William James made many references to pluralism throughout his career. Interestingly, many contemporary psychologists also discuss pluralism and indeed call for pluralism as a corrective to the discipline's philosophical and methodological foundations. Yet, pluralism and the purposes to which it is applied are understood in a variety of ways, and the relation of contemporary pluralism to the pluralism(s) of William James is uncertain. This book offers conceptual clarification in both contexts, first distinguishing diverse senses of pluralism in psychology and then systematically examining different forms of pluralism across the writings of James. A comparison of meanings and analysis of implications follows, aimed at illuminating what is at stake in ongoing calls for pluralism in psychology.