The purpose of this volume is to reopen the discussion of how to develop the economic theory of investment to better model the facts of experience and to provide policy makers with a better understanding of how capital markets work. In this final decade of the twentieth century, almost everyone agrees that human progress will be closely related to the decisions regarding the investments made to promote economic growth of output. Despite the Nobel prize work done in recent decades, economic performance in this area seems to have worsened. Clearly, a reopening of public discussion on what is required is necessary. Until we get our theory right, it is impossible to get our public policy right. This book does not promise to provide "the" correct theory. Instead, it hopes to stimulate the reader into an understanding of where we may have gone wrong, and how we might rectify our mistakes.