In conformity with this more inclusive meaning, perception is defined as the representation of the external in the internal, of multiplicity in unity (representatio multitudinis in unitate). The representing being, without prejudice to its simplicity, bears in itself a multitude of relations to external things. What now is the manifold, which is expressed, perceived, or represented, in the unit, the monad? It is the whole world. Every monad represents all others in itself, is a concentrated all, the universe in miniature. Each individual contains an infinity in itself (substantia infinitas actiones simul exercet) and a supreme intelligence, for which every obscure idea would at once become distinct, would be able to read in a single monad the whole universe and its history—all that is, has been, or will be; for the past has left its traces behind it, and the future will bring nothing not founded in the present: the monad is freighted with the past and bears the future in its bosom. Every monad is thus a mirror of the universe,[1] but a living mirror (miror vivant de l'univers), which generates the images of things by its own activity or develops them from inner germs, without experiencing influences from without. The monad has no windows through which anything could pass in or out, but in its action is dependent only on God and on itself.
[Footnote 1: The objection has been made against Leibnitz, and not without reason, that strictly speaking there is no content for the representation of the monads, although he appears to offer them the richest of all contents, the whole world. The "All" which he makes them represent is itself nothing but a sum of beings, also representative. The objects of representation are merely representing subjects; the monad A represents the monads from B to Z, while these in turn do nothing more than represent one another. The monad mirrors mirrors—where is the thing that is mirrored? The essence of substance consists in being related to others, which themselves are only points of relation; amid mere relativities we never reach a real. That which prevented Leibnitz himself from recognizing this empty formalism was, no doubt, the fact that for him the mere form of representation was at once filled with a manifold experiential content, with the whole wealth of spiritual life, and that the quantitative differences in representation, which for him meant also degrees of feeling, desire, action, and progress, imperceptibly took on the qualitative vividness of individual characteristics. Moreover, it must not be overlooked that the spiritual beings represent not merely the universe but the Deity as well, hence a very rich object.]
All monads represent the same universe, but each one represents it differently, that is, from its particular point of view—represents that which is near at hand distinctly, and that which is distant confusedly. Since they all reflect the same content or object, their difference consists only in the energy or degree of clearness in their representations. So far then, as their action consists in representation, distinct representation evidently coincides with complete, unhindered activity, confused representation with arrested activity, or passivity. The clearer the representations of a monad the more active it is. To have clear and distinct perceptions only is the prerogative of God; to the Omnipresent everything is alike near. He alone is pure activity; all finite beings are passive as well, that is, so far as their perceptions are not clear and distinct. Retaining the Aristotelian-Scholastic terminology, Leibnitz calls the active principle form, the passive matter, and makes the monad, since it is not, like God, purus actus and pure form, consist of form (entelechy, soul) and matter. This matter, as a constituent of the monad, does not mean corporeality, but only the ground for the arrest of its activity. The materia prima (the principle of passivity in the monad) is the ground, the materia secunda (the phenomenon of corporeal mass) the result of the indistinctness of the representations. For a group of monads appears as a body when it is indistinctly perceived. Whoever deprives the monad of activity falls into the error of Spinoza; whoever takes away its passivity or matter falls into the opposite error, for he deifies individual beings.
No monad represents the common universe and its individual parts just as well as the others, but either better or worse. There are as many different degrees of clearness and distinctness as there are monads.
Nevertheless certain classes may be distinguished. By distinguishing between clear and obscure perceptions, and in the former class between distinct and confused ones—a perception is clear when it is sufficiently distinguished from others, distinct when its component parts are thus distinguished—Leibnitz reaches three principal grades. Lowest stand the simple or naked monads, which never rise above obscure and unconscious perception and, so to speak, pass their lives in a swoon or sleep. If perception rises into conscious feeling, accompanied by memory, then the monad deserves the name of soul. And if the soul rises to self-consciousness and to reason or the knowledge of universal truth, it is called spirit. Each higher stage comprehends the lower, since even in spirits many perceptions remain obscure and confused. Hence it was an error when the Cartesians made thought or conscious activity—by which, it is true, the spirit is differentiated from the lower beings—to such a degree the essence of spirit that they believed it necessary to deny to it all unconscious perceptions.
From perception arises appetition, not as independent activity, but as a modification of perception; it is nothing but the tendency to pass from one perception to another (l'appetit est la tendance d'une perception à une autre); impulse is perception in process of becoming. Where the perceptions are conscious and rational appetition rises into will. All monads are self-active or act spontaneously, but only the thinking ones are free. Freedom is the spontaneity of spirits. Freedom does not consist in undetermined choice, but in action without external compulsion according to the laws of one's own being. The monad develops its representations out of itself, from the germs which form its nature. The correspondence of the different pictures of the world, however, is grounded in a divine arrangement, through which the natures of the monads have from the beginning been so adapted to one another that the changes in their states, although they take place in each according to immanent laws and without external influence, follow an exactly parallel course, and the result is the same as though there were a constant mutual interaction. This general idea of a pre-established harmony finds special application in the problem of the interaction between body and soul. Body and soul are like two clocks so excellently constructed that, without needing to be regulated by each other, they show exactly the same time. Over the numberless lesser miracles with which occasionalism burdened the Deity, the one great miracle of the pre-established harmony has an undeniable advantage. As one great miracle it is more worthy of the divine wisdom than the many lesser ones, nay, it is really no miracle at all, since the harmony does not interfere with natural laws, but yields them. This idea may even be freed from its theological investiture and reduced to the purely metaphysical expression, that the natures of the monads, by which the succession of their representations is determined in conformity with law, consist in nothing else than the sum of relations in which this individual thing stands to all other parts of the world, wherein each member takes account of all others and at the same time is considered by them, and thus exerts influence as well as suffers it. In this way the external idea of an artificial adaptation is avoided. The essence of each thing is simply the position which it occupies in the organic whole of the universe; each member is related to every other and shares actively and passively in the life of all the rest. The history of the universe is a single great process in numberless reflections.
The metaphysics of Leibnitz begins with the concept of representation and ends with the harmony of the universe. The representations were multiplicity (the endless plurality of the represented) in unity (the unity of the representing monad); the harmony is unity (order, congruity of the world-image) in multiplicity (the infinitely manifold degrees of clearness in the representations). All monads represent the same universe; each one mirrors it differently. The unity, as well as the difference, could not be greater than it is; every possible degree of distinctness of representation is present in each single monad, and yet there is a single harmonic accord in which the unnumbered tones unite. Now order amid diversity, unity in variety make up the concept of beauty and perfection. If, then, this world shows, as it does, the greatest unity in the greatest multiplicity, so that there is nothing wanting and nothing superfluous, it is the most perfect, the best of all possible worlds. Even the lowest grades contribute to the perfection of the whole; their disappearance would mean a hiatus; and if the unclear and confused representations appear imperfect when considered in themselves, yet they are not so in reference to the whole; for just on this fact, that the monad is arrested in its representation or is passive, i.e., conforms itself to the others and subordinates itself to them, rest the order and connection of the world. Thus the idea of harmony forms the bridge between the Monadology and optimism.
As in regard to the harmony of the universe we found it possible to distinguish between a half-mythical, narrative form of presentation and a purely abstract conception, so we may make a similar distinction in the doctrine of creation. This actual world has been chosen by God as the best among many other conceivable worlds. Through the will of God the monads of which the world consists attained their reality; as possibilities or ideas they were present in the mind of God (as it were, prior to their actualization), present, too, with all the distinctive properties and perfections that they now exhibit in a state of realization, so that their merely possible or conceivable being had the same content as their actual being, and their essence is not altered or increased by their existence. Now, since the impulse toward actualization dwells in every possible essence, and is the more justifiable the more perfect the essence, a competition goes on before God, in which, first, those monod-possibilities unite which are mutually compatible or compossible, and, then, among the different conceivable combinations of monads or worlds that one is ordained for entrance into existence which shows the greatest possible sum of perfection. It was, therefore, not the perfection of the single monad, but the perfection of the system of which it forms a necessary part, that was decisive as to its admission into existence. The best world was known through God's wisdom, chosen through his goodness, and realized through his power.[1] The choice was by no means arbitrary, but wholly determined by the law of fitness or of the best (principe du meilleur); God's will must realize that which his understanding recognizes as most perfect. It is at once evident that in the competition of the possible worlds the victory of the best was assured by the lex melioris, apart from the divine decision.
[Footnote 1: In regard to the dependence of the world on God, there is a certain conflict noticeable in Leibnitz between the metaphysical interests involved in the substantiality of individual beings, together with the moral interests involved in guarding against fatalism, and the opposing interests of religion. On the one side, creation is for him only an actualization of finished, unchangeable possibilities, on the other, he teaches with the mediaeval philosophers that this was not accomplished by a single act of realization, that the world has need of conservation, i.e., of continuous creation.]
This law is the special expression of a more general one, the principle of sufficient reason, which Leibnitz added, as of equal authority, to the Aristotelian laws of thought. Things or events are real (and assertions true) when there is a sufficient reason for their existence, and for their determinate existence. The principium rationis sufficientis governs our empirical knowledge of contingent truths or truths of fact, while, on the other hand, the pure rational knowledge of necessary or eternal (mathematical and metaphysical) truths rests on the principium contradictionis. The principle of contradiction asserts, that is, whatever contains a contradiction is false or impossible; whatever contains no contradiction is possible; that whose opposite contains a contradiction is necessary. Or positively formulated as the principle of identity, everything and every representative content is identical with itself.[2] Upon this antithesis between the rational laws of contradiction and sufficient reason—which, however, is such only for us men, while the divine spirit, which cognizes all things a priori, is able to reduce even the truths of fact to the eternal truths—Leibnitz bases his distinction between two kinds of necessity. That is metaphysically necessary whose opposite involves a contradiction; that is morally necessary or contingent which, on account of its fitness, is preferred by God to its (equally conceivable) opposite. To the latter class belongs, further, the physically necessary: the necessity of the laws of nature is only a conditional necessity (conditioned by the choice of the best); they are contingent truths or truths of fact. The principle of sufficient reason holds for efficient as well as for final causes, and between the two realms there is, according to Leibnitz, the most complete correspondence. In the material world every particular must be explained in a purely mechanical way, but the totality of the laws of nature, the universal mechanism itself, cannot in turn be mechanically explained, but only on the basis of finality, so that the mechanical point of view is comprehended in, and subordinated to, the teleological. Thus it becomes clear how Leibnitz in the ratio sufficiens has final causes chiefly in mind.