Cohen argues that the concept of self-ownership is favourable to Rawls's difference principle as it ensures "each person's rights over his being and powers" - i.e. that one is treated as an end always and never as a means - but also highlights that its centrality provides for an area of common ground between the Marxist account of justice and the right-wing libertarianism of Robert Nozick. However, much as Cohen criticises Rawls for treating people's personal powers as just another external resource for which no individual can claim desert, so does he charge Nozick with moving beyond the concept of self-ownership to his own right-wing "thesis" of self-ownership. In Cohen's view, Nozick's mistake is to endow people's claims to legitimately acquire external resources with the same moral quality that belongs to people's ownership of themselves.