Thomas Aquinas is a towering figure in Christian medieval thought. In his work, On Kingship, he presents a defense of the monarchical system of government. He begins by asserting that “it is natural for man, more than for any other animal, to be a social and political animal.” Though this claim is not immediately apparent, Aquinas gives little justification for it. Hobbes and Rousseau both disagree with him, instead positing that men require a social contract in order to live in society. They both believe that society does not come about naturally. But instead of defending his claim, Aquinas merely says, “This is clearly a necessity of man’s nature.” As Aquinas frequently refers to Aristotle in his other works, it is possible that he is relying on Aristotle’s famous conclusion that “man is by nature a political animal” and does not feel that it is necessary to give his own justification. Another possibility is that he takes it as a natural conclusion to God’s statement in Genesis 1 that “It is not good for man to be alone.” After Aquinas declares that man is political by nature, he extrapolates several benefits that man receives through his political nature, such as having access to each other’s discoveries. However, these are not justifications for his claim, but rather conclusions drawn from his claim.
From this starting point, Aquinas observes that “it is necessary that there exist among men some means by which the group may be governed.” Men are by nature political, so they need some form of government to give structure to their natural associations. The question becomes, what is the optimal form of government? To answer this question, Aquinas makes an appeal to nature. He says, “Whatever is in accord with nature is best, for in all things nature does what is best.” Taking the perfection of nature as an assumption, he then notes that all groups in nature are governed by one thing, whether that thing is a single entity or a single principle; “Every natural governance is a governance by one.” As examples he cites the heart as the “principal mover” of the body, reason as the presider of the soul, a single “king bee” ruling the bees, and God as the ultimate power over the universe. The government of man ought to imitate the government of nature, so men ought to be governed by a single person. Therefore, he concludes, monarchy is the best form of government.
Aquinas then notes that because monarchy means government by a single person, it is the most unified form of government. This unity causes it to be the form of government that is most able to bring about what it desires. This is a positive benefit to the society it governs when the ruler is just. But Aquinas points out that this is a harmful attribute when the ruler in unjust; “A force operating for evil is more harmful when it is one than when it is divided.” For this reason, the less unified an evil government is, the better it will be for society. Democracies are the least unified form of government, thus they are the least efficacious. Therefore, among the unjust governments, democracies are the least harmful. In this sense, they are the least dangerous. If they are just, they will not be great, but if they are unjust, they will not be terrible. Monarchies, on the other hand, are very beneficial if they are just, and very harmful if they are unjust.
Though monarchies are the most tyrannical form of government when they become unjust, Aquinas persists in defending them because he believes that he has shown that they are the form of government most closely conforming to nature. But since he has also shown that monarchy can become the most harmful form of tyranny, he must consider the possibility of an evil king. What are the citizens to do should such a king arise? He first weighs the extent of the king’s tyranny. He says that if it is not too horrible, it is best to do nothing and bear it for a time. This is because it is dangerous to usurp a tyrant, as a failed attempt might only make matters worse; “It may happen that those who act against the tyrant are unable to prevail and the tyrant will rage the more.” If, however, the king becomes unbearably tyrannical, Aquinas affirms that the people have a right to remove him from office. This is because the people put him in place with a covenant specifying that he would act faithfully to the office of king. Since he did not fulfill his end of the covenant, the people have no obligation to be faithful to him as their king. Though Aquinas disagrees that the social contract is the basis for political organization, his idea of a covenant between king and subject could be seen as a precursor to Enlightenment social contract theory.
Aquinas affirms the right to resist an evil king, but he does so with caution. When the king’s subjects decide to remove him, they should not do it as private citizens, but “by public authority.” He does not detail precisely what he means by this, but he is attempting to protect against the rash and unneeded actions of a few. By specifying that a revolution against the king is only permissible if it is done by public authority, it ensures that there is just cause in removing the king.