Though not read nearly as much as it should be, Montesquieu’s The Spirit of the Laws (1748) is a fundamental text in the history of political philosophy. Featuring key presentations of themes including the separation of powers, the effect of commerce in politics, and the nature of republican and monarchical governments, The Spirit of the Laws had profound influence on the founders and the Constitution—as well as on the school of political thought that came to be called modern liberalism. In this Conversation, Harvey Mansfield presents a powerfully illuminating introduction to Montesquieu’s great—though extremely challenging—work. He explains how Montesquieu opposed the idea of an unlimited concentration of power, a notion that came into the modern world especially through the teaching of Thomas Hobbes. In challenging it, however, Montesquieu does not try to return to Aristotle’s notion of a best regime, which, he implies, leads to imperialism. Rather, Montesquieu accepts the modern notion of power but turns it against itself through his doctrine of the separation of powers. As for the tendency toward imperialism, Montesquieu’s alternative is the commercial republic, which will inevitably try to expand but do so more peacefully. This is a must-see introduction to a work that can help us better understand both the United States and the modern world more generally.