The most cogent reason for restricting the interference of government is the great evil of adding unnecessarily to its power.

Mill’s point is that the case for limiting government is not only about efficiency or individual convenience, but about the structural danger of power itself. Even well-intended interventions can expand the state’s reach, normalize coercive tools, and create precedents that future officials may use for less benign ends. The “great evil” is thus cumulative: each unnecessary act of governance can increase the capacity and habit of interference, making citizens more dependent and officials more authoritative. The quote reflects Mill’s broader liberal concern with safeguarding individuality and preventing the concentration of social and political power that can stifle dissent and self-development.