M. Tullius Cicero, De Officiis
Walter Miller, Ed.

[26] The great majority of people, however, when they fall a prey to ambition for either military or civil authority, are carried away by it so completely that they quite lose sight of the claims of justice. For Ennius says:

There is no fellowship inviolate,
No faith is kept, when kingship is concerned;

and the truth of his words has an uncommonly wide application. For whenever a situation is of such a nature that not more than one can hold preeminence in it, competition for it usually becomes so keen that it is an extremely difficult matter to maintain a “fellowship inviolate.” We saw this¹ proved but now in the effrontery of Gaius Caesar, who, to gain that sovereign power which by a depraved imagination he had conceived in his fancy, trod underfoot all laws of gods and men. But the trouble about this matter is that it is in the greatest souls and in the most brilliant geniuses that we usually find ambitions for civil and military authority, for power, and for glory, springing up; and therefore we must be the more heedful not to go wrong in that direction.