The philosophy that has helped me both in making money as a hedge fund manager and in spending it as a policy oriented philanthropist is not about money but about the complicated relationship between thinking and reality. The crash of 2008 has convinced me that it provides a valuable insight into the workings of the financial markets.
The efficient market hypothesis holds that financial markets tend towards equilibrium and accurately reflect all available information about the future. Deviations from equilibrium are caused by exogenous shocks and occur in a random manner. The crash of 2008 falsified this hypothesis.
I contend that financial markets always present a distorted picture of reality. Moreover, the mispricing of financial assets can affect the so-called fundamentals that the price of those assets is supposed to reflect. That is the principle of reflexivity.