According to Kant, the opacity of human motivation takes two distinct forms – a psychological form: man ‘can never, even by the most strenuous self-examination, get entirely behind [his] covert incentives’ – and a social form: ‘everyone in our race finds it advisable to be on his guard, and not to reveal himself completely’. In other words, first, men's ‘interior’ cannot be entirely revealed to themselves and, second, they tend not to reveal their ‘interior’ to others. A number of Kant (...) scholars have acknowledged the importance of the first form of opacity in Kant's thought and have attempted to draw out from it implications for moral deliberation and ethics in general. The aim of this paper is to examine the second, social form of opacity and draw out its anthropological implications, an issue that has been overlooked in the literature. To do so, I focus on Kant's contrast between men and beings that I would like to call ‘sincere aliens’. These sincere aliens are beings who have the opposite features of man's opacity, namely beings who cannot but reveal their ‘interior’ both to others and to themselves. (shrink)