Lotze's lectures ranged over a wide field: he delivered annually lectures on psychology and on logic (the latter including a survey of the entirety of philosophical research, "Encyclopädie der Philosophie"), then at longer intervals lectures on metaphysics, philosophy of nature, philosophy of art, philosophy of religion, rarely on history of philosophy and ethics. In these lectures he expounded his peculiar views in a stricter form, and during the last decade of his life he embodied the substance of those courses in his "System der Philosophie", of which only two volumes have appeared (vol. I "Logik", 1st ed., 1874, 2nd ed., 1880; vol. II "Metaphysik", 1879). The third and concluding volume, which was to treat in a more condensed form the principal problems of practical philosophy, of philosophy of art and religion, was not completed before his death.