Marx never doubted that capitalism was a social system, but he also argued that the material imperatives of capitalist societies were what really shaped their cultures and social institutions. Governments, laws, customs, and beliefs were all superstructures that the bourgeoisie built atop the foundation of a capitalist economy. Twenty years after Marx's death, however, another German social scientist, Max Weber, reversed this equation. Defining capitalists as seekers after "forever renewed profit by means of continuous, rational, capitalistic enterprise" (p. 18), and agreeing with Marx that capitalism could not exist without free labor (because one could not fully monetize and rationalize unfree labor), Weber diverged from his predecessor in asking whence these driven capitalists and their willing workers came, and in finding the answer not in their material circumstances but their cultural values. Capitalism, Weber argued, wasn't the product of commerce, mechanization, or corporate organization. It originated instead in a "social ethic" (54), the belief that one's earthly labor constituted a spiritual calling and that one had a religious duty to perform it well.
The capitalist, in Weber's view (expressed in his Protestant Ethic and the Spirit of Capitalism [Prentice-Hall, 1904/1977), revolutionized the world economy not with his techniques but with this ethos, which drove him to hard labor, "rigor[ous]...supervision" of his employees, and unrelenting maximization of output and profits (67-68). Weber tracked this ethic to the "Calvinistic diaspora" (43), particularly early modern Holland, England, and New England, the latter of which produced one of the world's first bourgeois ethicists, Benjamin Franklin, before it produced a capitalist economy. Calvinists, Weber observed, believed that mankind was depraved and helpless in God's eyes, and this belief endowed them with "a feeling of unprecedented inner loneliness" (104), unknown to Catholics and Lutherans. Unable to assuage this loneliness and anxiety through prayer or good works - neither of which Calvinists believed could help them achieve divine grace - Calvinists threw themselves instead into "intense worldly activity" (112). By the seventeenth century, Calvinist/Puritan theologians like Richard Baxter were arguing that constant labor was the Christian's primary duty, and that wasting time and losing opportunities to make profits were actually sinful, the former because it made one lose opportunities to advance God's work, the latter because it wasted the resources God wished to put into one's stewardship (157-58, 162-63).
The Calvinist's quest for self-perfection through work and material acquisition swiftly turned into a quest for continual and systematic increases in economic output, and the economies of nations with a large Calvinist population soon turned into productivity engines, emphasizing continual growth in profits and output at the expense of wages, consumption, or any of the ordinary pleasures of living. Indeed, since the Calvinist/Puritan's greatest earthly duty was to his work and "his possessions, to which he subordinate[d] himself as an obedient steward" (170), his work and wealth became more important, and one might say more holy, than any of the people who produced that wealth. The Protestant capitalist wasn't afraid of amassing possessions and growing rich; so long as he re-invested rather than consumed his wealth it would not block his entry into heaven. Nor was he opposed to inequalities of wealth, since these were ordained by God. Nor did he feel any obligation to pay his employees a decent wage, since if they were fellow Calvinists they would feel their work was its own reward, and if they weren't then they were sinners who would only work if goaded to it by the threat of starvation.
To me, and I suspect to some of Weber's other readers, these seem like the personality traits of a borderline sociopath: ridden by anxiety, unable to feel contentment, and uninterested in the fate of others. Weber had no wish to condemn early capitalists for these traits, but his plumbing of the capitalist psyche revealed a type not terribly different from the bourgeois "eunuchs" found in Marx's early essays. There was, however, one feature of Protestant capitalism that could meliorate its more pathological features: the concept of stewardship. The religious capitalist who believed that he held his property and profits in trust for the Almighty was theoretically less likely to consider them his personal reward for his efforts and more likely to view them as communal assets that he should spend for a greater good - reinvesting them in the economy or spending them on charitable and educational enterprises. This was the attitude of Andrew Carnegie, who while treating his workers like dogs spent millions of dollars on ways to "help the aspiring to rise" libraries, museums, parks, and educational endowments. The robber baron who, after years of cutting throats and sweating his employees, finally curled up on his accumulated treasures like Smaug the Dragon, had no place in this moral scheme, though one suspects Ayn Rand and her followers would regard him as a laudable human being, Carnegie as a moralizing sap, and Weber as a bore.