The thought of being under absolute compulsion, the plaything of another, is unendurable for a human being. Hence, if every way of escape from the constraint is taken from him, there is nothing left for him to do but to persuade himself that he does the things he is forced to do willingly, that is to say, to substitute devotion for obedience. … It is by this twist that slavery debases the soul: this devotion is in fact based on a lie, since the reasons for it cannot bear investigation. … Moreover, the master is deceived too by the fallacy of devotion.

Gravity and Grace (1972), pp. 142-143