 At the same time, while pluralism is a key ingredient in Berlin’s argument for the importance of liberty, it also modifies and moderates his liberalism, and prevents Berlin from being (as many proponents of negative liberty in the twentieth century and after have been) a dogmatic, unqualified classical liberal or libertarian. Negative and positive liberty are both genuine values which must be balanced against each other; and political liberty of any sort is one value among many, with which it may conflict, and against which it needs to be weighed. Berlin was more sensitive than many classical liberal or libertarian thinkers to the fact that genuine liberty may conflict with genuine equality, or justice, or public order, or security, or efficiency, or happiness, and therefore must be balanced against, and sometimes sacrificed in favour of, other values. Berlin’s liberalism includes both a conservative or pragmatic appreciation of the importance of maintaining a balance between different values, and a social-democratic appreciation of the need to restrict liberty in some cases so as to promote equality and justice, and to protect the weak against victimisation by the strong (see 2002b, 214–15). Nevertheless Berlin remains a liberal in maintaining that the preservation of a certain minimum of individual liberty is a political priority. He justifies this view by an appeal to an empiricist version of a natural law argument, writing of the existence of ‘natural rights’ based on the way that human beings are constituted, mentally or physically; to attempt to alter or limit human life in certain ways is to block the desires, goals, aspirations inherent in being human as we know it (1996, 90–2). To deprive human beings of certain basic rights is to dehumanise them. While liberty should not be the only good pursued by society, and while it should not always trump other values, ethical pluralism lends it a special importance: for people must be free in order to allow for the recognition and pursuit of all genuine human values. Society should therefore make it a priority to provide the liberty necessary for Millian ‘experiments in living’ and for the perpetuation of social and personal variety (see Berlin 2002b, 218–51).