When he was in Vienna in 1714 he met Eugene of Savoy, who, with Marlborough, had saved Europe from subjection to Louis XIV. The Prince asked the philosopher for a brief statement of his philosophy in a form intelligible to a general. Leibniz responded by composing a compact treatise of ninety paragraphs, which he left among his papers at his death. A German translation was published in 1720, but the original French text was not printed till 1839, and then it was the editor who christened it La Monadologie. Leibniz could have taken the term monad from Giordano Bruno, 49 or from Frans (son of the chemist J. B.) van Helmont, 50 who used the word to describe the minute “seeds” which alone were directly created by God, and which developed into all the forms of matter and life. An English physician, Francis Glisson, had attributed not only force but instinct and ideas to all substances (1672). A similar theory had germinated in Leibniz’ roving and receptive mind since 1686. He may have been influenced by the recent work of microscopists, who had shown such throbbing life in the smallest cells. Leibniz concluded that “there is a world of created beings—living things, animals . . . , souls . . . , in the least part of matter.” 51 Every portion of matter may be conceived as a pond full of fishes, and every drop of blood in one of these microscopic fishes is another pond full of fishes, and so on ad infinitum. He was moved—as Pascal had been appalled—by the indefinite divisibility of every extended thing.
This endless divisibility, Leibniz suggested, is a puzzle arising from our conception of reality as matter, therefore as extended, therefore as divisible ad nauseam. If we consider the ultimate reality as energy, and conceive the world as composed of centers of force, the mystery of divisibility vanishes, because force, like thought, does not imply extension. So he rejected the atoms of Democritus as the ultimate components of the universe, and replaced them with monads, unextended units of force; he defined substance not as matter but as energy. (Up to this point Leibniz’ conception was quite in accord with twentieth-century physics.) “Matter” is everywhere instinct with motion, activity, and life. Every monad feels or perceives; it has inchoate or incipient mind, in the sense that it is susceptible—and responds—to external changes.
We shall understand the monads better if we think of them “in imitation of the notion that we have of souls.” 52 As each soul is “a simple, separate Person,” 53 a solitary ego, solus contra mundum, fighting its way by its own internal will against everything outside it, so each monad is essentially alone, a separate, independent center of force against all other centers of force; reality is a universe of individual powers, unified and harmonized only through the laws of the whole, or God. As every soul is different from all others, so is every monad unique; in the entire cosmos there are no two beings completely alike, for their differences constitute their individuality; two things having all the same qualities would be indistinguishable, identical, one (“the law of indiscernibles”). 54As each soul feels or perceives the reality surrounding it, and, ever less clearly, the reality progressively distant from it, but feels all reality in some degree, so each monad feels, however confusedly and unconsciously, the whole universe; in this way it is a mirror more or less obscurely reflecting and representing the world. And as no individual mind can really look into another mind, so no single monad can see into another; it has no window or other opening for such direct communication; and therefore it cannot directly produce any change in any other monad.
The monads do change, for change is essential to their life; but the changes come from their own inner striving. 55 For just as each self is desire and will, so each monad contains—is—an inner purpose and will, an effort to develop; this is the “entelechy” that Aristotle spoke of as the core of every life; in this sense [as Schopenhauer was to say] force and will are two forms or degrees of the same fundamental reality. 56 There is an immanent teleology in nature: there is in everything a seeking, an “appetition,” a guiding, molding purpose, even though that purpose, that will, acts within the limits, and by means, of mechanical law. Just as, in ourselves, the bodily movement is the visible and mechanical expression of an internal will or desire, so in the monads the mechanical process that we see from without is only the outer form and shell of an inner force: “That which is exhibited mechanically, or by extension, in matter, is concentrated dynamically and monadically in the entelechy [or inner striving] itself.” 57 In our confused perception we identify external things with “matter” because we see their outer mechanism only; we do not, as in introspection, see the inner and formative vitality. In this philosophy the passive and helpless atoms of the materialists give place to monads, or units, that are living centers of individuality and force; the world ceases to be a dead machine, and becomes the stage of diverse and palpitating life.
In that diversity the most important feature is the degree in which the “mind” of the monad is conscious. All monads have mind, in the sense of sensitivity and response; but not all mind is conscious. Even we marvelous human beings go through many mental processes without consciousness, as in dreams; or as when, in our intense attention to certain aspects of a situation, we are not aware that we are perceiving many other elements in the scene—elements which may nevertheless be deposited in memory, enter into our dreams, or emerge from hidden corners of the mind into later consciousness; or as when, conscious of the roar and hiss of the surf, we do not realize that each wave, and each particle of each wave, is beating upon our ears to produce a thousand individual impressions that become our hearing of the sea. So the simplest monads feel and perceive everything about them, but so confusedly that they have no consciousness. In plants the feelings become clearer and more specialized, and lead to more specific responses. In the monad that is the soul of an animal the echoing perceptions become memories, whose interplay begets consciousness. Man is a colony of monads [cells?], each with its own hunger, needs, and purposes; but these particles become a unified community of living organisms under the direction of a dominating monad which is man’s entelechy and soul. 58 “When this soul is raised to the level of reason, it is . . . reckoned as mind,” 59 and rises in rank in the measure of its perceiving necessary relations and eternal truths; when it perceives the order and mind of the universe it becomes the mirror of God. God, the Prime Monad, is pure and fully conscious Mind, free from mechanism and body. 60
The most difficult aspect of this philosophy is Leibniz’ theory of “preestablished harmony.” What is the relation between the inner life of a monad and its outward manifestation, or material shell? And how shall we explain the apparent interaction of physical body and spiritual mind in man? Descartes had delegated this problem helplessly to the pineal gland; Spinoza had answered it by denying any separation or interaction of matter and mind, since these were, in his view, merely the outside and inside aspects of one process and reality. Leibniz restored the problem by thinking of the two aspects as separate and distinct; he denied their interaction, but ascribed the simultaneity of the physical and the mental processes as due to a continuous collusion marvelously prearranged by God:
The soul follows its own laws, and the body its own likewise, and they accord by virtue of the harmony pre-established among all substances, since they are all representations of one and the same universe. 61 . . . Bodies act as though, per impossibile, there were no souls, and souls act as if there were no bodies, and both act as if each influenced the other. 62 . . . I am . . . asked how it happens that God is not content to produce all the thoughts and modifications of the soul without these useless bodies which the soul (it is said) can neither move nor know. The answer is easy. It is that it was God’s will that there should be a greater rather than a lesser number of substances, and He found it good that these modifications should correspond to something outside. 63
Suspecting that this debonair exploitation of deity as a substitute for thought might not win universal applause, Leibniz embellished it with the occasionalism and timepieces of Geulincx: body and mind, each operating independently of the other and yet in puzzling harmony, are like two clocks so skillfully constructed, wound, and set that they tick off the seconds and strike the hours in perfect agreement, without any interaction or mutual influence; so the physical and psychical processes, though quite independent, and never acting upon each other, accord through a “harmony pre-established by a divine anticipatory artifice.” 64
Let us assume that what Leibniz had in view, but did not care to say, was that the apparently separate but synchronous processes of mechanism and life, of action and thought, are one and the same process, seen externally as matter, internally as mind. But to have said this would have been to repeat Spinoza, and share his fate.