These inefficiencies manifest themselves as social contradictions in society which are, in turn, fought out at the level of class struggle. Under the capitalist mode of production, this struggle materializes between the minority who own the means of production (the bourgeoisie) and the vast majority of the population who produce goods and services (the proletariat). Starting with the conjectural premise that social change occurs as result of the struggle between different classes within society who contradict one another, a Marxist would conclude that capitalism exploits and oppresses the proletariat, therefore capitalism will inevitably lead to a proletarian revolution. In a socialist society, private property—as the means of production—would be replaced by co-operative ownership. A socialist economy would not base production on the creation of private profits, but on the criteria of satisfying human needs—that is, production for use. As Friedrich Engels explains: