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. Its classical usage refers to anti-authoritarian varieties of left-wing politics such as anarchism, especially social anarchism, whose adherents call it libertarianism, communalism, and libertarian Marxism, 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.