Investment management is a judgment‐rich endeavor. The major components of managing an investment program—determining objectives, finding and exploiting opportunities, and evaluating the extent to which objectives have been achieved—all involve judgment as much as data. Judgments in turn are framed by one's system of beliefs about how the investment world works. Given this, it seems worthwhile to ponder where the beliefs come from, to assess their validity, and to attempt to improve them as opportunities exist to do so. This chapter discusses the importance of beliefs in investment management and suggests that active management of one's belief system can make one a better investor. It illustrates by example that beliefs can be a determining factor in investment decisions and strategy and discusses the unconscious aspect of beliefs, especially the role of culture in determining unconscious beliefs. The process through which a cultural perspective on beliefs can illuminate investment behavior that otherwise seems puzzling is discussed and some suggestions are presented on how to make beliefs more conscious and deliberate. An argument that a key part of evaluating an investment manager is assessing the manager's belief system is presented, and the role of belief systems in evaluating active investment managers is analyzed.