In Politics III, 4.1277a15–16 Aristotle presents phronēsis as the characteristic excellence of the good ruler. Difficulties arise when we consider that, on his view, a good ruler should always be loyal to his constitution, even when its prescriptions are contrary to moral goodness. This paper investigates the condition of a wise ruler in imperfect communities by attempting to answer the following questions: Would a wise ruler be capable of retaining his practical wisdom in a deviant community and stay loyal to (...) the constitution? Can the quality of any deviant polis be improved by the ruler’s practical wisdom without losing its distinctive nature? It is argued that Aristotle believes in the possibility of improving a deviant constitution compatibly with its preservation, and that such a possibility does not undermine the ruler’s practical wisdom. The only one constitution that leaves this possibility open is the polity. (shrink)