 John applies his principle that virtue is by definition a mean between excess and deficiency emphatically to the ruler. The moral qualities of the community as a whole are inextricable linked, in John’s view, to the moral characteristics of its royal head. By dint of his personal character, the good prince—the king—assures the coherence and well-being of the polity he rules; by contrast, a vicious prince—the tyrant—will reduce his subjects to slaves of his own private desires. Given the definition of virtue that John posits, the actions of a king must themselves and by definition be moderate. According to the Policraticus, the moderation exercised by the good ruler necessarily unifies and balances the relationship that his people enjoy with one another. Employing a musical metaphor, he asks,