Since the appearance of Eduard Zeller's _Grundriss der Geschichte der griechischen Philosophie_ (1883; 3d ed. 1889) the need has become even more apparent than before for a presentation of the history of modern philosophy which should be correspondingly compact and correspondingly available for purposes of instruction. It would have been an ambitious undertaking to attempt to supply a counterpart to the compendium of this honored scholar, with its clear and simple summation of the results of his much admired five volumes on Greek philosophy; and it has been only in regard to practical utility and careful consideration of the needs of students--concerning which we have enjoyed opportunity for gaining accurate information in the review exercises regularly held in this university--that we have ventured to hope that we might not fall too far short of his example. The predominantly practical aim of this _History_--it is intended to serve as an aid in introductory work, in reviewing, and as a substitute for dictations in academical lectures, as well as to be a guide for the wider circle of cultivated readers--has enjoined self-restraint in the development of personal views and the limitation of critical reflections in favor of objective presentation. It is only now and then that critical hints have been given. In the discussion of phenomena of minor importance it has been impossible to avoid the _oratio obliqua_ of exposition; but, wherever practicable, we have let the philosophers themselves develop their doctrines and reasons, not so much by literal quotations from their works, as by free, condensed reproductions of their leading ideas. If the principiant view of the forces which control the history of philosophy, and of the progress of modern philosophy, expressed in the Introduction and in the Retrospect at the end of the book, have not been everywhere verified in detail from the historical facts, this is due in part to the limits, in part to the pedagogical aim, of the work. Thus, in particular, more space has for pedagogical reasons been devoted to the "psychological" explanation of systems, as being more popular, than in our opinion its intrinsic importance would entitle it to demand. To satisfy every one in the choice of subjects and in the extent of the discussion is impossible; but our hope is that those who would have preferred a guide of this sort to be entirely different will not prove too numerous. In the classification of movements and schools, and in the arrangement of the contents of the various systems, it has not been our aim to deviate at all hazards from previous accounts; and as little to leave unutilized the benefits accruing to later comers from the distinguished achievements of earlier workers in the field. In particular we acknowledge with gratitude the assistance derived from the renewed study of the works on the subject by Kuno Fischer, J.E. Erdmann,