The slave is outside competition; the proletarian is in it and experiences all its vagaries. The slave counts as a thing, not as a member of society. Thus, the slave can have a better existence than the proletarian, while the proletarian belongs to a higher stage of social development and, himself, stands on a higher social level than the slave.
The slave frees himself when, of all the relations of private property, he abolishes only the relation of slavery and thereby becomes a proletarian; the proletarian can free himself only by abolishing private property in general.