 Macpherson's best-known contribution to political philosophy is the theory of "possessive individualism", in which an individual is conceived as the sole proprietor of his or her skills and owes nothing to society for them.These skills (and those of others) are a commodity to be bought and sold on the open market, and in such a society is demonstrated a selfish and unending thirst for consumption which is considered the crucial core of human nature.Macpherson spent most of his career battling these premises, but perhaps the greatest single exposition of this view can be found in "The Political Theory of Possessive Individualism", where Macpherson examines the function of this particular kind of individualism in Hobbes, Harrington and Locke (and several writers in between, including the Levellers) and its resulting pervasiveness throughout most liberal literature of the period.