For the circumstances of political rule are such that moral viciousness can never be excluded from the realm of possible actions in which the prince may have to engage. Machiavelli's sense of what it is to be a person of virtù can thus be summarized by his recommendation that the prince above all else must acquire a “flexible disposition.”
That ruler is best suited for office, on Machiavelli's account, who is capable of varying her/his conduct from good to evil and back again “as fortune and circumstances dictate”