The passage discusses different types of thinking. It distinguishes between reverie, which involves spontaneous thoughts that often circle around the self, decision making, which requires choosing between options, and reasoning about beliefs when they are challenged. It notes that we are attached to our beliefs and opinions and tend to seek arguments to support positions we already hold rather than honestly examining where views originate. The thesis is that philosophers often fail to account for types of thinking like reverie in their theories and speculations, making their conclusions unrealistic.