Where the argument is set
Book I of Plato's Republic opens the question in its starkest form. Thrasymachus is given the most provocative line of the dialogue: that justice is the interest of the stronger, and that the people most successful at being unjust are the ones the city honours and the ones the rest of us secretly envy.
It is a position the rest of the dialogue is constructed to refute. But it is not refuted by appealing to law, popularity, or consequences. Socrates' answer is that the tyrant — the figure Thrasymachus admires — is in fact the most miserable person in the city, because the soul that has unhooked itself from the disciplines of justice is at war with itself. The argument is about what unbounded power does to the person who holds it before it is about what it does to others.
The tyrant in Plato's eight and ninth
The Republic's analysis of the regimes (Books VIII–IX) tracks a slow decay from the city of speech down through timocracy, oligarchy and democracy to tyranny. At each step it is not the institutions but the soul that changes; and the tyrannical soul is the one in which appetite has become absolute, recognising no internal limit. The external position of the tyrant — with armed protection, with flatterers, with the routine destruction of any equal — is presented as the symptom of an internal collapse, not as the cause of one.
This is the classical inversion of the modern picture. Power without the disciplines of character is not so much a danger that can be restrained by external structures; it is, on Plato's reading, a deformation that has already happened, of which the external behaviour is the visible part.
Plutarch's negative cases
Plutarch's Parallel Lives are often read for their model statesmen, but they include their share of the opposite. The reader who works through the imperial Lives sees the same psychology Plato describes — appetite without check, suspicion without basis, the steady narrowing of who is permitted in the room — playing out across recognisable historical figures. Plutarch does not moralise. He observes. The lives reveal themselves.
Augustine's libido dominandi
The Christian tradition gives the worry one of its sharpest names. In the City of God, Augustine reads the long Roman story partly through the lens of libido dominandi — the lust for mastery — which he treats as the deforming root of much of the political behaviour the Roman historians had already documented. The vocabulary is Christian; the diagnosis is recognisably continuous with Plato's. Power without the orientation toward something beyond itself becomes its own project, and the project consumes the person.
What this commits us to
Two cautious claims follow.
First, external restraint on power is necessary but not sufficient. The classical analysis does not say that institutions are useless; it says that institutions cannot fully repair what unbounded power does to the person who holds it. Constitutional restraints do real work. But the people running the restraints are themselves either being shaped by power or shaping themselves against it.
Second, the question of virtue is not separable from the question of power. The companion essay, Virtue without power, makes the inverse claim from the other side: that virtue cut off from the political order can save the person but rarely the city. The two together state, roughly, the question the platform takes as its own.