On one standard reading, Plato's works contain at least two distinct views about the structure of the human soul. According to the first, there is a crucial unity to human psychology: there is a dominant faculty that is capable of controlling attention and behaviour in a way that not only produces right action, but also ‘silences’ inclinations to the contrary—at least in idealized circumstances. According to the second, the human soul contains multiple autonomous parts, and although one of them, reason, normatively dominates the others, it may fail to do so descriptively: even in the face of full, explicit, well-reasoned, conscious awareness of the truth of a claim, a person may continue to feel residual inclinations towards disavowed, inappropriate and misguided experiences and courses of action. In this paper, I will argue that even the second of these views does not fully capture the ways in which reflective commitment fails to guide human action. Whereas the traditional multi-part soul view is well suited to explaining phenomena that involve a cognitive conflict between our reflective attitudes and our non-reflective endorsements (such as weakness of the will), it falls short when we turn to the full array of human patterns of response, because it neglects a further source of challenge to reason's rule, namely, the mediation of associative and heuristic processes. These processes introduce complications for which the simple faculty psychology view cannot adequately account. Because they produce challenges to reason's rule that are phenomenologically invisible, traditional strategies for self-regulation cannot be straightforwardly applied to their management.