Vice is often compared with bodily diseases in Plato's dialogues, as if bodily diseases were an insightful scheme to understand how a psychic structure can be infected, contaminated, and then completely corrupted. But what is a strict analogy in the Republic seems to refer clearly to a causal interaction between body and soul in the Timaeus: vice can emerge from a malign disposition of the body, and, conversely, vice can cause or feed new bodily diseases in a disharmonious and neglected body. This paper argues that there is a consistent use of the analogy between vice and disease in the Republic and the Timaeus; the claim that psychic diseases are involuntary in the Timaeus is actually compatible with the agent's responsibility regarding his ethical and physical good condition, within a strong normative approach to diseases, both of the body and the soul.