On KingshipThomas Aquinas

Written around 1267 for the King of Cyprus, On Kingship is Aquinas's most direct treatment of political authority. He argues that monarchy is the best form of government because unity of rule best secures the common good, just as the body is best governed by one soul and the universe by one God. But the best form is also the most dangerous: monarchy corrupted becomes tyranny, which Aquinas calls the worst of all regimes precisely because concentrated power turned to private ends destroys public life most thoroughly.

The practical consequence is that political architecture must restrain the king's power. Aquinas recommends mixed government, blending monarchy with elements of aristocracy and popular consent, so that the ruler governs under law rather than above it. Tyrannicide he treats cautiously; private killing of a tyrant risks disorder worse than the tyranny itself, but public deposition by lawful authority can be legitimate.

The work applies Aristotelian political theory within a theological framework. The king's office exists to lead subjects toward the good life, but the good life itself is ordered toward a supernatural end that exceeds political competence. The priest, not the king, presides over that higher end. Aquinas thus limits political authority from above as well as from below: the state serves temporal welfare, but temporal welfare is not the final aim of human existence.