There is no freedom.
There is only the trembling difference between the slavery we are forced into and the service we choose.
When the barbarians arrive in the city he locks himself into a bare cell, renounces all his former happiness, denies the enemy by denying himself.
"So they will not envy me", he says, "so they will leave me alone."
This is how he lives for years - in a prison of his own devising, in a paradox of triumph achieved through self-defeat.
Until he is no longer sure whether he is a free man pretending to be a prisoner, or a prisoner imagining that he is free.