Historian Eric Foner argued that a free-labor ideology dominated thinking in the North, which emphasized economic opportunity. By contrast, Southerners described free labor as "greasy mechanics, filthy operators, small-fisted farmers, and moonstruck theorists". They strongly opposed the homestead laws that were proposed to give free farms in the west, fearing the small farmers would oppose plantation slavery. Indeed, opposition to homestead laws was far more common in secessionist rhetoric than opposition to tariffs. Southerners such as Calhoun argued that slavery was "a positive good", and that slaves were more civilized and morally and intellectually improved because of slavery.Karl Marx, developing his economic theories in the mid-19th century, expressed a class-based view of conditions in North America in 1861, believing "that the defeat of the 'slave-holding aristocracy' would enable the world's free workers to prosper as small landholders on America's endless frontier".