NLP information?

An example of a principle of NLP is, "Multiple viewpoints are useful". This will not be true in every case, but as a generalization in any field, information gathered by considering many different people's points of view will usually be more complete or useful than information provided by just one source. It cannot be "proven", but it is often a useful working guide. Different practitioners may have slightly different versions of what they consider "principles", but in general there is a fairly high degree of commonality and universal agreement on those most central to NLP.