As empiricism sprang from the striving to subject the intellectual to the material, to materialize the spiritual, so on the other hand, idealism had its source in the effort to spiritualize the material, or so to apprehend the conception of mind that matter could be subsumed under it. To the empiric-sensualistic direction, mind was nothing but refined matter, while to the idealistic direction matter was only degenerated (vergrÖbert) mind (“a confused notion,” as Leibnitz expresses it). The former, in its logical development, was driven to the principle that only material things exist, the latter (as with Leibnitz and Berkeley) comes to the opposite principle, that there are only souls and their ideas. For the partial realistic standpoint, material things were the truly substantial. But for the idealistic standpoint, the substantial belongs alone to the intellectual world, to the Egos. Mind, to the partial realism, was essentially void, a tabula rasa, its whole content came to it from the external world. But a partial idealism sought to carry out the principle that nothing can come into the mind which had not at least been preformed within it, that all its knowledge is furnished it by itself. According to the former view knowledge was a passive relation, according to the latter was it wholly active. While, in fine, a partial realism had attempted to explain the becoming in nature for the most part through real, i. e. through mechanical motives (l’homme machine is the title of one of la Mettrie’s writings), idealism had sought an explanation of the same through ideal motives, i. e. teleologically. While the former had made its prominent inquiry for moving causes, and had, indeed, often ridiculed the search for a final cause; it is final causes toward which the latter directs its chief aim. The mediation between mind and matter, between thought and being, will now be sought in the final cause, in the teleological harmony of all things (pre-established harmony). The standpoint of Leibnitz may thus be characterized in a word.

Gottfried Wilhelm Leibnitz was born in 1646, at Leipsic, where his father was professor. Having chosen the law as his profession, he entered the university in 1661, and in 1663 he defended for his degree of doctor in philosophy, his dissertation de principio individui, a theme well characteristic of the direction of his later philosophizing. He afterwards went to Jena, and subsequently to Altdorf, where he became doctor of laws. At Altdorf he was offered a professorship of jurisprudence, which he refused. The rest of his life was unsettled and desultory, spent for the most part in courts, where, as a versatile courtier, he was employed in the most varied duties of diplomacy. In the year 1672 he went to Paris, in order to induce Louis XIV. to undertake the conquest of Egypt. He subsequently visited London, whence he was afterwards called to Hanover, as councillor of the Duke of Brunswick. He received later a post as librarian at WolfenbÜttel, between which place and Hanover he spent the most of his subsequent life, though interrupted with numerous journeys to Vienna, Berlin, etc. He was intimately associated with the Prussian Electress, Maria Charlotte, a highly talented woman, who surrounded herself with a circle of the most distinguished scholars of the time, and for whom Liebnitz wrote, at her own request, his TheodicÉe. In 1701, after Prussia had become a kingdom, an academy was established at Berlin, through, his efforts, and he became its first president. Similar, but fruitless attempts were made by him to establish academies in Dresden and Vienna. In 1711 the title of imperial court councillor, and a baronage, was bestowed upon him by the emperor Charles VI. Soon after, he betook himself to Vienna, where he remained a considerable period, and wrote his Monadology, at the solicitation of Prince Eugene. He died in 1716. Next to Aristotle, Leibnitz was the most highly gifted scholar that had ever lived; with the richest and most extensive learning, he united the highest and most penetrating powers of mind. Germany has reason to be proud of him, since, after Jacob Boehme, he is the first philosopher of any note among the Germans. With him philosophy found a home in Germany. It is to be regretted that the great variety of his efforts and literary undertakings, together with his roving manner of life, prevented him from giving any connected exhibition of his philosophy. His views are for the most part developed only in brief and occasional writings and letters, composed frequently in the French language. It is hence not easy to state his philosophy in its internal connection, though none of his views are isolated, but all stand strictly connected with each other. The following are the chief points:

1. The Doctrine of Monads.—The fundamental peculiarity of Leibnitz’s theory is its opposition to Spinozism. Substance, as the indeterminate universal, was with Spinoza the only positive. With Leibnitz also the conception of substance lay at the basis of his philosophy, but his definition of it was entirely different. While Spinoza had sought to exclude from his substance every positive determination, and especially all acting, and had apprehended it simply as pure being, Leibnitz viewed it as living activity and active energy, an example for which might be found in a stretched bow, which moved and straightened itself through its own energy as soon as the external hindrance was removed. That this active energy forms the essence of substance is a principle to which Leibnitz ever returns, and from which, in fact, all the other chief points in his philosophy may be derived. From this there follow at the outset two determinations of substance directly opposed to Spinozism; first, that it is a single being, a monad; and second, that there are a multiplicity of monads. The first follows because substance, in so far as it exercises an activity similar to an elastic body, is essentially an excluding activity, or repulsion; the conception of an individual or a monad being that which excludes another from itself. The second follows because the existence of one monad involves the existence of many. The conception of one individual postulates other individuals, which stand over against the one as excluded from it. Hence the fundamental thesis of the Leibnitz philosophy in opposition to Spinozism is this, viz., there is a multiplicity of individual substances or monads.

2. The Monads more Accurately Determined.—The monads of Leibnitz are similar to atoms in their general features. Like these they are corpuscular units, independent of any external influence, and indestructible by any external power. But notwithstanding this similarity, there is an important and characteristic difference between the two. First, the atoms are not distinguished from each other, they are all qualitatively alike; but each one of the monads is different in quality from every other, every one is a peculiar world for itself, every one is different from every other. According to Leibnitz, there are no two things in the world which are exactly alike. Secondly, atoms can be considered as extended and divisible, but the monads are metaphysical points, and actually indivisible. Here, lest we should stumble at this proposition (for an aggregate of unextended monads can never give an extended world), we must take into consideration Leibnitz’s view of space, which, according to him, is not something real, but only confused, subjective representation. Thirdly, the monad is a representative being. With the atomists such a determination would amount to nothing, but with Leibnitz it has a very important part to play. According to him, in every monad, every other is reflected; every monad is a living mirror of the universe, and ideally contains the whole within itself as in a germ. In thus mirroring the world, however, the monad is not passive but spontaneously self-active: it does not receive the images which it mirrors, but produces them spontaneously itself, as the soul does a dream. In every monad, therefore, the all-seeing and all-knowing one might read every thing, even the future, since this is potentially contained in the present. Every monad is a kind of God. (Parvus in suo genere Deus.)

3. The Pre-established Harmony.—The universe is thus the sum of all the monads. Every thing, every composite, is an aggregate of monads. Thus every bodily organism is not one substance, but many, it is a multiplicity of monads, like a machine which is made up of a number of distinct pieces of mechanism. Leibnitz compared bodies to a fish-pond, which might be full of living elements, though dead itself. The ordinary view of things is thus wholly set aside; the truly substantial does not belong to bodies, i. e. to the aggregates, but to their original elements. Matter, in the vulgar sense, as something conceived to be without mind, does not at all exist. How now must the inner connection of the universe be conceived? In the following way. Every monad is a representative being, and at the same time, each one is different from every other. This difference, therefore, depends alone upon the difference of representation: there are just as many different degrees of representation as there are monads, and these degrees may be fixed according to some of their prominent stages. The representations may be classified according to the distinction between confused and distinct knowledge. Hence a monad of the lowest rank (a monad toute nue) will be one which simply represents, i. e. which stands on the stage of most confused knowledge. Leibnitz compares this state with a swoon, or with our condition in a dreamy sleep, in which we are not without representations, (notions)—for otherwise we could have none when awaking—but in which the representations are so numerous that they neutralize each other and do not come into the consciousness. This is the stage of inorganic nature. In a higher rank are those monads in which the representation is active as a formative vital force, though still without consciousness. This is the stage of the vegetable world. Still higher ascends the life of the monad when it attains to sensation and memory, as is the case in the animal kingdom. The lower monads may be said to sleep, and the brute monads to dream. When still farther the soul rises to reason or reflection, we call it mind, spirit.—The distinction of the monads from each other is, therefore, this, that each one, though mirroring the whole and the same universe in itself, does it from a different point of view, and, therefore, differently, the one more, and the rest less perfectly. Each one is a different centre of the world which it mirrors. Each one contains the whole universe, the whole infinity within itself, and in this respect is like God, the only difference being that God knows every thing with perfect distinctness, while the monad represents it confusedly, though one monad may represent it more confusedly than another. The limitation of a monad does not, therefore, consist in its containing less than another or than God, but only in its containing more imperfectly or in its representing less distinctly.—Upon this standpoint the universe, in so far as every monad mirrors one and the same universe, though each in a different way, represents a drama of the greatest possible difference, as well as of the greatest possible unity and order, i. e. of the greatest possible perfection, or the absolute harmony. For distinction in unity is harmony.—But in still another respect the universe is a system of harmony. Since the monads do not work upon each other, but each one follows only the law of its own being, there is danger lest the inner harmony of the universe may be disturbed. How is this danger removed? Thus, viz., every monad mirrors the whole and the same universe. The changes of the collected monads, therefore, run parallel with each other, and in this consists the harmony of all as pre-established by God.

4. The Relation of the Deity to the Monads.—What part does the conception of God play in the system of Leibnitz? An almost idle one. Following the strict consequences of his system, Leibnitz should have held to no proper theism, but the harmony of the universe should have taken the place of the Deity. Ordinarily he considers God as the sufficient cause of all monads. But he was also accustomed to consider the final cause of a thing as its sufficient cause. In this respect, therefore, he almost identifies God and the absolute final cause. Elsewhere he considers the Deity as a simple primitive substance, or as the individual primitive unity. Again, he speaks of God as a pure immaterial actuality, actus purus, while to the monads belongs matter, i. e. restrained actuality, striving, appetitio. Once he calls him a monad, though this is in manifest contradiction with the determinations otherwise assigned him. It was for Leibnitz a very difficult problem to bring his monadology and his theism into harmony with each other, without giving up the premises of both. If he held fast to the substantiality of the monads, he was in danger of making them independent of the Deity, and if he did not, he could hardly escape falling back into Spinozism.

5. The Relation of Soul and Body is clearly explained on the standpoint of the pre-established harmony. This relation, taking the premises of the monadology, might seem enigmatical. If no monad can work upon any other, how can the soul work upon the body to lead and move it? The enigma is solved by the pre-established harmony. While the body and soul, each one independently of the other, follows the laws of its being, the body working mechanically, and the soul pursuing ends, yet God has established such a concordant harmony of the two activities, such a parallelism of the two functions, that there is in fact a perfect unity for body and soul. There are, says Leibnitz, three views respecting the relation of body and soul. The first and most common supposes a reciprocal influence between the two, but such a view is untenable, because there can be no interchange between mind and matter. The second and occasional one (cf. § XXV. 1), brings about this interchange through the constant assistance of God, which is nothing more nor less than to make God a Deus ex machina. Hence the only solution for the problem is the hypothesis of a pre-established harmony. Leibnitz illustrates these three views in the following example. Let one conceive of two watches, whose hands ever accurately point to the same time. This agreement may be explained, first (the common view), by supposing an actual connection between the hands of each, so that the hand of the one watch might draw the hand of the other after it, or second (the occasional view), by conceiving of a watch-maker who continually keeps the hands alike, or in fine (the pre-established harmony), by ascribing to each a mechanism so exquisitely wrought that each one goes in perfect independence of the other, and at the same time in entire agreement with it.—That the soul is immortal (indestructible), follows at once from the doctrine of monads. There is no proper death. That which is called death is only the soul losing a part of the monads which compose the mechanism of its body, while the living element goes back to a condition similar to that in which it was before it came upon the theatre of the world.

6. The monadology has very important consequences in reference to THE THEORY OF KNOWLEDGE. As the philosophy of Leibnitz, by its opposition to Spinozism, had to do with the doctrine of being, so by its opposition to the empiricism of Locke must it expound the theory of knowledge. Locke’s Essay on the Human Understanding had attracted Leibnitz without satisfying him, and he therefore attempted a new investigation in his Nouveaux Essais, in which he defended the doctrine of innate ideas. But this hypothesis of innate ideas Leibnitz now freed from that defective view which had justified the objections of Locke. The innateness of the ideas must not be held as though they were explicitly and consciously contained in the mind, but rather the mind possesses them potentially and only virtually, though with the capacity to produce them out of itself. All thoughts are properly innate, i. e. they do not come into the mind from without, but are rather produced by it from itself. Any external influence upon the mind is inconceivable, it even needs nothing external for its sensations. While Locke had compared the mind to an unwritten piece of paper, Leibnitz likened it to a block of marble, in which the veins prefigure the form of the statue. Hence the common antithesis between rational and empirical knowledge disappears with Leibnitz in the degrees of greater or less distinctness.—Among these theoretically innate ideas, Leibnitz recognizes two of special prominence, which take the first rank as principles of all knowledge and all ratiocination,—the principle of contradiction (principium contradictionis), and the principle of sufficient cause (principium rationis sufficientis). To these, as a principle of the second rank, must be added the principium indiscernibilium, or the principle that there are in nature no two things wholly alike.

7. The most elaborate exhibition of Leibnitz’s theological views is given in his ThÉodicÉe. The ThÉodicÉe, is, however, his weakest work, and has but a loose connection with the rest of his philosophy. Written at the instigation of a woman, it belies this origin neither in its form nor in its content—not in its form, for in its effort to be popular it becomes diffuse and unscientific, and not in its content, for it accommodates itself to the positive dogmas and the premises of theology farther than the scientific basis of the system of Leibnitz would permit. In this work, Leibnitz investigates the relation of God to the world in order to show a conformity in this relation to a final cause, and to free God from the charge of acting without or contrary to an aim. Why is the world as it is? God might have created it very differently. True, answers Leibnitz, God saw an infinite number of worlds as possible before him, but out of all these he chose the one which actually is as the best. This is the famous doctrine of the best world, according to which no more perfect world is possible than the one which is.—But how so? Is not the existence of evil at variance with this? Leibnitz answers this objection by distinguishing three kinds of evil, the metaphysical, the physical, and the moral. The metaphysical evil, i. e. the finiteness and incompleteness of things, is necessary because inseparable from finite existence, and is thus independent of the will of God. Physical evil (pain, &c.), though not independent of the will of God, is often a good conditionally, i. e. as a punishment or means of improvement. Moral evil or wickedness can in no way be charged to the will of God. Leibnitz took various ways to account for its existence, and obviate the contradiction lying between it and the conception of God. At one time he says that wickedness is only permitted by God as a conditio sine qua non, because without wickedness there were no freedom, and without freedom no virtue. Again, he reduces the moral evil to the metaphysical, and makes wickedness nothing but a want of perfection, a negation, a limitation, playing the same part as do the shadows in a painted picture, or the discords in a piece of music, which do not diminish the beauty, but only increase it through contrast. Again, he distinguishes between the material and the formal element in a wicked act. The material of sin, the power to act, is from God, but the formal element, the wickedness of the act, belongs wholly to man, and is the result of his limitation, or, as Leibnitz here and there expresses it, of his eternal self-predestination. In no case can the harmony of the universe be destroyed through such a cause.

These are the chief points of Leibnitz’s philosophy. The general characteristic of it as given in the beginning of the present section, will be found to have its sanction in the specific exhibition that has now been furnished.