In The Prince (Penguin: 1981), Machiavelli (1469-1527) wrote:
“There are two things a prince must fear: internal subversion from his subjects; and external aggression by foreign powers. Against the latter, his defense lies in being well-armed and having good allies; and if he is well armed he will always have good allies….Now, as far as his subjects are concerned, when there is no disturbance abroad the prince’s chief fear must be a secret conspiracy. He can adequately guard against this if he avoids being hated or scorned and keeps the people satisfied: this, as I said above at length, is crucial. One of the most powerful safeguards a prince can have against conspiracies is to avoid being hated by the populace.” (p. 103)
But Plato (427-347), in his Republic, points out a third thing a prince must fear: himself. More specifically, he must fear becoming a tyrant with an unjust soul or a soul in which the appetites for physical pleasure usurp reason and shame leading to an internal state of conflict, enslavement, and madness. Here we have Socrates pointing out to Glaucon how the soul of a tyrant is analogous to the conditions under a political tyranny (translation by Francis Cornford):
“Socrates: If the individual, then, is analogous to the state, we shall find the same order of things in him: a soul labouring under the meanest servitude, the best elements in it being enslaved, while a small part, which is also the most frenzied and corrupt, plays the master. Would you call such a condition of the soul freedom or slavery?
Glaucon: Slavery, of course.
Socrates: And just as a state enslaved to a tyrant cannot do what it really wishes, so neither can a soul under a similar tyranny do what it wishes as a whole. Goaded on against its will by the sting of desire, it will be filled with confusion and remorse. Like the corresponding state, it must always be poverty-stricken, unsatisfied, and haunted by fear. Nowhere else will there be so much lamentation, groaning, and anguish as in a country under a despotism, and in a soul maddened by the tyranny of passion and lust.”
If this psychological account is correct, then Machiavelli’s analysis of the two sources of fear for the prince contains a dangerous oversight. For should a prince develop an unjust soul he will make irrational judgments which will make internal conspiracy and external aggression unavoidable. As Socrates points out, the tyrant will experience internal fear from “his servants who will make away with him and his family” and external fear from “his neighbors who will not tolerate the claims of one man to lord it over others.” So any would-be prince should, besides reading The Prince, also follow Socrates’ advice to found a just republic in himself where reason and the love of wisdom control the soul’s other powers. Only then can political flourishing become a reality.