Republicanism is the political tradition holding that free self-government exists to prevent any person or group from holding arbitrary power over others, and that liberty depends on dividing power, binding it with law, and cultivating citizens willing to defend the public good. It runs from the Roman Republic through Machiavelli's Florence and the Atlantic revolutions to a philosophical revival that began in the 1990s.
A favorite courtier at an absolute king's court can eat what he likes, marry as he likes, and speak as he likes — the king never once interferes. An old political tradition insists he is still not free, because the king could turn on him tomorrow with no one to stop him. Republicanism's whole two-thousand-year argument turns on that distinction: being left alone is not the same as being safe from someone else's arbitrary power.