), "Great Political Thinkers: Machiavelli, Hobbes, Mill and Marx", Oxford University Press, Oxford, 1992* "The Expanding Circle: Ethics and Sociobiology", Farrar, Straus and Giroux, New York, 1981; Oxford University Press, Oxford, 1981; New American Library, New York, 1982.
), "Great Political Thinkers: Machiavelli, Hobbes, Mill and Marx", Oxford University Press, Oxford, 1992* "Animal Factories" (co-author with James Mason), Crown, New York, 1980* "The Expanding Circle: Ethics and Sociobiology", Farrar, Straus and Giroux, New York, 1981; Oxford University Press, Oxford, 1981; New American Library, New York, 1982.