experience;
reason;
the ability, indeed the necessity, to learn from experience, instruction and reflection;
the ability to change their environment with hands and brain and thus to change themselves in the process (in fact, that is how we became human);
the ability to practice psychophysical disciplines of various kinds.
In Poul Anderson's Brain Wave, an increase in intelligence enables human reason to win its long war against animal instincts. Isaac Asimov's Daneel Olivaw reasons his way beyond the First Law of Robotics. (Daneel is an artificial, not a biological, intelligence but, by the same token, there are some parallels.)
So I think that some of the homo servus in SM Stirling's Drakon would be able, perhaps quite dispassionately, to reach the conclusion that the Domination, incapable of reform, should be overthrown - and they would be well placed to sabotage it.
