It is perhaps in his _Theodicée_, in the treatment of the problem of evil, that his implicit Spinozism, or denial of individuality, comes out most clearly. That evil is negative, or privative, and consists in the finitude of the creature, is the result of the discussion. What is this except to assert the unreality, the merely privative character, of the finite, and to resolve all into God? To take one instance out of many: he compares inertia to the original limitation of creatures, and says that as inertia is the obstacle to the complete mobility of bodies, so privation, or lack, constitutes the essence of the imperfection, or evil, of creatures. His metaphor is of boats in the current of a river, where the heavier one goes more slowly, owing to inertia. The force of the current, which is the same to all, and which is positive, suffering no diminution, is comparable to the activity of God, which also is perfect and positive. As the current is the positive source of all the movements of the bodies, and is in no way responsible for the retardation of some boats, so God is the source only of activities,--the perfections of his creatures. "As the inertia of the boat is the cause of its slowness, so the limitations of its receptivity are the cause of the defects found in the action of creatures." Individuality is thus reduced to mere limitation; and the unlimited, the real which includes all reality, is God. We are thus placed in a double difficulty. This notion of an all-inclusive one contradicts the reality of mutually exclusive monads; and we have besides the characteristic difficulty of Spinoza,--how, on the basis of this unlimited, self-identical substance, to account for even the appearance of finitude, plurality and individuality. Leibniz's fundamental defect may thus be said to be that, while he realized, as no one before him had done, the importance of the conception of the _negative_, he was yet unable to grasp the significance of the negative, was led to interpret it as merely privative or defective, and thus, finally, to surrender the very idea. Had not his method, his presupposition regarding analytic identity, bound him so completely in its toils, his clear perception that it was the negative element that differentiated God from the universe, intelligence from matter, might have brought him to a general anticipation not only of Kant, but of Hegel. But instead of transforming his method by this conception of negation, he allowed his assumed (_i. e._, dogmatic) method to evacuate his conception of its significance. It was Hegel who was really sufficiently in earnest with the idea to read it into the very notion of intelligence as a constituent organic element, not as a mere outward and formal limitation.