Watts makes a direct attack against the foundation of what we call 'common sense.' He backs his assault with a bevy of studies, done by himself and others. It was interesting to note that we are really bad at making predictions... of any kind. Yet we think we are fantastic at it because so many things seem obvious to us, especially in hindsight. This is a common theme of the book.
Interesting tidbit: experts are generally not statistically significantly better than a non-expert crowd at making predictions.