The idealism of Berkeley, as was to be expected from the nature of the case, remained without any farther development, but the philosophy of Leibnitz was taken up and subjected to a farther revision by Christian Wolff. He was born in Breslau in 1679. He was chosen professor at Halle, where he became obnoxious to the charge of teaching a doctrine at variance with the Scriptures, and drew upon himself such a violent opposition from the theologians of the university, that a cabinet order was issued for his dismissal on the 8th of November, 1723, and he was enjoined to leave Prussia within forty-eight hours on pain of being hung. He then became professor in Marburg, but was afterwards recalled to Prussia by Frederic II. immediately upon his accession to the throne. He was subsequently made baron, and died 1754. In his chief thoughts he followed Leibnitz, a connection which he himself admitted, though he protested against the identification of his philosophy with that of Leibnitz, and objected to the name, Philosophia Leibnitio-Wolffiana, which was taken by his disciple Bilfinger. The historical merit of Wolff is threefold. First, and most important, he laid claim again to the whole domain of knowledge in the name of philosophy, and sought again to build up a systematic framework, and make an encyclopedia of philosophy in the highest sense of the word. Though he did not himself furnish much new material for this purpose, yet he carefully elaborated and arranged that which he found at hand. Secondly, he made again the philosophical method as such, an object of attention. His own method is, indeed, an external one as to its content, namely, the mathematical or the mathematico-syllogistical, recommended by Leibnitz, and by the application of this his whole philosophizing sinks to a level formalism. (For instance, in his principles of architecture, the eighth proposition is—“a window must be wide enough for two persons to recline together conveniently,”—a proposition which is thus proved: “we are more frequently accustomed to recline and look out at a window in company with another person than alone, and hence, since the builder of the house should satisfy the owner in every respect (§ 1), he must make a window wide enough for two persons conveniently to recline within it at the same time”.) Still this formalism is not without its advantage, for it subjects the philosophical content to a logical treatment. Thirdly, Wolff has taught philosophy to speak German, an art which it has not since forgotten. Next to Leibnitz, he is entitled to the merit of having made the German language for ever the organ of philosophy.

The following remarks will suffice for the content and the scientific classification of Wolff’s philosophy. He defines philosophy to be the science of the possible as such. But that is possible which contains no contradiction. Wolff defends this definition against the charge of presuming too much. It is not affirmed, he says, with this definition that either he or any other philosopher knows every thing which is possible. The definition only claims for philosophy the whole province of human knowledge, and it is certainly proper that philosophy should be described according to the highest perfection which it can attain, even though it has not yet actually reached it.—In what parts now does this science of the possible consist? Resting on the perception that there are within the soul two faculties, one of knowing and one of willing, Wolff divides philosophy into two great parts, theoretical philosophy (an expression, however, which first appears among his followers), or metaphysics, and practical philosophy. Logic precedes both as a preliminary training for philosophical study. Metaphysics are still farther divided by Wolff into ontology, cosmology, psychology, and natural theology; practical philosophy he divides into ethics, whose object is man as man; economics, whose object is man as a member of the family; and politics, whose object is man as a citizen of the state.

1. Ontology is the first part of Wolff’s metaphysics. Ontology treats of what are now called categories, or those fundamental conceptions which are applied to every object, and must therefore at the outset be investigated. Aristotle had already furnished a table of categories, but he had derived them wholly empirically. It is not much better with the ontology of Wolff; it is laid out like a philosophical dictionary. At its head he places the principle of contradiction, viz.: it is not possible for any thing to be, and at the same time not to be. The conception of the possible at once follows from this principle. That is possible which contains no contradiction. That is necessary, the opposite of which contradicts itself, and that is accidental, the opposite of which is possible. Every thing which is possible is a thing, though only an imaginary one; that which neither is, nor is possible, is nothing. When many things together compose a thing, this is a whole, and the individual things comprehended by it are its parts. The greatness of a thing consists in the multitude of its parts. If A contains that by which we can understand the being of B, then that in A by which B becomes understood is the ground of B, and the whole A which contains the ground of B is its cause. That which contains the ground of its properties is the essence of a thing. Space is the arrangement of things which exist conjointly. Place is the determinate way in which a thing exists in conjunction with others. Movement is change of place. Time is the arrangement of that which exists successively, etc.

2. Cosmology.—Wolff defines the world to be a series of changing objects, which exist conjointly and successively, but which are so connected together that one ever contains the ground of the other. Things are connected in space and in time. By virtue of this universal connection, the world is one united whole; the essence of the world consists in the manner of its connection. But this manner cannot be changed. It can neither receive any new ingredients nor lose any of those it possesses. From the essence of the world spring all its changes. In this respect the world is a machine. Events in the world are only hypothetically necessary in so far as previous events have had a certain character; they are accidental in so far as the world might have been directed otherwise. In respect to the question whether the world had a beginning in time, Wolff does not express himself explicitly. Since God is independent of time, but the world has been from eternity in time, the world therefore is in no case eternal in any sense like God. But according to Wolff, neither space nor time has any substantial being. Body is a connected thing composed of matter, and possessing a moving power within itself. The powers of a body taken together are called its nature, and the comprehension of all being is called nature in general. That which has its ground in the essence of the world is called natural, and that which has not, is supernatural, or a wonder. At the close of his cosmology, Wolff treats of the perfection and imperfection of the world. The perfection of a world consists in the harmony with each other of every thing which exists conjointly and successively. But since every thing has its separate rules, the individual must give up so much from its perfection as is necessary for the symmetry of the whole.

3. Rational Psychology.--The soul is that within us which is self-conscious. In the self-consciousness of the soul are itself and other objects. Consciousness is either clear or indistinct. Clear consciousness is thought. The soul is a simple incorporeal substance. There dwells within it a power to represent to itself a world. In this sense brutes also may have a soul, but a soul which possesses understanding and will is mind, and mind belongs alone to men. The soul of man is a mind joined to a body, and this is the distinction between men and superior spirits. The movements of the soul and of the body harmonize with each other by virtue of the preËstablished harmony. The freedom of the human soul is the power according to its own arbitrament, to choose of two possible things that which pleases it best. But the soul does not decide without motives, it ever chooses that which it holds to be the best. Thus the soul would seem impelled to its action by its representations, but the understanding is not constrained to its representations of that which is good and bad, and hence also the will is not constrained, but free. As a simple being the soul is indivisible, and hence incorruptible; the souls of brutes, however, have no understanding, and hence enjoy no conscious existence after death. This belongs alone to the human soul, and hence the human soul alone is immortal.

4. Natural Theology.—Wolff uses here the cosmological argument to demonstrate the existence of a God. God might have made different worlds, but has preferred the present one as the best. This world has been called into being by the will of God. His aim in its creation was the manifestation of his own perfection. Evil in the world does not spring from the Divine will, but from the limited being of human things. God permits it only as a means of good.

This brief aphoristic exposition of Wolff’s metaphysics, shows how greatly it is related to the doctrine of Leibnitz. The latter, however, loses much of its speculative profoundness by the abstract and logical treatment it receives in the hands of Wolff. For the most part, the specific elements of the monadology remain in the background; with Wolff, his simple beings are not representative like the Monads, but more like the Atoms. Hence there is with him much that is illogical and contradictory. His peculiar merit in metaphysics is ontology, which he has elaborated far more strictly than his predecessors. A multitude of philosophical terminations owe to him their origin, and their introduction into philosophical language.

The philosophy of Wolff, comprehensible and distinct as it was, and by its composition in the German language more accessible than that of Leibnitz, soon became the popular philosophy, and gained an extensive influence. Among the names which deserve credit for their scientific treatment of it, we may mention ThÜmming, 1697-1728; Bilfinger, 1693-1750; Baumeister, 1708-1785; Baumgarten the esthetic, 1714-1762; and his scholar Meier, 1718-1777.