Machiavelli's best-known book Il Principe contains several maxims concerning politics. Instead of the more traditional target audience of a hereditary prince, it concentrates on the possibility of a "new prince". To retain power, the hereditary prince must carefully balance the interests of a variety of institutions to which the people are accustomed. By contrast, a new prince has the more difficult task in ruling: He must first stabilise his newfound power in order to build an enduring political structure. Machiavelli suggests that the social benefits of stability and security can be achieved in the face of moral corruption. Machiavelli believed that public and private morality had to be understood as two different things in order to rule well. As a result, a ruler must be concerned not only with reputation, but also must be positively willing to act immorally at the right times. Machiavelli believed as a ruler, it was better to be widely feared than to be greatly loved; A loved ruler retains authority by obligation while a feared leader rules by fear of punishment.[67] As a political theorist, Machiavelli emphasized the occasional need for the methodical exercise of brute force or deceit including extermination of entire noble families to head off any chance of a challenge to the prince's authority.

Scholars often note that Machiavelli glorifies instrumentality in state building, an approach embodied by the saying "The ends justify the means." This quote has been disputed and may not come from Niccolò Machiavelli or his writings. Violence may be necessary for the successful stabilisation of power and introduction of new legal institutions. Force may be used to eliminate political rivals, to coerce resistant populations, and to purge the community of other men strong enough of a character to rule, who will inevitably attempt to replace the ruler. Machiavelli has become infamous for such political advice, ensuring that he would be remembered in history through the adjective, "Machiavellian".