Freethought Archives > Baron d'Holbach > The System of Nature

MOTION is an effect by which a body either changes, or has a tendency to change, its position: that is to say, by which it successively corresponds with different parts of space, or changes its relative distance to other bodies. It is motion alone that establishes the relation between our senses and exterior or interior beings: it is only by motion that these beings are impressed upon us--that we know their existence--that we judge of their properties-- that we distinguish the one from the other--that we distribute them into classes.

The beings, the substances, or the various bodies of which Nature is the assemblage, are themselves effects of certain combinations or causes which become causes in their turn. A CAUSE is a being which puts another in motion, or which produces some change in it. The EFFECT is the change produced in one body, by the motion or presence of another.

Each being, by its essence, by its peculiar nature, has the faculty of producing, is capable of receiving, has the power of communicating, a variety of motion. Thus some beings are proper to strike our organs; these organs are competent to receiving the impression, are adequate to undergoing changes by their presence. Those which cannot act on any of our organs, either immediately and by themselves, or immediately by the intervention of other bodies, exist not for us; since they can neither move us, nor consequently furnish us with ideas: they can neither be known to us, nor of course be judged of by us. To know an object, is to have felt it; to feel it, it is requisite to have been moved by it. To see, is to have been moved, by something acting on the visual organs; to hear, is to have been struck, by something on our auditory nerves. In short, in whatever mode a body may act upon us, whatever impulse we may receive from it, we can have no other knowledge of it than by the change it produces in us.

Nature, as we have already said, is the assemblage of all the beings, consequently of all the motion of which we have a knowledge, as well as of many others of which we know nothing, because they have not yet become accessible to our senses. From the continual action and re-action of these beings, result a series of causes and effects; or a chain of motion guided by the constant and invariable laws peculiar to each being; which are necessary or inherent to its particular nature--which make it always act or move after a determinate manner. The different principles of this motion are unknown to us, because we are in many instances, if not in all, ignorant of what constitutes the essence of beings. The elements of bodies escape our senses; we know them only in the mass: we are neither acquainted with their intimate combination, nor the proportion of these combinations; from whence must necessarily result their mode of action, their impulse, or their different effects.

Our senses bring us generally acquainted with two sorts of motion in the beings that surround us: the one is the motion of the mass, by which an entire body is transferred from one place to another. Of the motion of this genus we are perfectly sensible.--Thus, we see a stone fall, a ball roll, an arm move, or change its position. The other is an internal or concealed motion, which always depends on the peculiar energies of a body: that is to say, on its essence, or the combination, the action, and re-action of the minute--of the insensible particles of matter, of which that body is composed. This motion we do not see; we know it only by the alteration or change, which after some time we discover in these bodies or mixtures. Of this genus is that concealed motion which fermentation produces in the particles that compose flour, which, however scattered, however separated, unite, and form that mass which we call BREAD. Such also is the imperceptible motion by which we see a plant or animal enlarge, strengthen, undergo changes, and acquire new qualities, without our eyes being competent to follow its progression, or to perceive the causes which have produced these effects. Such also is the internal motion that takes place in man, which is called his INTELLECTUAL FACULTIES, his THOUGHTS, his PASSIONS, his will. Of these we have no other mode of judging, than by their action; that is, by those sensible effects which either accompany or follow them. Thus, when we see a man run away, we judge him to be interiorly actuated by the passion of fear.

Motion, whether visible or concealed, is styled ACQUIRED, when it is impressed on one body by another; either by a cause to which we are a stranger, or by an exterior agent which our senses enable us to discover. Thus we call that acquired motion, which the wind gives to the sails of a ship. That motion which is excited in a body, that contains within itself the causes of those changes we see it undergo, is called SPONTANEOUS. Then it is said, this body acts or moves by its own peculiar energies. Of this kind is the motion of the man who walks, who talks, who thinks. Nevertheless, if we examine the matter a little closer, we shall be convinced, that, strictly speaking, there is no such thing as spontaneous motion in any of the various bodies of Nature; seeing they are perpetually acting one upon the other; that all their changes are to be attributed to the causes, either visible or concealed, by which they are moved. The will of man is secretly moved or determined by some exterior cause that produces a change in him: we believe he moves of himself, because we neither see the cause that determined him, the mode in which it acted, nor the organ that it put in motion.

That is called SIMPLE MOTION, which is excited in a body by a single cause. COMPOUND MOTION, that which is produced by two or more different causes; whether these causes are equal or unequal, conspiring differently, acting together or in succession, known or unknown.

Let the motion of beings be of whatsoever nature it may, it is always the necessary consequence of their essence, or of the properties which compose them, and of those causes of which they experience the action. Each being can only move and act after a particular manner; that is to say, conformably to those laws which result from its peculiar essence, its particular combination, its individual nature: in short, from its specific energies, and those of the bodies from which it receives an impulse. It is this that constitutes the invariable laws of motion: I say invariable, because they can never change, without producing confusion in the essence of things. It is thus that a heavy body must necessarily fall, if it meets with no obstacle sufficient to arrest its descent; that a sensible body must naturally seek pleasure, and avoid pain; that fire must necessarily burn, and diffuse light.

Each being, then, has laws of motion, that are adapted to itself, and constantly acts or moves according to these laws; at least when no superior cause interrupts its action. Thus, fire ceases to burn combustible matter, as soon as sufficient water is thrown into it, to arrest its progress. Thus, a sensible being ceases to seek pleasure, as soon as he fears that pain will be the result.

The communication of motion, or the medium of action, from one body to another, also follows certain and necessary laws; one being can only communicate motion to another, by the affinity, by the resemblance, by the conformity, by the analogy, or by the point of contact, which it has with that other being. Fire can only propagate when it finds matter analogous to itself: it extinguishes when it encounters bodies which it cannot embrace; that is to say, that do not bear towards it a certain degree of relation or affinity.

Every thing in the universe is in motion: the essence of matter is to act: if we consider its parts, attentively, we shall discover there is not a particle that enjoys absolute repose. Those which appear to us to be without motion, are, in fact, only in relative or apparent rest; they experience such an imperceptible motion, and expose it so little on their surfaces, that we cannot perceive the changes they undergo. All that appears to us to be at rest, does not, however, remain one instant in the same state. All beings are continually breeding, increasing, decreasing, or dispersing, with more or less dullness or rapidity. The insect called EPHEMERON, is produced and perishes in the same day; of consequence, it experiences the greatest changes of its being very rapidly, in our eyes. Those combinations which form the most solid bodies, which appear to enjoy the most perfect repose, are nevertheless decomposed, and dissolved in the course of time. The hardest stones, by degrees, give way to the contact of air. A mass of iron, which time, and the action of the atmosphere, has gnawed into rust, must have been in motion, from the moment of its formation, in the bowels of the earth, until the instant we behold it in this state of dissolution.

Natural philosophers, for the most part, seem not to have sufficiently reflected on what they call the nisus; that is to say, the incessant efforts one body is making on another, but which, notwithstanding appear, to our superficial observation, to enjoy the most perfect repose. A stone of five hundred weight seems to rest quiet on the earth, nevertheless, it never ceases for an instant, to press with force upon the earth, which resists or repulses it in its turn. Will the assertion be ventured, that the stone and earth do not act? Do they wish to be undeceived? They have nothing to do but interpose their hand betwixt the earth and the stone; it will then be discovered, that notwithstanding its seeming repose, the stone has power adequate to bruise it; because the hand has not energies sufficient, within itself, to resist effectually both the stone and earth.--Action cannot exist in bodies without re-action. A body that experiences an impulse, an attraction, or a pressure of any kind, if it resists, clearly demonstrates by such resistance that it re-acts; from whence it follows, there is a concealed force, called by these philosophers vis inertia, that displays itself against another force; and this clearly demonstrates, that this inert force is capable of both acting and re-acting. In short, it will be found, on close investigation, that those powers which are called dead, and those which are termed live or moving, are powers of the same kind; which only display themselves after a different manner. Permit us to go a greater distance yet. May we not say, that in those bodies, or masses, of which their whole become evident from appearances to us to be at rest, there is notwithstanding, a continual action, and counter-action, constant efforts, uninterrupted or communicated force, and continued opposition? In short, a nisus, by which the constituting portions of these bodies press one upon another, mutually resisting each other, acting and re-acting incessantly? that this reciprocity of action, this simultaneous re-action, keeps them united, causes their particles to form a mass, a body, and a combination, which, viewed in its whole, has the appearance of complete rest, notwithstanding no one of its particles really ceases to be in motion for a single instant? These collective masses appear to be at rest, simply by the equality of the motion--by the responsory impulse of the powers acting in them.

Thus it appears that bodies enjoying perfect repose, really receive, whether upon their surface, or in their interior, a continual communicated force, from those bodies by which they are either surrounded or penetrated, dilated or contracted, rarified or condensed: in fact, from those which compose them; whereby their particles are incessantly acting and re-acting, or in continual motion, the effects of which are displayed by extraordinary changes. Thus heat rarifies and dilates metals, which is evidence deducible that a bar of iron, from the change of the atmosphere alone, must be in continual motion; that there is not a single particle in it that can be said to enjoy rest even for a single moment. In those hard bodies, indeed, the particles of which are in actual contact, and which are closely united, how is it possible to conceive, that air, cold, or heat, can act upon one of these particles, even exteriorly, without the motion being communicated to those which are most intimate and minute in their union? Without motion, how should we be able to comprehend the manner in which our sense of smelling is affected, by emanations escaping from the most solid bodies, of which all the particles appear to be at perfect rest? How could we, even by the assistance of a telescope, see the most distant stars, if there was not a progressive motion of light from these stars to the retina of our eye?

Observation and reflection ought to convince us, that every thing in Nature is in continual motion-- that there is not a single part, however small, that enjoys repose--that Nature acts in all--that she would cease to be Nature if she did not act. Practical knowledge teaches us, that without unceasing motion, nothing could be preserved--nothing could be produced--nothing could act in this Nature. Thus the idea of Nature necessarily includes that of motion. But it will be asked, and not a little triumphantly, from whence did she derive her motion? Our reply is, we know not, neither do they--that we never shall, that they never will. It is a secret hidden from us, concealed from them, by the most impenetrable veil. We also reply, that it is fair to infer, unless they can logically prove to the contrary, that it is in herself, since she is the great whole, out of which nothing can exist. We say this motion is a manner of existence, that flows, necessarily, out of the nature of matter; that matter moves by its own peculiar energies; that its motion is to be attributed to the force which is inherent in itself; that the variety of motion, and the phenomena which result, proceed from the diversity of the properties--of the qualities--of the combinations, which are originally found in the primitive matter, of which Nature is the assemblage.

Natural philosophers, for the most part, have regarded as inanimate, or as deprived of the faculty of motion, those bodies which are only moved by the intervention of some agent or exterior cause; they have considered themselves justified in concluding, that the matter which forms these bodies is perfectly inert in its nature. They have not forsaken this error, although they must have observed, that whenever a body is left to itself, or disengaged from those obstructions which oppose themselves to its descent, it has a tendency to fall or to approach the centre of the earth, by a motion uniformly accelerated; they have rather chosen to suppose a visionary exterior cause, of which they themselves had but an imperfect idea, than admit that these bodies held their motion from their own peculiar nature.

These philosophers, also, notwithstanding they saw above them an infinite number of globes that moved with great rapidity round a common centre, still adhered to their favourite opinions; and never ceased to suppose some whimsical causes for these movements, until the immortal NEWTON clearly demonstrated that it was the effect of the gravitation of these celestial bodies towards each other. Experimental philosophers, however, and amongst them the great Newton himself, have held the cause of gravitation as inexplicable. Notwithstanding the great weight of this authority, it appears manifest that it may be deduced from the motion of matter, by which bodies are diversely determined. Gravitation is nothing more than a mode of moving--a tendency towards a centre: to speak strictly, all motion is relative gravitation; since that which falls relatively to us, rises, with relation to other bodies. From this it follows, that every motion in our microcosm is the effect of gravitation; seeing that there is not in the universe either top or bottom, nor any absolute centre. It should appear, that the weight of bodies depends on their configuration, as well external as internal, which gives them that form of action which is called gravitation. Thus, for instance, a piece of lead, spherically formed, falls quickly and direct: reduce this ball into very thin plates, it will be sustained in the air for a much longer time: apply to it the action of fire, this lead will rise in the atmosphere: here, then, the same metal, variously modified, has very different modes of action.

A very simple observation would have sufficed to make the philosophers, antecedent to Newton, feel the inadequateness of the causes they admitted to operate with such powerful effect. They had a sufficiency to convince themselves, in the collision of two bodies, which they could contemplate, and in the known laws of that motion, which these always communicate by reason of their greater or less compactness; from whence they ought to have inferred, that the density of subtle or ethereal matter, being considerably less than that of the planets, it could only communicate to them a very feeble motion, quite insufficient to produce that velocity of action, of which they could not possibly avoid being the witnesses.

If Nature had been viewed uninfluenced by prejudice, they must have been long since convinced that matter acts by its own peculiar activity; that it needs no exterior communicative force to set it in motion. They might have perceived that whenever mixed bodies were placed in a situation to act on each other, motion was instantly excited; and that these mixtures acted with a force capable of producing the most surprising results.

If particles of iron, sulphur, and water be mixed together, these bodies thus capacitated to act on each other, are heated by degrees, and ultimately produce a violent combustion. If flour be wetted with water, and the mixture closed up, it will be found, after some lapse of time, (by the aid of a microscope) to have produced organized beings that enjoy life, of which the water and the flour were believed incapable: it is thus that inanimate matter can pass into life, or animate matter, which is in itself only an assemblage of motion.

Reasoning from analogy, which the philosophers of the present day do not hold incompatible, the production of a man, independent of the ordinary means, would not be more astonishing than that of an insect with flour and water. Fermentation and putrid substances, evidently produce living animals. We have here the principle; with proper materials, principles can always be brought into action. That generation which is styled uncertain is only so for those who do not reflect, or who do not permit themselves, attentively, to observe the operations of Nature.

The generative of motion, and its development, as well as the energy of matter, may be seen everywhere; more particularly in those unitions in which fire, air, and water, find themselves combined. These elements, or rather these mixed bodies, are the most volatile, the most fugitive of beings; nevertheless in the hands of Nature, they are the essential agents employed to produce the most striking phenomena. To these we must ascribe the effects of thunder, the eruption of volcanoes, earthquakes, &c. Science offers to our consideration an agent of astonishing force, in gunpowder, the instant it comes in contact with fire. In short, the most terrible effects result from the combination of matter, which is generally believed to be dead and inert.

These facts prove, beyond a doubt, that motion is produced, is augmented, is accelerated in matter, without the help of any exterior agent: therefore it is reasonable to conclude that motion is the necessary consequence of immutable laws, resulting from the essence, from the properties existing in the different elements, and the various combinations of these elements. Are we not justified, then, in concluding, from these precedents, that there may be an infinity of other combinations, with which we are unacquainted, competent to produce a great variety of motion in matter, without being under the necessity of having recourse, for the explanation, to agents who are more difficult to comprehend than even the effects which are attributed to them?

Had man but paid proper attention to what passed under his review, he would not have sought out of Nature, a power distinguished from herself, to set her in action, and without which he believes she cannot move. If, indeed, by Nature is meant a heap of dead matter, destitute of peculiar qualities purely passive, we must unquestionably seek out of this Nature the principle of her motion. But if by Nature be understood, what it really is, a whole, of which the numerous parts are endowed with various properties, which oblige them to act according to these properties; which are in a perpetual ternateness of action and re-action; which press, which gravitate towards a common center, whilst others depart from and fly off towards the periphery, or circumference; which attract and repel; which by continual approximation and constant collision, produce and decompose all the bodies we behold; then, I say, there is no necessity to have recourse to supernatural powers, to account for the formation of things, and those extraordinary appearances which are the result of motion.

Those who admit a cause exterior to matter, are obliged to believe that this cause produced all the motion by which matter is agitated in giving it existence. This belief rests on another, namely, that matter could begin to exist; an hypothesis that, until this moment, has never been satisfactorily demonstrated. To produce from nothing, or the CREATION, is a term that cannot give us the least idea of the formation of the universe; it presents no sense, upon which the mind can rely. In fact, the human mind is not adequate to conceive a moment of non-existence, or when all shall have passed away; even admitting this to be a truth, it is no truth for us, because by the very nature of our organization, we cannot admit positions as facts, of which no evidence can be adduced that has relation to our senses; we may, indeed, consent to believe it, because others say it; but will any rational being be satisfied with such an admission? Can any moral good spring from such blind assurance? Is it consistent with sound doctrine, with philosophy, or with reason? Do we, in fact, pay any respect to the intellectual powers of another, when we say to him, "I will believe this, because in all the attempts you have ventured, for the purpose of proving what you say, you have entirely failed; and have been at last obliged to acknowledge you know nothing about the matter?" What moral reliance ought we to have on such people? Hypothesis may succeed hypothesis; system may destroy system: a new set of ideas may overturn the ideas of a former day. Other Gallileos may be condemned to death--other Newtons may arise--we may reason--argue--dispute--quarrel--punish and destroy: nay, we may even exterminate those who differ from us in opinion; but when we have done all this, we shall be obliged to fall back upon our original darkness--to confess, that that which has no relation with our senses, that which cannot manifest itself to us by some of the ordinary modes by which other things are manifested, has no existence for us--is not comprehensible by us--can never entirely remove our doubt--can never seize on our stedfast belief; seeing it is that of which we cannot form even a notion; in short, that it is that, which as long as we remain what we are, must be hidden from us by a veil, which no power, no faculty, no energy we possess, is able to remove. All who are not enslaved by prejudice agree to the truth of the position, that nothing can be made of nothing.

Many theologians have acknowledged Nature to be an active whole. Almost all the ancient philosophers were agreed to regard the world as eternal. OCELLUS LUCANUS, speaking of the universe, says, "it has always been, and it always will be." VATABLE and GROTIUS assure us, that to render the Hebrew phrase in the first chapter of GENESIS correctly, we must say, "when God made heaven and earth, matter was without form." If this be true, and every Hebraist can judge for himself, then the word which has been rendered created, means only to fashion, form, arrange. We know that the Greek words create and form, have always indicated the same thing. According to ST. JEROME, creare has the same meaning as condere, to found, to build. The Bible does not anywhere say in a clear manner, that the world was made of nothing. TERTULLIAN and the father PETAU both admit, that "this is a truth established more by reason than by authority." ST. JUSTIN seems to have contemplated matter as eternal, since he commends PLATO for having said, that "God, in the creation of the world, only gave impulse to matter, and fashioned it." BURNET and PYTHAGORAS were entirely of this opinion, and even our Church Service may be adduced in support; for although it admits by implication a beginning, it expressly denies an end: "As it was in the beginning, is now, and ever shall be, world without end." It is easy to perceive that that which cannot cease to exist, must have always been.

Motion becomes still more obscure, when creation, or the formation of matter, is attributed to a SPIRITUAL being; that is to say, to a being which has no analogy, no point of contact, with it--to a being which has neither extent or parts, and cannot, therefore, be susceptible of motion, as we understand the term; this being only the change of one body, relatively to another body, in which the body moved presents successively different parts to different points of space. Moreover, as all the world are nearly agreed that matter can never be totally annihilated, or cease to exist; by what reasoning, I would ask, do they comprehend--how understand--that that which cannot cease to be, could ever have had a beginning?

If, therefore, it be asked, whence came matter? it is very reasonable to say it has always existed. If it be inquired, whence proceeds the motion that agitates matter? the same reasoning furnishes the answer; namely, that as motion is coeval with matter, it must have existed from all eternity, seeing that motion is the necessary consequence of its existence--of its essence--of its primitive properties, such as its extent, its gravity, its impenetrability, its figure, &c. By virtue of these essential constituent properties, inherent in all matter, and without which it is impossible to form an idea of it, the various matter of which the universe is composed must from all eternity have pressed against, each other--have gravitated towards a center--have clashed--have come in contact--have been attracted--have been repelled--have been combined--have been separated: in short, must have acted and moved according to the essence and energy peculiar to each genus, and to each of its combinations.

Existence supposes properties in the thing that exists: whenever it has properties, its mode of action must necessarily flow from those properties which constitute, its mode of being. Thus, when a body is ponderous, it must fall; when it falls, it must come in collision with the bodies it meets in its descent; when it is dense, when it is solid, it must, by reason of this density, communicate motion to the bodies with which it clashes; when it has analogy, when it has affinity with these bodies, it must be attracted, must be united with them; when it has no point of analogy with them, it must be repulsed.

From which it may be fairly inferred, that in supposing, as we are under the necessity of doing, the existence of matter, we must suppose it to have some kind of properties; from which its motion, or modes of action, must necessarily flow. To form the universe, DESCARTES asked but matter and motion: a diversity of matter sufficed for him; variety of motion was the consequence of its existence, of its essence, of its properties: its different modes of action would be the necessary consequence of its different modes of being. Matter without properties would be a mere nothing; therefore, as soon as matter exists, it must act; as soon as it is various, it must act variously; if it cannot commence to exist, it must have existed from all eternity; if it has always existed, it can never cease to be: if it can never cease to be, it can never cease to act by its own energy. Motion is a manner of being, which matter derives from its peculiar existence.

The existence, then, of matter is a fact: the existence of motion is another fact. Our visual organs point out to us matter with different essences, forming a variety of combinations, endowed with various properties that discriminate them. Indeed, it is a palpable error to believe that matter is a homogeneous body, of which the parts differ from each other only by their various modifications. Among the individuals of the same species that come under our notice, no two resemble exactly; and it is therefore evident that the difference of situation alone will, necessarily, carry a diversity more or less sensible, not only in the modifications, but also in the essence, in the properties, in the entire system of beings. This truth was well understood by the profound and subtle LEIBNITZ.

If this principle be properly digested, and experience seems always to produce evidence of its truth, we must be convinced that the matter or primitive elements which enter into the composition of bodies, are not of the same nature, and consequently, can neither have the same properties, nor the same modifications; and if so, they cannot have the same mode of moving and acting. Their activity or motion, already different, can be diversified to infinity, augmented or diminished, accelerated or retarded, according to the combinations, the proportions, the pressure, the density, the volume of the matter, that enters their composition. The endless variety to be produced, will need no further illustration than the commonest book of arithmetic furnishes us, where it will be found, that to ring all the changes that can be produced on twelve bells only, would occupy a space of more than ninety-one years. The element of fire is visibly more active and more inconstant than that of earth. This is more solid and ponderous than fire, air, or water. According to the quantity of these elements, which enter the composition of bodies, these must act diversely, and their motion must in some measure partake the motion peculiar to each of their constituent parts. Elementary fire appears to be in Nature the principle of activity; it may be compared to a fruitful leaven, that puts the mass into fermentation and gives it life. Earth appears to be the principle of solidity in bodies, from its impenetrability, and by the firm coherence of its parts. Water is a medium, to facilitate the combination of bodies, into which it enters itself, as a constituent part. Air is a fluid whose business it seems to be, to furnish the other elements with the space requisite to expand, to exercise their motion, and which is, moreover, found proper to combine with them. These elements, which our senses never discover in a pure state--which are continually and reciprocally set in motion by each other--which are always acting and re-acting, combining and separating, attracting and repelling--are sufficient to explain to us the formation of all the beings we behold. Their motion is uninterruptedly and reciprocally produced from each other; they are alternately causes and effects. Thus, they form a vast circle of generation and destruction--of combination and decomposition, which, it is quite reasonable to suppose, could never have had a beginning, and which, consequently can never have an end. In short, Nature is but an immense chain of causes and effects, which unceasingly flow from each other. The motion of particular beings depends on the general motion, which is itself maintained by individual motion. This is strengthened or weakened, accelerated or retarded, simplified or complicated, procreated or destroyed, by a variety of combinations and circumstances, which every moment change the directions, the tendency, the modes of existing, and of acting, of the different beings that receive its impulse.

If it were true, as has been asserted by some philosophers, that every thing has a tendency to form one unique or single mass, and in that unique mass the instant should arrive when all was in nisus, all would eternally remain in this state; to all eternity there would be no more than one Being and one effort: this would be eternal and universal death.

If we desire to go beyond this, to find the principle of action in matter, to trace the origin of things, it is for ever to fall back upon difficulties; it is absolutely to abridge the evidence of our senses; by which only we can understand, by which alone we can judge of the causes acting upon them, or the impulse by which they are set in action.

Let us, therefore, content ourselves with saying WHAT is supported by our experience, and by all the evidence we are capable of understanding; against the truth of which not a shadow of proof, such as our reason can admit, has ever been adduced--which has been maintained by philosophers in every age--which theologians themselves have not denied, but which many of them have upheld; namely, that matter always existed; that it moves by virtue of its essence; that all the phenomena of Nature is ascribable to the diversified motion of the variety of matter she contains; and which, like the phoenix, is continually regenerating out of its own ashes.