Niccolo Machiavelli on Ambition from Wisdom-of-the-Wise.com

"For whenever men are not obliged to fight from necessity, they fight from ambition; which is so powerful in human breasts, that it never leaves them no matter to what rank they rise. The reason is that nature has so created men that they are able to desire everything but are not able to attain everything: so that the desire being always greater than the acquisition, there results discontent with the possession and little satisfaction to themselves from it. From this arises the changes in their fortunes; for as men desire, some to have more, some in fear of losing their acquisition, there ensues enmity and war, from which results the ruin of that province and the elevation of another."