Left-libertarianism, also known as egalitarian libertarianism, left-wing libertarianism or social libertarianism, is a political philosophy and type of libertarianism that stresses both individual freedom and social equality. Left-libertarianism represents several related yet distinct approaches to political and social theory. In its classical usage, it refers to anti-authoritarian varieties of left-wing politics such as anarchism, especially social anarchism, whose adherents simply call it libertarianism, communalism, and libertarian marxism, which are collectively termed libertarian socialism. A portion of the left-wing of the green movement, including adherents of Murray Bookchin's social ecology, are also generally considered left-libertarian.