5: John Nash (1928 - )

The award-winning film "A Beautiful Mind" popularized the story of John Nash. Nash is a world-renowned mathematician who struggled with paranoid schizophrenia after coming up with significant contributions to the concept of game theory. The idea of the "Nash Equilibrium," which discusses whether players in a game can benefit if one of them changes a strategy, can be applied to various fields, including economics. The U.S. Military even adopted tactics based off his ideas to use for the Cold War [source: Singh].

­Although the film (based on Sylvia Nasar's biography of the same name) takes liberties with the true story of Nash's life, he did experience hallucinations and delusions. His hallucinations included hearing voices, but not seeing people or things that weren't there. He began to have delusions of grandeur and believed that m­ajor world fig­ures were out to get him [source: PBS]. After spending about 30 years struggling with the disorder and spending time in and out of hospitals, he was able to make a significant recovery in the late 1980s. In 1994, John Nash received the Nobel Prize in Economic Sciences for his early work with game theory.

John Nash suggests that irrational thought actually has its benefits. Discussing his recovery from schizophrenia, Nash remarks that it is not "entirely a matter of joy" for him. He explains: "One aspect of this is that rationality of thought imposes a limit on a person's concept of his relation to the cosmos" [source: Nash].

Learn about other mad geniuses on the next page.