A political tradition, traceable from Roman Rome through the Italian city-republics, the English civil war theorists (Harrington, Milton, Sidney), Montesquieu, Rousseau, and the American founders, that defines liberty as non-domination — freedom from being subject to the arbitrary will of another — and understands political life as the active self-government of a virtuous citizenry. It is distinct from, though sometimes overlapping with, the liberal tradition it ran alongside and was eventually eclipsed by.
The scholarly revival of republicanism is a distinctive late-20th-century achievement. Historians (J.G.A. Pocock, Quentin Skinner, Gordon Wood) argued that the dominant framework of early modern and American founding-era politics was not proto-Lockean liberalism but a "classical republican" or "civic humanist" inheritance — worried about corruption, obsessed with civic virtue, attuned to the fragility of free institutions under standing armies, executive patronage, and luxurious commerce. Political philosophers (above all Philip Pettit) then developed this historical recovery into a contemporary theory.
The core theoretical claim is that freedom as non-interference (Berlin's "negative liberty") misses something crucial. A slave with a kind master enjoys non-interference but is still unfree: subject to the master's arbitrary power, dependent on his continued goodwill. True freedom requires non-domination — institutional guarantees that protect one from being subject to the arbitrary will of others. Republican freedom therefore requires more than the silent space around individuals; it requires active citizenship, strong rule of law, dispersed power, and social conditions (economic security, rough equality) that prevent relations of dependence.
Republicanism has obvious affinities with Michael Sandel's critique of procedural liberalism and with egalitarian critiques of workplace hierarchy. It remains the most articulate live alternative to both liberal neutrality and communitarian traditionalism.