What's required for motivation by principle?

Kant claimed both that "moral feeling is the capacity to be affected by a moral judgment" and that moral motivation is motivation by principle. What are the psychological mechanism(s) that could enable principles to motivate? This chapter develops in more detail a suggestion made elsewhere by the author that posits a connection between susceptibility to the discomfort of cognitive dissonance and moral motivation of a broadly Kantian kind. The chapter argues that the possession of principles is constitutively connected to one’s status as a diachronic self and to one’s rational agentive capacities. If psychopaths are insensitive to cognitive dissonance, they cannot have or be motivated by principles. This provides an explanation of the failure of moral motivation in psychopaths that differs from the usual focus on lack of empathy.