Traditionally, left-libertarian schools are communist and market abolitionist, advocating the eventual replacement of money with labor vouchers or decentralized planning. Contemporary left-libertarians such as Hillel Steiner, Peter Vallentyne, Philippe Van Parijs, Michael Otsuka and David Ellerman believe the appropriation of land must leave "enough and as good" for others or be taxed by society to compensate for the exclusionary effects of private property. Socialist libertarians such as anarchists (green anarchists, individualist anarchists and social anarchists) and libertarian Marxists (council communists, De Leonists and Luxemburgists) promote usufruct and socialist economic theories, including collectivism, mutualism and syndicalism. They criticize the state for being the defender of private property and believe capitalism entails wage slavery.