Within left-libertarianism, scholars such as Hillel Steiner, Peter Vallentyne, Philippe Van Parijs, Michael Otsuka and David Ellerman root an economic egalitarianism in the classical liberal concepts of self-ownership and land appropriation, combined with geoist or physiocratic views regarding the ownership of land and natural resources (e.g. those of John Locke and Henry George). Left-libertarians "maintain that the world's natural resources were initially unowned, or belonged equally to all, and it is illegitimate for anyone to claim exclusive private ownership of these resources to the detriment of others. Such private appropriation is legitimate only if everyone can appropriate an equal amount, or if those who appropriate more are taxed to compensate those who are thereby excluded from what was once common property". This position is articulated in contrast to the position of other libertarians who argue for a right to appropriate parts of the external world based on sufficient use, even if this homesteading yields unequal results. Some left-libertarians of the Steiner–Vallentyne type support some form of income redistribution on the grounds of a claim by each individual to be entitled to an equal share of natural resources.