The basis of Smith’s theories about the division of labor in human production rests in his repeated reference to “the natural” effects of production. Marx, on the other hand, understands production as a structure that is premised on social inequalities amongst humans. Where Smith regards “self-interest” as the natural force behind increasing a nation’s wealth, Marx regards differences in social class as the source of exploitation in labor. Smith idealizes the division of labor, and Marx & Engels both regard exploitation of social inequality as the basis for divisions in labor.