The Prince by Niccolo Machiavelli Chapter 18 Page 3

hurtful to him and the causes which led him to pledge it are removed. If all men were good, this would not be good advice, but since they are dishonest and do not keep faith with you, you in return, need not keep faith with them; and no prince was ever at a loss for plausible reasons to cloak a breach of faith. Of this numberless recent instances could be given, and it might be shown how many solemn treaties and engagements have been rendered inoperative and idle through want of faith in Princes, and that he who was best known to play the fox has had the best success.

It is necessary, indeed, to put a good colour on this nature, and to be skilful in simulating and dissembling. But men are so simple, and governed so absolutely by their present needs, that he who wishes to deceive will never fail in finding willing dupes.