He starts by introducing his out work in the army base. He mentioned use of an old British trail to determine whether any of the soldiers that attend the trail have the potential to be leader or not. The result did not come out good. As he rethinks the process, he come to the conclusion that their prediction was little better then blind guesses. Most importantly the knew it, but somehow their mind keeps believe that their prediction are valid. He has discovered his first cognitive fallacy. He calls this “illusion of validity”

He further explained what the illusion of validity is. He Mentioned when facing a difficult question people often answer an easier instead. The more coherence of the story is the more confidence it gives to people and made them believe that its right even its not.

Later on, He applied his personal life story to help readers understand it. He some of get the privilege to work with an investing company. With the access to the company database, he discovered that the year to year correlation are zero. Sums up, professional investor’s “educated guess” are nothing more then a blind guess.

When he presents his discover to the company, they did not doubt his research. However, They have to confidence to believe that with their professional skills profiting for the stock trade is difficult but not impossible. He calls this term the “illusion of skills.”

He indicates a general problem in the society. In his words “overconfident professionals sincerely believe they have expertise , act as experts and look like experts.”