By a faction, understand a number of citizens, whether amounting to a majority or minority of the whole, who are united and actuated by some common impulse of passion, or of interest, adverse to the rights of other citizens, or to the permanent and aggregate interests of the community.

Madison offers this definition in Federalist No. 10 (1787), written during the ratification debates over the proposed U.S. Constitution. Responding to Anti-Federalist fears that a stronger national government would threaten liberty, Madison argues that the chief danger to popular government is “faction”—groups driven by passion or self-interest that may sacrifice others’ rights or the public good. The essay contends that factions are inevitable in a free society because people differ in opinions and, especially, in property and economic interests. The Constitution’s design—an extended republic with representative government—aims not to eliminate factions but to limit their harmful effects by making it harder for any one faction to dominate.

The definition frames faction as a moral and political problem: collective action becomes dangerous when it is “adverse” to others’ rights or to the community’s long-term welfare. Madison’s emphasis on both majority and minority factions is crucial—tyranny can arise not only from elites but also from popular majorities acting on passion. The quote also signals his realist premise that politics is driven by interests as much as ideals. Rather than relying on civic virtue alone, Madison proposes institutional remedies: representation, a large republic, and a multiplicity of competing interests. The passage remains central to modern discussions of pluralism, polarization, and how constitutional structures channel conflict.

1) “By a faction, I understand a number of citizens…”
2) “…united and actuated by some common impulse of passion, or of interest…”
3) “…adverse to the rights of other citizens, or to the permanent and aggregate interests of the community.”