"IF, therefore, a multitude of free men is ordered by the ruler towards the common good of the multitude, that rulership will be right and just, as is suitable to free men. If, on the other hand, a rulership aims, not at the common good of the multitude, but at the private good of the ruler, it will be an unjust and perverted rulership. The Lord, therefore, threatens such rulers, saying by the mouth of Ezekiel: “Woe to the shepherds that feed themselves (seeking, that is, their own interest): should not the flocks be fed by the shepherd?” Shepherds indeed should seek the good of their flocks, and every ruler, the good of the multitude subject to him."
~St. Thomas Aquinas: On Kingship (De Regno), Book I, Chap. 2─Different Kinds of Rule.