Wolff systematized the unordered and desultory doctrines of Leibnitz for the purpose of teaching them logically. This was in 1706, when by the aid of Leibnitz he obtained the professorship of mathematics at Halle. He met with instant success. The rationalism of his doctrine is seen from the title of many of his works, which are _Reasonable Thoughts on God_, _Reasonable Thoughts on the Powers of the Human Understanding_, etc. He lectured at Halle until 1723, when he was expelled by the theological influence. His return to Halle in 1740 was coincident with the crowning of Frederick the Great and the beginning of the German Enlightenment. We can note a few general aspects of his teaching. He employed the German language in his lectures, following Thomasius, who was the first to do it. Leibnitz had written in letters and treatises for the few, and had used either Latin or French. Wolff expanded Leibnitz’s doctrine, broadly and superficially, for a larger public, in the German tongue. He systematized Leibnitz’s teaching, and thereby could disseminate it. But in doing this he so toned down Leibnitz’s leading ideas that they lost all their peculiar force. For instance, he taught that only the human mind has the power of representation; and again, that preëstablished harmony applies only to the relation of the soul and body of the human monad. In general, he so extended the Leibnitz principle of sufficient reason that it applied to all departments, and was reduced to the principle of identity. The world is a huge mechanism designed for divine ends. Rationality is assumed to be everywhere, and knowledge of its existence is to be obtained only by deduction from evident principles. The result was that the philosophy of Leibnitz was reduced to a commonplace and empty rationalism――a purely deductive affair. Wolff undertook to demonstrate everything, and to make intelligible what is above reason. The Wolffian philosophy was a reversion to mediæval scholasticism, since it solved all problems by proof through the cogency of mathematical and logical processes. Truth is a matter of definition and classification. Thus Wolff produced a philosophy that was pedantic and formal, clear but shallow. It was Leibnitzian with Leibnitz omitted; it was a thorough-going dogmatism, because no problem was difficult to it; it was a rationalism, because to it all truth is the deliverance of the reason and none is derived from experience.