Where did this obsession with the individual agent come from?
One school of thought traces individualism to capitalism, urbanization, and the industrial economy. Marx of course was a leader of this school, and Marxists were always fulminating against bourgeois individualism. I suspect this is the line taken in most Western Civ classes.
But other scholars think that can't be the whole story. For one thing Japan has managed to achieve a high degree of modernity in most ways without embracing the extreme notions of individual agency prominent in the west. For another, many people see the rise of individualism happening much earlier than Marx allowed. In art and literature, especially, some people see individualism rampant in the Renaissance; Shakespeare's characters are often held up as models of modern thought and action.
If individualism was on the rise before capitalism, what was driving it? A growing school of historians points to Christianity. The basic idea is that medieval Christianity put its emphasis on the Christian's personal relationship with God, and on achieving a personal path to salvation, and that this inwardness pointed the way to individualism. Some theologians thought a Christian should be a stranger in this world, a pilgrim, whose mission was to sever worldly ties rather than to deepen them. This Chrstian alienation can be seen as the precursor of the alienation of the modern city dweller. Samuel Moyn has a little review essay on some of these historians in the Boston Review, which I recommend for the curious. Here he summarizes the ideas of French historian Marcel Gauchet:
For Gauchet, the secret lies in monotheism’s unique approach to God’s transcendence, which made the divine so otherworldly that man became more autonomous in consequence. Christianity in particular severed the monotheistic promise from terrestrial fulfillment in the Promised Land and inscribed it “in the soul’s inner recesses,” a step that, as Gauchet puts it, “[intensified] divine exteriority in relation to creation.” The same revolution that alienated individuals in relation to the world inadvertently prepared their independence from the divine and deprived politics of any sacred meaning. Siedentop observes that, as a matter of the history of language, the “individual” emerged more or less simultaneously with the “state.” Gauchet insists this is no accident, since the early modern kings who founded the absolutist state completed the long-term transition whereby secular political authority no longer incarnates the divine—that only Jesus could do—but represents the will of individuals. The social contract was thus born as authority in politics ultimately needed to come from the ground up, rather than heaven down.These questions are, of course, very difficult to answer in any definitive way. My own view is that industrialization is the essential background to individualism at our level, especially our economy of "jobs" that people get by themselves, rather than families or households that produce something together. But I suspect that this would not, in itself, be enough, and I wonder if Christian loneliness before God did play some sort of role.