Niccolo Machavelli

Niccolò Machiavelli offered a famously dim view of human nature in The Prince. People are so "ungrateful, fickle, [and] false," he wrote, that a ruler should comfortably abandon conventional morality in dealing with them. He should slay deposed rulers and their families, recognize that friendship "yields nothing," and, beneath a veneer of compassion and honesty, master treachery and deceit. In short, because man is evil, leaders must know "how to do evil."