Machiavelli
The Prince

2 Of Hereditary Monarchies
I will not here speak of republics, having already treated of them fully in another place. I will deal only with monarchies, and will discuss how the various kinds described above can be governed and maintained. In the accustomed to a reigning family is far less than in new monarchies; for it is sufficient not to transgress ancestral usages, and to adapt one’s self to unforeseen circumstances; in this way such a prince, if of ordinary assiduity, will always be able to maintain his position, unless some very exceptional and excessive force deprives him of it; and even if he be thus deprived, on the slightest mischance happening to the new occupier, he will be able to regain it.

We have in Italy the example of the Duke of Ferrara, who was able to withstand the assaults of the Venetians in 1484 and of Pope Julius in 1510, for no other reason than because of the antiquity of his family in that dominion. In as much as the legitimate prince has less cause and less necessity to give offense, it is only natural that he should be more loved; and, if no extraordinary vices make him hated, it is only reasonable for his subjects to be naturally attached to him, the memories and causes of innovations being forgotten in the long period over which his rule has extended; whereas one change always leaves the way prepared for the introduction of another.