This chapter lays out ten interrelated arguments about the purposes of history for contemporary psychology. These reasons are put forward here both as an introduction to the present volume and as arguments in their own right. All are present, but scattered and often enough implicit rather than spelt out, in the existing literature. These arguments constitute reasons why history has, or might have, or should have significance for psychologists. It may be helpful for further discussion to have reasons such as fostering disciplinary identity, perspective, critique, advancing unifying theory, doing justice to the historical content of knowledge, and so on, expressed in a systematic (if not comprehensive) way. At the heart of the reasons are, first, philosophical questions about the nature of scientific knowledge, the proper subject matters of psychology, and the authority of current approaches as science, and, second, practical, organizational, and social policy questions about the resources committed to psychology or, more precisely, distributed among the different domains of psychological activity. Most of the reasons speak to the world of psychologists, but the author, a historian of science and not a psychologist, argues that the deeper issues at stake, to do with the nature of psychology as science, raise wider questions about being human and the purposes for which knowledge is a goal at all.