A wise prince cannot, nor ought he to, keep faith when such observance may be turned against him, and when the reasons that caused him to pledge it exist no longer. If men were entirely good, this precept would not hold, but because they are bad and will not keep faith with you, you are not bound to observe it with them.
with a treaty or agreement
There are no principles; there are only events. There is no good and bad, there are only circumstances.
There is no moral absolute, and this leads us to situational ethics, which unfortunately is being taught in public schools all over America. This means that right and wrong is dependent upon the circumstances.
It is circumstance and proper measure that give an action its character, and make it either good or bad.
Circumstances dictate your set of values, your set of morals.
There are in life conjunctions of circumstances when the reproach that we are not Voltaires is least of all appropriate.
Necessity is mightier than the law.
To me this question whether liberty is a good or a bad thing appears as irrational as the question whether fire is a good or a bad thing. It is both good and bad according to time, place, and circumstance, and a complete answer to the question, In what cases is liberty good and in what cases is it bad? would involve not merely a universal history of mankind, but a complete solution of the problems which such a history would offer.
We must recognise that duty and morality vary under different circumstances; not that the man who resists evil is doing what is always and in itself wrong, but that in the different circumstances in which he is placed it may become even his duty to resist evil.