This paper shows how and why Machiavelli's republican ideas, mainly set out in Discourses on the First Ten Books of Titus Livius, contrast with the recommendations he offers to a monarchical ruler in The Prince. The author argues, however, that what may be considered as Machiavelli's most original contribution runs constantly and consistently throughout his work. In terms calculated to provoke scandal, Machiavelli proclaims an ethics belonging exclusively to the field of politics that justifies acts of deception and cruelty. For Machiavelli, the use of evil is not merely a fact, nor just a political necessity, but also advisable for politics to function properly. The author attempts to show that this concept of political ethics boils down to what is ultimately an eminently political value: glory. He argues, however, that seeing glory as an end in itself, encompassing every type of regime, does not make republican principles the same as the aims of a principality. Thus, the dissonance between Machiavelli's main writings persists, but its terms are clarified.