The estimate of the value of the history of philosophy in general, given at the start, is the more true of the history of modern philosophy, since the movement introduced by the latter still goes on unfinished. We are still at work on the problems which were brought forward by Descartes, Locke, and Leibnitz, and which Kant gathered up into the critical or transcendental question. The present continues to be governed by the ideal of culture which Bacon proposed and Fichte exalted to a higher level; we all live under the unweakened spell of that view of the world which was developed in hostile opposition to Scholasticism, and through the enduring influence of those mighty geographical and scientific discoveries and religious reforms which marked the entrance of the modern period. It is true, indeed, that the transition brought about by Kant's noëtical and ethical revolution was of great significance,--more significant even than the Socratic period, with which we are fond of comparing it; much that was new was woven on, much of the old, weakened, broken, destroyed. And yet, if we take into account the historical after-influence of Cartesianism, we shall find that the thread was only knotted and twisted by Kantianism, not cut through. The continued power of the pre-Kantian modes of thought is shown by the fact that Spinoza has been revived in Fichte and Schelling, Leibnitz in Herbart and Hegel, the sensationalism of the French Illuminati in Feuerbach; and that even materialism, which had been struck down by the criticism of the reason (one would have thought forever), has again raised its head. Even that most narrow tendency of the early philosophy of the modern period, the apotheosis of cognition is,--in spite of the moralistic counter-movement of Kant and Fichte,--the controlling motive in the last of the great idealistic systems, while it also continues to exercise a marvelously powerful influence on the convictions of our Hegel-weary age, alike within the sphere of philosophy and (still more) without it. In view of the intimate relations between contemporary inquiry and the progress of thought since the beginning of the modern period, acquaintance with the latter, which it is the aim of this _History_ to facilitate, becomes a pressing duty. To study the history of philosophy since Descartes is to study the pre-conditions of contemporary philosophy.