The concept of prudence is vital for the appropriate understanding of Machiavelli and Guicciardini`s texts, being used in order to qualify the good judgment, the ability to make fast decisions and the acute comprehension of the transformations of reality. The prudent men must also be capable of articulating the products of the careful analysis of the reality`s movements in texts composed according to the precepts established in classical treatises of rhetoric. Thus one institutes two distinct, however mutually dependent, horizons concerning prudence. On the one hand, the emphasis on the calculation and measure of the things of the world - the possible results of the actions of governors and the other agents responsible for taking decisions in Republics, Principalities, Kingdoms or Papal States. On the other hand, the representation of prudence`s literate performance in texts composed according to the ethical and rhetorical and poetical rules established by the tradition. This thesis discusses this double character associated to prudence, especially through the exam of the histories composed by Machiavelli and Guicciardini.