This article analyses the 'politics of humanity' in Cicero's philosophical and rhetorical works, the practice of projecting and shifting the moral and political boundary that separates the 'human' from the 'inhuman', the 'inept at being human', and the 'undeserving of being human'. This practice has many affinities with the relatively modern phenomenon of 'dehumanisation'. In the first part, the emphasis is on Cicero's humanism, in particular his ideas on human nature as they appear in De Officiis. Here I also show the impact of this practice on Roman ideas of self-fashioning, 'sincerity' and social performance. In the second part, I observe the way in which Cicero's political and legal theory fits within this ideological project. I further argue that Cicero's humanism provided a conceptual background to the rhetorical dehumanisation of his political enemies, that is, to the claims in his invective that these men could no longer be considered as proper human beings. My final suggestion is that the goal of this practice, at least some of the time, was to make a case for excluding these individuals from the state's legal system and thus depriving them of its protections.