Man’s capacity for justice makes democracy possible; but man’s inclination to injustice makes democracy necessary.

Reinhold Niebuhr (1892–1971), a leading American Protestant theologian and public intellectual, developed “Christian realism” in the interwar and early Cold War years as a critique of both utopian liberal optimism and cynical power politics. The line is commonly cited from his reflections on democratic government: democracy rests on a real (if limited) human ability to recognize justice and cooperate, yet it is required precisely because individuals and groups are also prone to self-interest, pride, and coercion. In this setting, democratic institutions—checks and balances, accountability, and the rule of law—are portrayed as practical safeguards against the predictable abuses of power that arise from human fallibility.

The aphorism turns on a paradox: democracy is feasible only because people can sometimes act justly, deliberate, and restrain themselves; but democracy is indispensable because people often do not. Niebuhr’s point is not that democracy perfects human nature, but that it is the least-worst political arrangement for morally mixed creatures. It channels competing interests through institutions that limit domination and correct injustice over time. The quote also rebukes naïve faith in virtue alone (which would make democracy unnecessary) and fatalistic distrust of virtue (which would make democracy impossible). It frames democratic governance as an ethical compromise grounded in realism about power.