“If Trump is willing to negotiate on Principle is it really a principle?”
If you have more than one ‘principle’, then the ‘principles’ can be in conflict. Sometimes ‘principles’ must be balanced. Tradeoffs made. Negotiations done.
I understand what you are saying, but what I am saying is that for something to reach the level of principal, it would have to be very important and would form the basis of your worldview as a whole. When you are willing to negotiate on those principles then the aren’t principles they are beliefs.