Leibniz's New Essays Concerning the Human Understanding Part 4

CHAPTER VII.

MATTER AND ITS RELATION TO SPIRIT.

Locke's account of innate ideas and of sensation is only preparatory to a discussion of the ideas got by sensation. His explanation of the mode of knowledge leads up to an explanation of the things known. He remains true to his fundamental idea that before we come to conclusions about any matters we must "examine our own ability." He deals first with ideas got by the senses, whether by some one or by their conjoint action. Of these the ideas of solidity, of extension, and of duration are of most concern to us. They form as near an approach to a general philosophy of nature as may be found anywhere in Locke. They are, too, the germ from which grew the ideas of matter, of s.p.a.ce, and of time, which, however more comprehensive in scope and more amply worked out in detail, characterize succeeding British thought, and which are reproduced to-day by Mr. Spencer.

"The idea of solidity we receive by our touch." "The ideas we get by more than one sense are of s.p.a.ce or extension, figure, rest, and motion." These sentences contain the brief statement of the chief contention of the sensational school. Locke certainly was not conscious when he wrote them that they were the expression of ideas which should resolve the world of matter and of s.p.a.ce into a dissolving series of accidentally a.s.sociated sensations; but such was none the less the case. When he writes, "If any one asks me what solidity is, I send him to his senses to inform him," he is preparing the way for Berkeley, and for a denial of all reality beyond the feelings of the individual mind. When he says that "we get the idea of s.p.a.ce both by sight and touch," this statement, although appearing truistic, is none the less the source of the contention of Hume that even geometry contains no necessary or universal elements, but is an account of sensible appearances, relative, as are all matters of sensation.

Locke's ideas may be synopsized as follows: It is a sufficient account of solidity to say that it is got by touch and that it arises from the resistance found in bodies to the entrance of any other body. "It is that which hinders the approach of two bodies when they are moved towards one another." If not identical with matter, it is at all events its most essential property. "This of all others seems the idea most intimately connected with and essential to body, so as nowhere else to be found or imagined, but only in matter." It is, moreover, the source of the other properties of matter. "Upon the solidity of bodies depend their mutual impulse, resistance, and protrusion." Solidity, again, "is so inseparable an idea from body that upon that depends its filling of s.p.a.ce, its contact, impulse, and communication of motion upon impulse." It is to be distinguished, therefore, from hardness, for hardness is relative and derived, various bodies having various degrees of it; while solidity consists in utter exclusion of other bodies from the s.p.a.ce possessed by any one, so that the hardest body has no more solidity than the softest.

The close connection between solidity and matter makes it not only possible, but necessary, to distinguish between matter and extension as against the Cartesians, who had identified them. In particular Locke notes three differences between these notions. Extension includes neither solidity nor resistance; its parts are inseparable from one another both really and mentally, and are immovable; while matter has solidity, its parts are mutually separable, and may be moved _in_ s.p.a.ce. From this distinction between s.p.a.ce and matter it follows, according to Locke, that there is such a thing as a vacuum, or that s.p.a.ce is not necessarily a plenum of matter. Matter is that which fills s.p.a.ce; but it is entirely indifferent to s.p.a.ce whether or not it is filled. s.p.a.ce is occupied by matter, but there is no essential relation between them. Solidity is the essence of matter; emptiness is the characteristic of s.p.a.ce. "The idea of s.p.a.ce is as distinct from that of solidity as it is from that of scarlet color. It is true, solidity cannot exist without extension, neither can scarlet color exist without extension; but this hinders not that they are _distinct ideas_."

Thus there is fixed for us the idea of s.p.a.ce as well as of matter. It is a distinct idea; that is, absolute or independent in itself, having no intrinsic connection with phenomena _in_ s.p.a.ce. Yet it is got through the senses. How that can be a matter of sensation which is not only not material, but has no connection in itself with matter, Locke does not explain. He thinks it sufficient to say that we see distance between bodies of different color just as plainly as we see the colors. s.p.a.ce is, therefore, a purely immediate idea, containing no more organic relation to intelligence than it has to objects. We get the notion of time as we do that of s.p.a.ce, excepting that it is the observation of internal states and not of external objects which furnishes the material of the idea. Time has two elements,--succession and duration. "Observing what pa.s.ses in the mind, how of our ideas there in train some constantly vanish, and others begin to appear, we come by the idea of succession, and by observing a distance in the parts of this succession we get the idea of duration." Whether, however, time is something essentially empty, having no relation to the events which fill it, as s.p.a.ce is essentially empty, without necessary connection with the objects which fill it, is a question Locke does not consider. In fact, the gist of his ideas upon this point is as follows: there is actually an objective s.p.a.ce or pure emptiness; employing our senses, we get the idea of this s.p.a.ce. There is actually an objective time; employing reflection, we perceive it. There is not the slightest attempt to form a philosophy of them, or to show their function in the construction of an intelligible world, except in the one point of the absolute independence of matter and s.p.a.ce.

It cannot be said that Leibniz criticises the minor points of Locke in such a way as to throw much light upon them, or that he very fully expresses his own ideas about them. He contents himself with declaring that while the senses may give instances of s.p.a.ce, time, and matter, and may suggest to intelligence the stimuli upon which intelligence realizes these notions from itself, they cannot be the source of these notions themselves; finding the evidence of this in the sciences of geometry, arithmetic, and pure physics. For these sciences deal with the notions of s.p.a.ce, time, and matter, giving necessary and demonstrative ideas concerning them, which the senses can never legitimate. He further denies the supposed absoluteness or independence of s.p.a.ce, matter, and motion. Admitting, indeed, the distinction between extension and matter, he denies that this distinction suffices to prove the existence, or even the possibility, of a vacuum, and ends with a general reference to his doctrine of pre-established harmony, as serving to explain these matters more fully and more accurately.

Leibniz has, however, a complete philosophy of nature. In his other writing, he explains the ideas of matter and force in their dependence upon his metaphysic, or doctrine of spiritual entelechies. The task does not at first sight appear an easy one. The reality, according to Leibniz, is purely spiritual, does not exist in s.p.a.ce nor time, and is a principle of activity following its own law,--that of reflecting the universe of spiritual relations. How from this world of ideal, unextended, and non-temporal dynamic realities we are to pa.s.s over to a material world of extension, with its static existence in s.p.a.ce, and transitory pa.s.sage in time, is a question challenging the whole Leibnizian system. It is a question, however, for which Leibniz himself has provided an answer. We may not regard it as adequate; we may think that he has not truly derived the material world from his spiritual principles: but at all events he asked himself the question, and gave an answer. We shall investigate this answer by arranging what Leibniz has said under the heads of: matter as a metaphysical principle; matter as a physical phenomenon; and the relation of phenomena to absolute reality, or of the physical to the metaphysical. In connection with the second head, particularly, we shall find it necessary to discuss what Leibniz has said about s.p.a.ce, time, and motion.

Wolff, who put the ideas of Leibniz into systematic shape, did it at the expense of almost all their significance. He took away the air of paradox, of remoteness, that characterized Leibniz's thought, and gave it a popular form. But its depth and suggestiveness vanished in the process. Unfortunately, Wolff's presentations of the philosophy of Leibniz have been followed by others, to whom it seemed a dull task to follow out the intricacies of a thought nowhere systematically expressed. This has been especially the case as concerns the Leibnizian doctrine of matter. A superficial interpretation of certain pa.s.sages in Leibniz has led to an almost universal misunderstanding about it. Leibniz frequently says that since matter is composite or complex, it follows that there must be something simple as its basis, and this simple something is the monad. The misinterpretation just spoken of consists in supposing that Leibniz meant that matter as composite is made up of monads as simple; that the monad and matter are facts of the same order, the latter being only an aggregate, or continued collection of the former. It interpreted the conception of Leibniz in strict a.n.a.logy with the atomic theory of Lucretius, excepting that it granted that the former taught that the ultimate atom, the component of all complex forms of matter, has position only, not extension, its essence consisting in its exercise of force, not in its mere s.p.a.ce occupancy. The monad was thus considered to be _in_ s.p.a.ce, or at least conditioned by s.p.a.ce relations, as is a mathematical point, although not itself spatial in the sense of being extended. Monad and matter were thus represented as facts of the same kind or genus, having their difference only in their relative isolation or aggregation.

But Leibniz repudiated this idea, and that not only by the spirit of his teaching, but in express words. Monads "are not ingredients or const.i.tuents of matter," he says, "but only _conditions_ of it." "Monads can no more be said to be parts of bodies, or to come in contact with them, or to compose them, than can souls or mathematical points." "Monads _per se_ have _no_ situation relative to one another." An increase in the number of created monads, he says again, if such a thing could be supposed, would no more increase the amount of matter in existence, than mathematical points added to a line would increase its length. And again: "There is no nearness or remoteness among monads; to say that they are gathered in a point or are scattered in s.p.a.ce, is to employ mental fictions, _in trying to imagine what can only be thought_." The italicized words give the clew to the whole discussion. To make monads of the same order as corporeal phenomena, is to make them sensible, or capable of being imaged, or conditioned by s.p.a.ce and time,--three phrases which are strictly correlative. But the monads can only be thought,--that is, their qualities are ideal, not sensible; they can be realized only by reason, not projected in forms having spatial outline and temporal habitation, that is, in images. Monads and material things, in other words, are facts of two distinct orders; they are related as the rational or spiritual and the physical or sensible. Matter is no more composed of monads than it is of thoughts or of logical principles. As Leibniz says over and over again: Matter, s.p.a.ce, time, motion are only phenomena, although phenomena _bene fundata_,--phenomena, that is, having their rational basis and condition. The monads, on the other hand, are not appearances, they are realities.

Having freed our minds from the supposition that it is in any way possible to form an image or picture of the monad; having realized that it is wholly false to suppose that monads occupy position in s.p.a.ce, and then by their continuity fill it, and make extended matter,--we must attempt to frame a correct theory of the nature of matter and its relation to the monad. We shall do this only as we realize that "matter," so far as it has any reality, or so far as it has any real _fundamentum_, must be something ideal, or, in Leibniz's language, "metaphysical." As he says over and over again, the only realities are the substances or spiritual units of activity, to which the name "monad" is given. In the inquiry, then, after such reality as matter may have, we must betake ourselves to this unit of living energy.

Although every monad is active, it is not entirely active. There is, as we have already seen, an infinite scale of substances; and since substance is equivalent to activity, this is saying that there is an infinite scale of activities. G.o.d alone is _purus actus_, absolute energy, untouched by pa.s.sivity or receptivity. Every other being has the element of incompleteness, of inadequacy; it does not completely represent the universe. In this pa.s.sivity consists its finitude, so that Leibniz says that not even G.o.d himself could deprive monads of it, for this would be to make them equal to himself. In this pa.s.sivity, incompleteness, or finitude, consists what we call matter. Leibniz says that he can understand what Plato meant when he called matter something essentially imperfect and transitory. Every finite monad is a union of two principles,--those of activity and of pa.s.sivity. "I do not admit,"

says Leibniz, "that there are souls existing simply by themselves, or that there are created spirits detached from all body. G.o.d alone is above all matter, since he is its author; creatures freed from matter would be at the same time detached from the universal connection of things, and, as it were, deserters from the general order." And again, "Beings have a nature which is both active and pa.s.sive; _that is_, material and immaterial." And again, he says that every created monad requires both an entelechy, or principle of activity, and matter. "Matter is essential to any entelechy, and can never be separated from it, since matter _completes_ it." In short, the term "monad" is equivalent to the term "entelechy" only when applied to G.o.d. In every other monad, the entelechy, or energy, is but one factor. "Matter, or primitive pa.s.sive power, completes the entelechy, or primitive active power, so that it becomes a perfect substance, or monad." On the other hand, of course, matter, as the pa.s.sive principle, is a mere potentiality or abstraction, considered in itself. It is real only in its union with the active principle. Matter, he says, "cannot exist without immaterial substances." "To every particular portion of matter belongs a particular _form_; that is, a soul, a spirit." To this element of matter, considered as an abstraction, in its distinction from soul, Leibniz, following the scholastics, and ultimately Aristotle, gives the name, "first" or "bare" matter. The same influence is seen in the fact that he opposes this element of matter to "form," or the active principle.

Our starting-point, therefore, for the consideration of matter is the statement that it is receptivity, the capacity for being affected, which always const.i.tutes matter. But what is meant by "receptivity"? To answer this question we must return to what was said about the two activities of the monad,--representation, or perception, and appet.i.tion,--and to the difference between confused and distinct ideas. The monad has appet.i.tion so far as it determines itself from within to change, so far as it follows an internal principle of energy. It is representative so far as it is determined from without, so far as it receives impressions from the universe. Yet we have learned to know that in one sense everything occurs from the spontaneity of the monad itself; it receives no influence or influxus from without; everything comes from its own depths, or is appet.i.tion. But, on the other hand, all that which so comes forth is only a mirroring or copying of the universe. The whole content of the appet.i.tion is representation. Although the monad works spontaneously, it is none the less determined in its activities to produce only reflections or images of the world. In this way appet.i.tion and representation appear to be identical. The monad is determined from within, indeed, but it is determined to exactly the same results as if wholly determined from without. What light, then, can be thrown from this distinction upon the nature of matter?

None, unless we follow Leibniz somewhat farther. If we do, we shall see that the soul is regarded as appet.i.tive, or self-active, so far as it has clear and distinct ideas. If the monad reaches distinct consciousness, it has knowledge of self,--that is, of the nature of pure spirit,--or, what again is equivalent to this, of the nature of reality as it universally is. Such knowledge is knowledge of G.o.d, of substance, of unity, of pure activity, and of all the innate ideas which elevate the confused perceptions of sense into science. Distinct consciousness is therefore equivalent to self-activity, and this to recognition of G.o.d and the universal. But if knowledge is confused, it is not possible to see it in its relations to self; it cannot be a.n.a.lyzed; the rational or ideal element in it is concealed from view. In confused ideas, therefore, the soul appears to be pa.s.sive; being pa.s.sive, to be determined from without. This determination from without is equivalent to that which is opposed to spirit or reason, and hence appears as matter. Such is in outline the Leibnizian philosophy.

It thus is clear that merely stating that matter is pa.s.sivity in the monad is not the ultimate way of stating its nature. For pa.s.sivity means in reality nothing but confused representations,--representations, that is, whose significance is not perceived. The true significance of every representation is found in its relation to the ego, or pure self-activity, which, through its dependent relation upon G.o.d, the absolute self-activity and ego, produces the representation from its own ideal being. So far as the soul does not have distinct recognition of relation of all representations to self, it feels them as coming from without; as foreign to spirit; in short, as matter. Leibniz thus employs exactly the same language about confused ideas that he does about pa.s.sivity, or matter. It is not possible that the monad should have distinct consciousness of itself as a mirror of the whole universe, he says, "for in that case every entelechy would be G.o.d." Again, "the soul would be G.o.d if it could enter at once and with distinctness into everything occurring within it." But it is necessary "that we should have pa.s.sions which consist in confused ideas, in which there is something involuntary and unknown, and which represent the body and const.i.tute our imperfection." Again, he speaks of matter as "the _mixture_ (_melange_) of the effects of the infinite environing us." In that expression is summed up his whole theory of matter. It is a mixture; it is, that is to say, confused, aggregated, irresolvable into simple ideas. But it is a mixture of "effects of the infinite about us;"

that is, it takes its rise in the true, the real, the spiritual. It only fails to represent this as it actually is. Matter, in short, is a phenomenon dependent upon inability to realize the entire spiritual character of reality. It is spirit apprehended in a confused, hesitating, and pa.s.sive manner.

It is none the less a necessary phenomenon, for it is involved in the idea of a continuous gradation of monads, in the distinction between the infinite and the finite, or, as Leibniz often prefers to put it, between the "creator" and the "created." There is involved everywhere in the idea of Leibniz the conception of subordination; of a hierarchy of forms, each of which receives the law of its action from the next higher, and gives the law to the next lower. We have previously considered the element of pa.s.sivity or receptivity as relating only to the monad which manifests it. It is evident, however, that what is pa.s.sive in one, implies something active in another. What one receives, is what another gives. The reciprocal influence of monads upon one another, therefore, as harmonious members of one system, requires matter. More strictly speaking, this reciprocal influence _is_ matter. To take away all receptivity, all pa.s.sivity, from monads would be to isolate them from all relations with others; it would be to deprive them of all power of affecting or being affected by others. That is what Leibniz meant by the expression already quoted, that if monads had not matter as an element in them, "they would be, as it were, deserters from the general order." The note of unity, of organic connection, which we found to be the essence of the Leibnizian philosophy, absolutely requires, therefore, matter, or pa.s.sivity.

It must be remembered that this reciprocal influence is ideal. As Leibniz remarks, "When it is said that one monad is affected by another, this is to be understood concerning its _representation_ of the other. For the Author of things has so accommodated them to one another that one is said to suffer (or receive from the other) when its relative value gives way to that of the other." Or again, "the modifications of one monad are the ideal causes of the modifications of another monad, so far as there appear in one the reasons on account of which G.o.d brought about in the beginning certain modifications in another." And most definitely of all: "A creature is called active so far as it has perfection; pa.s.sive in so far as it is imperfect. One creature is more perfect than another so far as there is found in it that which serves to _render the reason_, _a priori_, for that occurring in the other; and it is in this way that it acts upon the other."

We are thus introduced, from a new point of view and in a more concrete way, to the conception of pre-established harmony. The activity of one, the energy which gives the law to the other and makes it subordinate in the hierarchy of monads, is conceived necessarily as spirit, as soul; that which receives, which is rendered subordinate by the activity of the other, is body. The pre-established harmony is the fact that they are so related that one can receive the law of its activity from the other. Leibniz is without doubt partially responsible for the ordinary misconception of his views upon this point by reason of the ill.u.s.tration which he was accustomed to use; namely, of two clocks so constructed that without any subsequent regulation each always kept perfect time with the other,--as much so as if there were some actual physical connection between them. This seems to put soul and body, spirit and matter, as two co-ordinate substances, on the same level, with such natural opposition between them that some external harmony must arrange some unity of action. In causing this common idea of his theory of pre-established harmony, Leibniz has paid the penalty for attempting to do what he often reproves in others,--imagining or presenting in sensible form what can only be thought. But his other explanations show clearly enough that the pre-established harmony expresses, not a relation between two parallel substances, but a condition of dependence of lower forms of activity upon the higher for the law of their existence and activity,--in modern terms, it expresses the fact that phenomena are conditioned upon noumena; that material facts get their significance and share of reality through their relation to spirit.

We may sum up what has been said about matter as an element in the monad, or as a metaphysical principle, as follows: The existence of matter is not only not opposed to the fundamental ideas of Leibniz, but is a necessary deduction from them. It is a necessity of the principle of continuity; for this requires an infinity of monads, alike indeed in the universal law of their being, but unlike, each to each, in the specific coloring or manifestation of this law. The principle of organic unity requires that there be as many real beings as possible partic.i.p.ating in and contributing to it. It is necessary, again, in order that there may be reciprocal influence or connection among the monads. Were it not for the material element in the monad, each would be a G.o.d; if each were thus infinite and absolute, there would be so many principles wholly independent and isolated. The principle of harmony would be violated. So much for the necessity of the material factor. As to its nature, it is a principle of pa.s.sivity; that is, of ideal receptivity, of conformity to a law apparently not self-imposed, but externally laid down. This makes matter equivalent to a phenomenon; that is to say, to the having of confused, imperfect, inadequate ideas. To say that matter is correlative to confused ideas is to say that there is no recognition of its relation to self or to spirit. As Leibniz sometimes puts it, since there is an infinity of beings in the universe, each one of which exercises an ideal influence upon every other one of the series, it is impossible that this other one should realize their full meaning; they appear only as confused ideas, or as matter. To use language which Leibniz indeed does not employ, but which seems to convey his thought, the spirit, not seeing them as they really are, does not _find_ itself in them. But matter is thus not only the confused manifestation or phenomenon of spirit, it is also its potentiality. Pa.s.sivity is always relative. It does not mean complete lack of activity; that, as Leibniz says, is nothingness, and matter is not a form of nothingness. Leibniz even speaks of it as pa.s.sive _power_. That is to say, there is an undeveloped or incomplete activity in what appears as matter, and this may be,--if we admit an infinity of time,--must be developed. When developed it manifests itself as it really is, as spirit. Confused ideas, as Leibniz takes pains to state, are not a genus of ideas ant.i.thetical to distinct; they differ only in degree or grade. They are on their way to become distinct, or else they are distinct ideas which have fallen back into an "involved" state of being. Matter, therefore, is not absolutely opposed to spirit,--on the one hand because it is the manifestation, the phenomenon, of spirit; on the other, because it is the potentiality of spirit, capable of sometime realizing the whole activity implied in it, but now latent.

Thus it is that Leibniz says that everything is "full" of souls or monads. What appears to be lifeless is in reality like a pond full of fishes, like a drop of water full of infusoria. Everything is organic down to the last element. More truly, there is no last element. There is a true infinity of organic beings wrapped up in the slightest speck of apparently lifeless matter. These ill.u.s.trations, like many others which Leibniz uses, are apt to suggest that erroneous conception of the relation of monads to spirit which we were obliged, in Leibniz's name, to correct at the outset,--the idea, namely, that matter is composed, in a spatial or mechanical way, of monads. But after the foregoing explanations we can see that what Leibniz means when he says that every portion of matter is full of entelechies or souls, like a garden full of plants, is that there is an absolute continuity of spiritual principles, each having its ideal relation with every other. There is no point of matter which does not represent in a confused way the entire universe. It is therefore as infinite in its activities as the universe. In idea also it is capable of representing in distinct consciousness, or as a development of its own self-activity, each of these infinite activities.

In a word, every created or finite being may be regarded as matter or as spirit, according as it is accounted for by its external relations, as the reasons for what happen in it are to be found elsewhere than in its own explicit activity, or according as it shows clearly in itself the reasons for its own modifications, and also accounts for changes occurring in other beings. The externally conditioned is matter; the internally conditioned, the self-explanatory, is self-active, or spirit. Since all external relations are finally dependent on organic; since the ultimate source of all explanation must be that which is its own reason; since the ultimate source of all activity must be that which is self-active,--the final reason or source of matter is spirit.

CHAPTER VIII.

MATERIAL PHENOMENA AND THEIR REALITY.

We have seen the necessity and nature of matter as deductions from the fundamental principles of Leibniz. We have seen that matter is a phenomenon or manifestation of spirit in an imperfect and confused way. But why should it appear as moving, as extended, as resisting, as having cohesion, with all the concrete qualities which always mark it? Is there any connection between these particular properties of matter as physical, and its "metaphysical" or ideal character? These are the questions which now occupy us. Stated more definitely, they take the following form: Is there any essential connection between the properties of matter as a metaphysical element, and its properties as a sensible fact of experience? Leibniz holds that there is. He does not, indeed, explicitly take the ground that we can deduce _a priori_ all the characteristics of matter as a fact of actual experience from its rational notion, but he thinks we can find a certain a.n.a.logy between the two, that the sensible qualities are images or reflexes of the spiritual qualities, witnessing, so far as possible, to their origin in pure energy.

His position is as follows: that which in the monad is activity or substantial, is, in sensible matter, motion. That which in the monad is lack of a given activity, that which const.i.tutes its subordinate position in the hierarchy of monads, is, in the sphere of material things, inertia. That which in the spiritual world is the individuality of monads, making each forever ideally distinct from every other, is, in the phenomenal realm, resistance or impenetrability. The perfect continuity of monads in the _mundus intelligibilis_ has also its counterpart in the _mundus sensibilis_ in the diffusion or extension of physical things.

Instead of following out this a.n.a.logy directly, it will rather be found convenient to take up Leibniz's thought in its historical connection. We have already alluded to the fact that he began as a Cartesian, and that one of the first ideas which repelled him from that system of thought was the notion that the essence of matter is extension. His earliest philosophical writings, as he was gradually coming to the thoughts which thereafter dominated him, are upon this point. In general, his conclusions are as follows: If matter were extension, it would be incapable of pa.s.sion or of action. Solidity, too, is a notion entirely opposed to the conception of mere extension. The idea of matter as extension contradicts some of the known laws of motion. It requires that the quant.i.ty of motion remain unchanged whenever two bodies come in contact, while as matter of fact it is the quant.i.ty of energy, that which the motion is capable of effecting, that remains unchanged; or, as he more often puts the objection, the Cartesian notion of matter requires that matter be wholly indifferent to motion, that there be nothing in it which resists motion when imparted. But, says Leibniz, there is something resisting, that to which Keppler gave the name "inertia." It is not found to be true if one body impacts upon another that the second moves without diminis.h.i.+ng the velocity or changing the direction of the first. On the other hand, just in proportion to the size of the second body, it resists and changes the motion of the first, up to the point of causing the first to rebound if small in comparison. And when it was replied that the r.e.t.a.r.dation was due to the fact that the force moving the first body had now to be divided between two, Leibniz answered that this was simply to give up the contention, and besides the notion of extension to use that of force. If extension were the essence of matter, it should be possible to deduce all the properties of matter, or at least to account for them all, from it. But since, as just seen, this does not enable us to account for any of them, since for any of its concrete qualities we have to fall back on force, it is evident where the true essence of matter is to be found.

Leibniz has another argument of a logical nature, as those already referred to are of a physical: "Those who claim that extension is a substance, reverse the order of words as well as of thoughts. Besides extension there must be a subject which is extended; that is to say, something to which it belongs to be repeated or continued. For extension is nothing but a repet.i.tion or continued multiplication of that which is spread out,--it is a plurality, a continuity, a co-existence of parts. Consequently, extension does not suffice to explain the nature of the repeated or manifold substance, of which the notion is anterior to that of its repet.i.tion." Extension, in other words, is nothing substantial, it is not something which can exist by itself; it is only a quality, a property, a mode of being. It is always relative to something which has extension. As Leibniz says elsewhere: "I insist that extension is only an _abstraction_, and requires something which is extended. It presupposes some quality, some attribute, some nature in a subject which is extended, diffused, or continued. Extension is a diffusion of this quality. For example, in milk there is an extension or diffusion of whiteness; in the diamond an extension or diffusion of hardness; in body in general a diffusion of ant.i.typia or materiality. There is accordingly in body something anterior to extension."

From the physical side, therefore, we find it impossible to account for the concrete properties of material phenomena from extension; on the logical we find that the idea of extension is always relative to that which is extended. What is that which is to be considered as the bearer of extension and the source of physical qualities? We are led back to the point at which we left the matter in the last chapter. It is force, and force both pa.s.sive and active. Leibniz uses the term "matter" in at least three senses: it is the metaphysical element of pa.s.sive force _in_ the monad; it is the monad itself considered as, upon the whole, externally conditioned or unconscious; and it is the phenomenon resulting from the aggregation of the monads in the second sense. The first is naked matter, and is a pure abstraction; the second is the monad as material, as opposed to the monad, as soul; the third is clothed, or second matter, or, concretely, body, _corpus_. The first is unreal by itself; the second is one phase of substance; the third is not substantial, but is a reality, though a phenomenal one. It is from the substantial monad that we are to explain the two things now demanding explanation,--that element in _bodies_ (matter in third sense) which is the source of their physical properties, and that which is the subject, the carrier, so to speak, of extension.

That of which we are in search as the source of the physical qualities of bodies is motion. This is not force, but its "image." It is force, says Leibniz, that "is the real element in motion; that is to say, it is that element which out of the present state induces a change in the future state." As force, in other words, is the causal activity which effects the development of one "representation" of a monad out of another, so motion, in the realm of phenomena, is not only change, but change which is continuous and progressive, each new position being dependent upon the foregoing, and following out of it absolutely without break.

Motion, therefore, is the manifestation of the ideal unity of substance,--a unity not of mere static inherence, but of a continuous process of activity. It is from this standpoint that Leibniz accounts for the so-called transference of motion from one body to another upon contact. The ordinary view of this, which looks at it as if one body loses the motion which another body gains, Leibniz ridicules, saying that those who hold this view seem to think that motion is a kind of thing, resembling, perchance, salt dissolved in water. The right view, on the other hand, does away with all appearance of mystery in the carrying over of motion from one body to another, for it recognizes that continuity is the very essence of motion, and that we do not have two things and a third process, but that the two bodies are phases or elements in one and the same system of movement.

Starting from this idea of motion, then, Leibniz is to account for the actual qualities of matter as found in experience. These are the form, magnitude, cohesion, resistance, and the purely sensible qualities of objects. "First" matter, that is, abstract matter, may be conceived, according to Leibniz, as perfectly h.o.m.ogeneous, a "subtle fluid," in his words, without any distinction of parts or of solidity. But this _is_ an abstract notion. It is what matter would be without motion. Motion necessarily differentiates this plenum of h.o.m.ogeneity, and thus causes distinctions of figure (that is, boundaries of parts) and varieties of cohesion, or the varying solidity and fluidity of bodies. The latter difference is indeed the ultimate one. The principle of continuity or gradation, as applied to motion, makes it necessary that motions should not be in any two places of exactly the same energy. The result is that the original fluid matter is everywhere differently divided. Motion, entering into the uniform plenum, introduces distinction; it causes so much of the matter as is affected by a given movement to collect together and form in appearance a coherent body, as opposed to surrounding bodies which are affected by different degrees of energy. But even this is only approximate; the same principle of continuity must be applied within any apparently coherent body; its parts, while, in relation to other bodies, they have the same amount of motion, are in relation to one another differently affected. There are no two having exactly the same motion; if they had, there would be no distinction between them; and thus, according to the principle of Leibniz, they would be the same.

It follows at once from this that there is in the universe no body of absolute hardness or solidity, nor of entire softness or fluidity. A perfectly solid body would be one whose system of motions could not be affected by any other system,--a body which by motion had separated itself from motion, or become absolute. This is evidently an idea which contradicts itself, for the very essence of motion is continuity or relation. A body perfectly fluid, on the other hand, would be one in which there was no resistance offered to other motions,--a body, in other words, in which there are no movements that, entering into connection with one another, form a relative opposition to other movements. It would be a body isolated or out of relation with the general system of motions, and hence an impossibility. There is no last term either of solidity or of fluidity.

It equally follows as matter of course that there is no indivisible particle of matter,--no atom. The infinity of degrees of motion implies a corresponding division of matter. As already said, it is only in contrast with other relatively constant systems of motion that any body is of uniform motion; in reality there is everywhere throughout it variety of movement, and hence complete divisibility, or rather, complete division. If Leibniz were to employ the term "atom"

at all, it could be only in the sense of the modern dynamical theory (of which, indeed, he is one of the originators), according to which the atom is not defined by its spatial position and outlines, but, by the range of its effects, as the centre of energies of infinite circ.u.mference. Correlative to the non-existence of the atom is the non-existence of the vacuum. The two imply each other. The hard, limited, isolated body, having no intrinsic relations with other bodies, must have room to come into external relations with them. This empty s.p.a.ce, which is the theatre of such accidental contacts as may happen, is the vacuum. But if bodies are originally in connection with one another, if they are in reality but differentiations of varying degrees of motion within one system of motion, then there is no necessity for the vacuum,--nay, there is no place for it. The vacuum in this case could mean only a break, a chasm, in the order of nature. According to the theory of Leibniz, "bodies" are but the dynamic divisions of the one energy that fills the universe; their separateness is not an independent possession of any one of them or of all together, but is the result of relations to the entire system. Their apparent isolation is only by reason of their actual connections. To admit a vacuum anywhere, would thus be to deny the relatedness of the parts separated by it. The theory of the atom and the vacuum are the two phases of the metaphysical a.s.sumption of an indefinite plurality of independent separate realities. The theory of Leibniz, resting as it does on the idea of a perfect unity of interrelated members, must deny both of these aspects. Were we making an extended a.n.a.lysis of the opposed view, it would be necessary to point out that it denies itself. For it is only _through_ the vacuum that the atoms are isolated or independent, and the sole function of the vacuum is to serve as the background of the atoms. The atoms are separated only in virtue of their connection, and the vacuum is what it is--pure emptiness--only on account of that which is in it. In short, the theory is only an abstract and incomplete way of grasping the thought of relation or mediated unity.

We have thus discovered that all motions conspire together, or form a system. But in their unity they do not cease to be motions, or variously differentiated members. Through this differentiation, or mutual reaction of motions, there comes about the appearance of boundaries, of separation. From these boundaries or terminations arise the form and size of bodies. From motion also proceeds the cohesion of bodies, in the sense that each relative system resists dissolution, or hangs together. Says Leibniz, "The motions, since they are conspiring, would be troubled by separation; and accordingly this can be accomplished only by violence and with resistance." Not only form, size, and stability depend upon motion, but also the sensible, the "secondary" qualities. "It must not be supposed that color, pain, sound, etc., are arbitrary and without relation to their causes. It is not G.o.d's way to act with so little reason and order. There is a kind of resemblance, not entire, but of relation, of order. We say, for example, 'Light is in the fire,' since there are motions in the fire which are imperceptible in their separation, but which are sensible in their conjunction or confusion; and this is what is made known in the idea of light." In other words, color, sound, etc., even pain, are still the perception of motion, but in a confused way. We thus see how thoroughly Leibniz carries back all the properties of bodies to motion. To sum up, motion is the origin of the relative solidity, the divisibleness, the form, the size, the cohesion, or active resistance of bodies, and of their properties as made known to us in immediate sensation.

In all that has been said it has been implied that extension is already in existence; "first matter" is supposed to fill all s.p.a.ce, and motion to determine it to take upon itself its actual concrete properties. But this "first matter," when thus spoken of, has a somewhat mythological sound, even if it be admitted that it is an abstraction. For how can an abstraction be extended in s.p.a.ce, and how can it form, as it were, a background upon which motion displays itself? The idea of "first matter" in its relation to extension evidently demands explanation. In seeking this explanation we shall also learn about that "subject" which Leibniz said was necessarily presupposed in extension, as a concrete thing is required for a quality.

The clew to the view of Leibniz upon this point may be derived, I think, from the following quotations:--

"If it were possible to see what makes extension, that kind of extension which falls under our eyes at present would vanish, and our minds would perceive nothing else than simple realities existing in mutual externality to one another. It would be as if we could distinguish the minute particles of matter variously disposed from which a painted image is formed: if we could do it, the image, which is nothing but a phenomenon, would vanish... . If we think of two simple realities as both existing at the same time, but distinct from one another, we look at them as if they were outside of one another, and hence conceive them as extended."

The monads are outside of one another, not spatially, but ideally; but this reciprocal distinction from one another, if it is to appear in phenomenal mode, must take the form of an image, and the image is spatial. But if the monads were pure activity, they would _not_ take phenomenal form or appear in an image. They would always be thought just as they are,--unextended activities realizing the spiritual essence of the universe. But they are not pure activity; they are pa.s.sive as well. It is in virtue of this pa.s.sive element that the ideal externality takes upon itself phenomenal or sensible form, and thus appears as spatial externality.

Leibniz, in a pa.s.sage already quoted, refers to the diffusion of materiality or _ant.i.typia_. This word, which is of frequent occurrence in the discussions of Leibniz, he translates generally as "impenetrability," sometimes as "pa.s.sive resistance." It corresponds to the solidity or resistance of which Locke spoke as forming the essence of matter. Ant.i.typia is the representation by a monad of the pa.s.sive element in other monads. Leibniz sometimes speaks as if all created monads had in themselves ant.i.typia, and hence extension; but he more accurately expresses it by saying that they need (_exigent_) it. This is a technical term which he elsewhere uses to express the relation of the possible to the actual. The possible "needs" the actual, not in the sense that it _necessarily_ requires existence, but in the sense that when the actual gives it existence, it is the logical basis of the actual,--the actual, on the other hand, being its real complement. The pa.s.sivity of the monad is therefore at once the logical basis and the possibility of the impenetrability of matter. It is owing to the pa.s.sivity of the monad that it does not adequately reflect (that it is not transparent to, so to speak) the activities of other monads. In its irresponsiveness, it fails to mirror them in itself. It may be said, therefore, to be impenetrable to them. They in turn, so far as they are pa.s.sive, are impenetrable to it. Now the impenetrable is, _ex vi terminis_, that which excludes, and that which excludes, not in virtue of its active elasticity, but in virtue of its mere inertia, its dead weight, as it were, of resistance. But mutual exclusion of this pa.s.sive sort const.i.tutes that which is extended. Extension is the abstract quality of this concrete subject. Such, in effect, is the deduction which Leibniz gives of body, or physical matter, from matter as metaphysical; of matter as sensible or phenomenal, from matter as ideal or as intelligible.

If we put together what has been said, it is clear that material phenomena (bodies, _corpora_, in Leibniz's phrase) simply repeat in another sphere the properties of the spiritual monad. There is a complete parallelism between every property, each to each, and this necessarily; for every property of "body" is in logical dependence upon, and a phenomenalization of, some spiritual or ideal quality. Motion is the source of all the dynamic qualities of body, and motion is the reflection of Force, that force which is Life. But this force in all finite forms is conditioned by a pa.s.sive, unreceptive, unresponsive factor; and this must also have its correlate in "body." This correlate is primarily impenetrability, and secondarily extension. Thus it is that concrete body always manifests motion, indeed, but upon a background of extension, and against inertia. It never has free play; had it an unrestrained field of activity, extension would disappear, and spatial motion would vanish into ideal energy. On the other hand, were the essence of matter found in resistance or impenetrability, it would be wholly inert; it would be a monotone of extension, without variety of form or cohesion. As Leibniz puts it with reference to Locke, "body" implies motion, or impetuosity, resistance, and cohesion. Motion is the active principle, resistance the pa.s.sive; while cohesion, with its various grades of completeness, which produce form, size, and solidity, is the result of their union.

Leibniz, like Plato, has an intermediary between the rational and the sensible; and as Plato found that it was mathematical relations that mediate between the permanent and unified Ideas and the changing manifold objects, so Leibniz found that the relations of s.p.a.ce and time form the natural transition from the sphere of monads to the world of bodies. As Plato found that it was the possibility of applying mathematical considerations to the world of images that showed the partic.i.p.ation of Ideas in them, and const.i.tuted such reality as they had, so Leibniz found that s.p.a.ce and time formed the element of order and regularity among sense phenomena, and thus brought them into kins.h.i.+p with the monads and made them subjects of science. It is implied in what is here said that Leibniz distinguished between s.p.a.ce and time on the one hand, and duration and extension on the other. This distinction, which Leibniz draws repeatedly and with great care, has been generally overlooked by his commentators. But it is evident that this leaves Leibniz in a bad plight. Mathematics, in its various forms, is the science of spatial and temporal relations. But if these are identical with the forms of duration and extension, they are purely phenomenal and sensible. The science of them, according to the Leibnizian distinction between the absolutely real and the phenomenally real, would be then a science of the confused, the imperfect, and the transitory; in fact, no science at all. But mathematics, on the contrary, is to Leibniz the type of demonstrative, conclusive science. s.p.a.ce and time are, in his own words, "innate ideas," and the entire science of them is the drawing out of the content of these innate--that is, rational, distinct, and eternal--ideas. But extension and duration are sensible experiences; not rational, but phenomenal; not distinct, but confused; not eternal, but evanescent. We may be sure that this contradiction would not escape Leibniz, although it has many of his critics and historians.

It is true, however, that he occasionally uses the terms as synonymous; but this where the distinction between them has no bearing on the argument in hand, and where the context determines in what sense the term is used. The distinction which he actually makes, and to which he keeps when s.p.a.ce and time are the subject of discussion, is that extension and duration are qualities or predicates of objects and events, while s.p.a.ce and time are relations, or orders of existence. Extension and duration are, as he says, the _immensity_, the ma.s.s, the continuation, the repet.i.tion, of some underlying subject. But s.p.a.ce and time are the _measure_ of the ma.s.s, the rule or law of the continuation, the order or mode of the repet.i.tion. Thus immediately after the pa.s.sage already quoted, in which he says that extension in body is the diffusion of materiality, just as whiteness is the diffusion of a property of milk, he goes on to say "that extension is to s.p.a.ce as duration to time. Duration and extension are attributes of things; but s.p.a.ce and time are to be considered, as it were, outside of things, and as serving to measure them." Still more definitely he says: "Many confound the immensity or extent of things with the s.p.a.ce by means of which this extent is defined. s.p.a.ce is not the extension of body, any more than duration is its time. Things keep their extension, not always their s.p.a.ce. Everything has its own extent and duration; but it does not have a time of its own, nor keep for its own a s.p.a.ce." Or, as he expresses the latter idea elsewhere, s.p.a.ce is like number, in the sense that it is indifferent to spatial things, just as number is indifferent to _res numerata_. Just as the number five is not a quality or possession of any object, or group of objects, but expresses an order or relation among them, so a given s.p.a.ce is not the property of a thing, but expresses the order of its parts to one another. But extension, on the other hand, is a property of the given objects. While extension, therefore, must always belong to some actual thing, s.p.a.ce, as a relation, is as applicable to possible things as to actual existences; so that Leibniz sometimes says that time and s.p.a.ce "express possibilities." They are that which makes it possible for a definite and coherent order of experiences to exist. They determine existence in some of its relations, and as such are logically prior to any given forms of existence; while extent and duration are always qualities of some given form of existence, and hence logically derivative. Since time and s.p.a.ce "characterize possibilities" as well as actualities, it follows as a matter of course "that they are of the nature of eternal truths, which relate equally to the possible and to the existing." Being an eternal truth, s.p.a.ce must have its place in that which is simply the active unity of all eternal truths,--the mind of G.o.d. "Its truth and reality are based upon G.o.d. It is an order whose source is G.o.d." Since G.o.d is _purus actus_, he is the immediate, the efficient source only of that which partakes in some degree of his own nature, or is rational; and here is another clear point of distinction between s.p.a.ce and extension, between time and duration.

But we must ask more in detail regarding their nature. Admitting that they are relations, ideal and prior to particular experiences, the question must be asked, What sort of relations are they; how are they connected with the purely spiritual on one hand, and with the phenomenal on the other? Leibniz's most extended answers to these questions are given in his controversy with Clarke. The latter took much the same position regarding the nature of s.p.a.ce (though not, indeed, concerning the origin of its idea) as Locke, and the arguments which Leibniz uses against him he might also have used, for the most part, against Locke. Locke and Clarke both conceived of s.p.a.ce and time as wholly without intrinsic relation to objects and events. It is especially against this position that Leibniz argues, holding that s.p.a.ce and time are simply orders or relations of objects and events, that s.p.a.ce exists only where objects are existing, and that it is the order of their co-existence, or of their possible co-existence; while time exists only as events are occurring, and is the relation of their succession. Clarke, on the other hand, speaks of the universe of objects as bounded by and moving about in an empty s.p.a.ce, and says that time existed before G.o.d created the finite world, so that the world came into a time already there to receive its on-goings, just as it fell into a s.p.a.ce already there to receive its co-existences.

To get at the ideas of Leibniz, therefore, we cannot do better than follow the course of this discussion. He begins by saying that both s.p.a.ce and time are purely relative, one being the order of co-existences, the other of successions. s.p.a.ce characterizes in terms of possibility an order of things existing at the same time, so far as they exist in mutual relations (_ensemble_), without regard to their special modes of existence. As to the alternate doctrine that s.p.a.ce is a substance, or something absolute, it contradicts the principle of sufficient reason. Were s.p.a.ce something absolutely uniform, without things placed in it, there would be no difference between one part and another, and it would be a matter of utter indifference to G.o.d why he gave bodies certain positions in s.p.a.ce rather than others; similarly it would be a matter of indifference why he created the world when he did, if time were something independent of events. In other words, the supposed absoluteness of s.p.a.ce and time would render the action of G.o.d wholly without reason, capricious, and at haphazard. Similarly, it contradicts the principle of "indiscernibles," by which Leibniz means the principle of specification, or distinction. According to him, to suppose two things exactly alike, is simply to imagine the same thing twice. Absolute uniformity, wholly undifferentiated, is a fiction impossible to realize in thought. "s.p.a.ce considered without objects has nothing in it to determine it; it is accordingly nothing actual. The parts of s.p.a.ce must be determined and distinguished by the objects which are in them." Finally, were s.p.a.ce and time absolutely real things in themselves, they would be independent of G.o.d, and even limitations upon him. "They would be more substantial than substances. G.o.d would not be able to change or destroy them. They would be immutable and eternal in every part. Thus there would be an infinity of eternal things (these parts) independent of G.o.d." They would limit G.o.d because he would be obliged to exist _in_ them. Only by existing through this independent time would he be eternal; only by extending through this independent s.p.a.ce would he be omnipresent. s.p.a.ce and time thus become G.o.ds themselves.

When Clarke declares that by the absoluteness of s.p.a.ce and time he does not mean that they are themselves substances, but only properties, attributes of substance, Leibniz advances the same arguments in different form. If s.p.a.ce were the property of the things that are in s.p.a.ce, it would belong now to one substance, now to another, and when empty of all material substance, even to an immaterial substance, perhaps to G.o.d. "Truly a strange attribute which is handed about from one thing to another. Substances thus leave their accidents as if they were old clothes, and other substances put them on." Since these finite s.p.a.ces are in infinite s.p.a.ce, and the latter is an attribute of G.o.d, it must be that an attribute of G.o.d is composed of parts, some of them empty, some full, some round, some square. So, too, whatever is in time would help make one of the attributes of G.o.d. "Truly a strange G.o.d,"

says Leibniz, "this Deity of parts" (_ce Dieu a parties_). Clarke's reply to this was that s.p.a.ce and time are attributes of G.o.d and of G.o.d alone, not of things in s.p.a.ce and time,--that, indeed, strictly speaking, there are no parts in s.p.a.ce or in time; they are absolutely one. This was virtually to give up the whole matter. It was to deny the existence of finite s.p.a.ces and times, and to resolve them into an indefinite attribute of G.o.d. Such a view, as Leibniz points out, not only is contrary to experience, but affords no aid in determining the actual concrete forms and situations of bodies, and durations and successions of events. The absolute s.p.a.ce and time, having no parts, are wholly out of relations to these concrete existences. The latter require, therefore, a s.p.a.ce and a time that are relations or orders. Clarke's hypothesis is, as Leibniz says, wholly without use or function, and requires a theory like that of Leibniz to account for the actually determinate forms of experience. In his last reply Clarke s.h.i.+fts his ground again, and says that s.p.a.ce and time are _effects_ of G.o.d's existence; "they are the necessary results of his existence." "His existence is the cause of s.p.a.ce and time." The death of Leibniz prevented any further reply. It is not hard to imagine, however, that in a general way his reply would have been to ask how s.p.a.ce and time are at once attributes essential and necessary to G.o.d, as const.i.tuting his immensity and eternity, and effects dependent upon his existence. To take this latter position, indeed, seems to abandon the position that they are absolute, and to admit that, like the rest of G.o.d's creation, they are relative and finite.