This chapter explores Lipps’s psychology, his most basic field of investigation and the area of his work that is presupposed by all the others. First, I elaborate on the context of Lipps’s psychological thought and its evolution: I discuss the “post-Herbartian” mentalistic paradigm of psychology as it appeared, developed, and waned in German and Austria between the early nineteenth and early twentieth centuries, and the resulting process of the “psychologization” and “depsychologization” of knowledge. Second, I propose an in-depth analysis of Lipps’s reflections on the foundations of psychological science. As I demonstrate, between the years 1877–1880 and 1912 his psychological thought went through three major evolutionary stages. Third, I show that, far from simply being a philosopher-psychologist, Lipps was also recognized as an authentic “practitioner” of psychology who contributed to a vast array of specialized domains, even while maintaining an ambivalent position toward experimentalism. Fourth and last, I analyze at length Lipps’s affective psychology, which, along with empathy, represents his chief specific contribution to psychological science. After discussing elements of context, I trace the evolution of Lipps’s ideas on the psychological concept of feeling (Gefühl), insisting on its implications for his way of conceiving the ontology and phenomenology of affective states.