When the definitive history of political theory in the twentieth century is written, Isaiah Berlin will take his place as one of the most distinguished representatives of the liberal tradition. In "Two Concepts of Liberty", he distinguished between negative and positive liberty, noncoercion and self-mastery, identifying the former with liberalism and the latter with political doctrines that evolved in antiliberal directions. Berlin's determination to understand cultures and their characteristic thinkers on their own terms has given rise to the suspicion that he was a relativist. He distinguished between pluralism, which he espoused, and relativism, which he repudiated. Similarly, although liberty and decency require an economic minimum, they do not dictate socialism or even social democracy. Turning from method to substance, Berlin's clarification of the differing dimensions of liberty and their practical consequences has often been criticized but never dismissed.