Rousseau was the conscience of France, which rebelled against the negations and the bald emptiness of the materialistic and atheistic doctrines. By vindicating with fervid eloquence the participation of the whole man in the highest questions, in opposition to the one-sided illumination of the understanding, he became a pre-Kantian defender of the faith of practical reason. His emphatic summons aroused a loud and lasting echo, especially in Germany, in the hearts of Goethe, Kant, and Fichte.
In the contemporaries Spinoza and Locke, the two schools of modern philosophy, the Continental, starting from Descartes, and the English, which followed Bacon, had reached the extreme of divergence and opposition, Spinoza was a rationalistic pantheist, Locke, an empirical individualist. With Leibnitz a twofold approximation begins. As a rationalist he sides with Spinoza against Locke, as an individualist with Locke against Spinoza. But he not only separated rationalism from pantheism, but also qualified it by the recognition (which his historical tendencies had of themselves suggested to him) of a relative justification for empiricism, since he distinguished the factual truths of experience from the necessary truths of reason, gave to the former a noetical principle of their own, the principle of sufficient reason, and made sensation an indispensable step to thought.