The major focus of this work is on William James's insistence that unification should not be explored in the abstract as if it were one thing. Rather, unity should be understood in terms of its major kinds. There are unities and pluralities with respect to such topics as values, methods, causes, and prescriptions about what to read and study. This article explores James's mature position on unification as set forth in his major psychological and philosophical works and letters. (PsycInfo Database Record (c) 2024 APA, all rights reserved).