We all have a set of basic beliefs—a world view. Everyone is a philosopher in this way. In this chapter, our concern is to provide criteria that distinguish a good set of basic beliefs from a poor one. This seems overwhelming perhaps. But in fact, it is a natural process, and one that we are involved in all the time. Whenever we take action, form an opinion, or consider other's views, we are testing a belief system—either ours or someone else's. So our present task is to make explicit what we naturally do by providing a framework to assess world views.