The main emphasis in the recent development of mathematical finance has been in the pricing of derivative securities with the watershed moment being the now famous paper by Black and Scholes in 1973.  Of course, the price determined for a derivative is entirely dependent upon the model that is chosen for the underlying security.  Currently such models treat the market as an unthinking entity, changing according to some chance mechanism.  The purchase or sale of a derivative is then seen as the lone buyer/seller taking an action and the market producing an outcome.  However, the market exists only because of the buyers and sellers who enter into it.  The actions and outcomes of the players in the market are interdependent.  In this light, a more reasonable model of the market would be a many person game.