Abstract
The phenomenology of Multiple Personality (MP) syndrome is used to derive an Aristotelian explanation of the failure to achieve rational integration of mental content. An MP subject is best understood as having failed to master the techniques of integrating conative and cognitive aspects of her mental life. This suggests that in irrationality the subject may lack similar skills basic to the proper articulation and use of mental content in belief formation and control of action. The view that emerges centres mind on the activity of a subject rather than a structured causal nexus.