Discourse on Metaphysics and the Monadology. Gottfried Leibniz
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whenever they can.
It is therefore wrong to say that the Cartesian line of thought has completely failed and that modern science has been moving away from it more and more. On the contrary we are witnessing the daily extension of mechanicalism in the science of our time. The question takes on a different phase when it is asked whether mechanicalism is the final word of nature, whether it is self-sufficient, in fact whether the principles of mechanicalism are themselves mechanical. This is a wholly metaphysical question and does not at all affect positive science; for the phenomena will be explained in the same way whether matter is thought of as inert, composed of little particles which are moved and combined by invisible hands, or whether an interior activity and a sort of spontaneity is attributed to them. For the physicist and for the chemist, forces are only words representing unknown causes. For the metaphysician they are real activities. It is metaphysics, therefore, and not physics which is rising above mechanicalism. It is in metaphysics that mechanicalism has found, not its contradiction, but its completion through the doctrine of dynamism. It is this latter direction that philosophy has mainly taken since Descartes and in this the prime mover was Leibniz.{2}
In order to understand Leibniz’s system we must not forget a point to which sufficient attention has not been paid, namely, that Leibniz never gave up or rejected the mechanicalism of Descartes. He always affirmed that everything in nature could be explained mechanically; that, in the explanation of phenomena, recourse must never be had to occult causes; so far indeed did he press this position that he refused to admit Newton’s attraction of gravitation, suspecting it of being an occult quality: while, however, Leibniz admitted with Descartes the application of mechanicalism he differed from him in regard to the basis of it and he is continually repeating that if everything in nature is mechanical, geometrical and mathematical the source of mechanicalism is in metaphysics.{3}
Descartes explained everything geometrically and mechanically, that is by extension, form, and motion, just as Democritus had done before; but he did not go farther, finding in extension the very essence of corporeal substance. Leibniz’s genius showed itself when he pointed out that extension does not suffice to explain phenomena and that it has need itself of an explanation. Brought up in the scholastic and peripatetic philosophy, he was naturally predisposed to accord more of reality to the corporeal substance, and his own reflections soon carried him much farther along the same line.
It is also worth noticing, as Guhrauer has said in his Life of Leibniz, that it was a theological problem which put Leibniz upon the track of reforming the conception of substance. The question was rife as to the real presence in transubstantiation. This problem seemed inexplicable upon the Cartesian hypothesis, for if the essence of a body is its extension, it is a contradiction that the same body can be found in several places at the same time. Leibniz, writing to Arnauld in 1671, says he thinks he has found the solution to this great problem since he has discovered “that the essence of a body does not consist in extension, that the corporeal substance, even taken by itself, is not extension and is not subject to the conditions of extension. This would have been evident if the real character of substance had been discovered sooner.”
Leaving aside this point, however, the following are the different considerations which led Leibniz to admit non-mechanical principles as above corporeal mechanicalism, and to reduce the idea of the body to the idea of active indivisible substances, entelechies or monads, having innate within themselves the reason for all their determinations.
1. The first and principal reason which Leibniz brings up against Descartes is that, “If all that there is in bodies is extension and the position of the parts, then when two bodies come into contact and move on together after the contact, that one which was in motion will carry along the body at rest without losing any of its velocity, and the difference in the sizes of the bodies will effect no change,” which is contrary to experience. A body in motion which comes in contact with one at rest loses some of its velocity and its direction is modified, which would not happen if the body were purely passive. “Higher conceptions must therefore be added to extension, namely, the conceptions of substance, action and force; these latter carry the idea that that which suffers action, acts reciprocally and that that which acts is reacted upon.”{4}
2. Extension cannot serve to give the reason for the changes which take place in bodies, for extension with its various modifications constitutes what is called in the school terminology extrinsic characteristics, whence nothing can result for the being itself; whether a body be round or square does not affect its interior condition, nor can any particular change result for it.{5} Furthermore, every philosophy which is exclusively mechanical is obliged to deny change and to hold that everything is changeless and that there are only modifications of position or displacements in space or motion. Who does not see, however, that motion itself is a change, and should have its reason in the being which moves or which is moved, for even passive motion must correspond to something in the essence of the body moved? Besides if corporeal elements differ from one another through form, why have they one form rather than any other? Epicurus talks to us of round and hooked atoms. Why is a certain atom round and another hooked? Should not the reason be in the very substance of the atom? Therefore form, position, motion and all the extrinsic modifications of bodies should emanate from an internal principle analogous to that which Aristotle calls nature or entelechy.{6}
3. Extension cannot be substance. On the contrary it presupposes substance. “Aside from extension there must be a subject which is extended, that is, a substance to which continuity appertains. For extension signifies only a continued repetition or multiplication of that which is expanded, a plurality, a continuity or co-existence of parts and consequently it does not suffice to explain the real nature of expanded or repeated substance whose conception precedes that of repetition.”{7}
4. Another reason given by Leibniz is that the conception of substance necessarily implies the idea of unity. No one thinks that two stones very far apart form a single substance. If now we imagine them joined and soldered together, will this juxtaposition change the nature of things? Of course not; there will always be two stones and not a single one. If now we imagine them attached by an irresistible force, the impossibility of separating them will not prevent the mind from distinguishing them and will not prevent their remaining two and not one. In a word every compound is no more a single substance than is a pile of sand or a sack of wheat. We might as well say that the employees of the India Company formed a single substance.{8} It is evident therefore that a compound is never a substance and in order to find the real substance we must attain unity or the indivisible. To say that there are no such unities is to say that matter has no elements, in other words that it is not made up of substance but it is a pure phenomenon like the rainbow. The conclusion is then either that matter has no substantial reality or else it must be admitted that it is reducible to simple and consequently unextended elements, called monads.
5. Leibniz brings forward another argument in behalf of his theory of monads. This is that the essence of every substance is in force, which fact is as true of the soul as of the body. It can be proved a priori. Is it not evident that a being really exists only in so far as it acts? A being absolutely passive would be a pure nothing, and would involve a contradiction; or, by hypothesis, receiving everything from outside and having nothing through itself, it would have no characteristic, no attribute and hence would be a pure nothing. The mere fact of existence, therefore, already supposes a certain force and a certain energy.
Leibniz presses this thought of the activity of substances so far that he even admits no degree of passivity. According to him, no substance is, properly speaking, passive. Passion in a substance is nothing else than an action considered bound to another action in another substance. Every substance acts only through itself and cannot act upon any other. The monads have no windows through which to receive anything from outside. They do not undergo any action and consequently are never passive. All that takes place in them is the spontaneous development of their own essence. All that there is, is that the states of each one correspond to the states of all the others. When we consider one of these states in one monad as corresponding to a certain other state in another monad, in such a way that the latter is the condition of the former, the first state is called a passion and the second an action. There is, therefore, between all monad-substances a pre-established harmony, in accordance with which each one represents (or expresses, as Leibniz says) the whole universe.