In the quote, The purpose of psychology is to give us an entirely fresh viewpoint about things we know best, Paul Valery is basically saying that psychology gives people the ability to analyze themselves and the people and things closest to them from another perspective. For example, it can help a person who is terribly afraid of dogs to realize what factor of their past made them so afraid rather than thinking that dogs are just evil and vicious.
[...] An evolutionary psychologist would argue that perhaps the person felt as though telling the truth would make them weaker which would lessen their chances of survival. A socio-culturalist may argue that the person is being just merely influenced by the people and places that they are surrounded by. For example, the individual may come from a family that believed that telling a lie is viable so long as it poses no threat to others. A theory is an explanation based on observations or reasoning. [...]
using our reader.