A prince... must learn from the fox and the lion... One must be a fox in order to recognize traps, and a lion to frighten off wolves. Those who act simply as lions are stupid. So it follows that a prudent ruler cannot, and must not, honour his word when it places him at a disadvantage and when the reasons for which he made his promise no longer exist.
Niccolo MachiavelliAnd if such malignity is hidden for a time, it proceeds from the unknown reason that would not be known because the experience of the contrary had not been seen, but time, which is said to be the father of every truth, will cause it to be discovered.
Niccolo MachiavelliAnd the prince who has relied solely on their words, without making other preparations, is ruined, for the friendship which is gained by purchase and not through grandeur and nobility of spirit is merited but is not secured, and at times is not to be had.
Niccolo Machiavelli