This book introduces and assesses the main contributions of Hermann Lotze (1817-1881) to philosophy of psychology and philosophy of mind. Lotze was the most influential thinker of his time; he revitalised German philosophy after Hegel's death, inspiring American pragmatists as well as British idealists. He brought medical research, metaphysics, and psychology together in his work to argue for an approach to psychology in which the soul is central. Lotze defended the soul, the irreducibility of the mental, and the interaction between soul and body; in doing so, he proposed views of feeling, attention, self-consciousness, and the unity of consciousness. While Lotze's views were widely discussed at the end of the nineteenth and the beginning of the twentieth century, they are now unjustly neglected. In this volume, Mark Textor provides a rational reconstruction of Lotze's philosophy of psychology. He examines in detail Lotze's affective theory of self-consciousness and his account of comparing, the activity in which we attain awareness of relations. The latter fuels an original argument for the existence of the soul and its importance for psychology. This argument is also seen as a refutation of panpsychism, the view that fundamental reality is made of 'mind-stuff'. The book pays close attention to the historical background of Lotze's thought, as well as discussions of his work in American and British philosophy, and thereby sheds light on how his thought shaped American Pragmatism and British Idealism.