Negative liberty is the absence of obstacles, barriers or constraints. One has negative liberty to the extent that actions are available to one in this negative sense. Positive liberty is the possibility of acting — or the fact of acting — in such a way as to take control of one’s life and realize one’s fundamental purposes. While negative liberty is usually attributed to individual agents, positive liberty is sometimes attributed to collectivities, or to individuals considered primarily as members of given collectivities.
The idea of distinguishing between a negative and a positive sense of the term ‘liberty’ goes back at least to Kant, and was examined and defended in depth by Isaiah Berlin in the 1950s and ’60s. Discussions about positive and negative liberty normally take place within the context of political and social philosophy. They are distinct from, though sometimes related to, philosophical discussions about free will. Work on the nature of positive liberty often overlaps, however, with work on the nature of autonomy.
As Berlin showed, negative and positive liberty are not merely two distinct kinds of liberty; they can be seen as rival, incompatible interpretations of a single political ideal. Since few people claim to be against liberty, the way this term is interpreted and defined can have important political implications. Political liberalism tends to presuppose a negative definition of liberty: liberals generally claim that if one favors individual liberty one should place strong limitations on the activities of the state. Critics of liberalism often contest this implication by contesting the negative definition of liberty: they argue that the pursuit of liberty understood as self-realization or as self-determination (whether of the individual or of the collectivity) can require state intervention of a kind not normally allowed by liberals.