that inequalities in social and economic goods other than liberty are acceptable only if they promote the welfare of the “least advantaged” members of society. (He termed the latter the “difference principle.”)

Three years after the appearance of “Theory,” a departmental colleague of Rawls, Robert Nozick, published a libertarian response, “Anarchy, State, and Utopia,” which argued that nothing more than a “minimal state” devoted to protecting people against crimes like assault, robbery, and fraud could be morally justified.