And a parent who is worried about aspects of a teenage child's behavior and how the parent's actions might make a difference probably needs a behavioral approach. While each of the several approaches to personality psychology is quite good at handling its own key concerns, each also and rather disconcertingly tends to ignore the key concerns of all the other approaches. Doing one thing well, it seems, entails doing many other things poorly. For that reason, personality psychology needs to look at people from all of these directions and utilize all of these basic approaches. In the introduction to his novel, Mother Night, Kurt Vonnegut does his readers the unusual service of telling them the moral of the book they are about to read.
Great strengths are usually great weaknesses, and surprisingly often the opposite is true as well.
This first law applies to fields of research, to theories, and also to individual people. Personality psychology provides an excellent example of Funder's First Law. As has been noted already, personality psychology's biggest advantage over other areas of psychology is that it has a broad mandate to account for the psychology of whole persons and to be relevant to real-life concerns. This mandate makes the study of personality more inclusive, interesting, important, and even more fun than it would be otherwise. This mandate is also personality psychology's biggest problem.