Identify the kinds of agreement or disagreement most probably exhibited by the following pairs:

a. For that some should rule and others be ruled is a thing not only necessary, but expedient; from the hour of their birth, some are marked out for subjection, others for rule. . . . It is clear, then, that some men are by nature free, and others slaves, and that for these latter slavery is both expedient and right.

b. If there are some who are slaves by nature, the reason is that men were made slaves against nature. Force made the first slaves, and slavery, by degrading and corrupting its victims, perpetuated their bondage.