The System of Nature or the Laws of the Moral and Physical World Volume I Part 5

If man wishes to form to himself clear, perspicuous ideas of his soul, let him throw himself back on his experience--let him renounce his prejudices--let him avoid theological conjecture--let him tear the bandages which he has been taught to think necessary, but with which he has been blind-folded, only to confound his reason. If it be wished to draw man to virtue, let the natural philosopher, let the anatomist, let the physician, unite their experience; let them compare their observations, in order to show what ought to be thought of a substance, so disguised, so hidden by absurdities, as not easily to be known. Their discoveries may perhaps teach moralists the true motive-power that ought to influence the actions of man--legislators, the true motives that should actuate him, that should excite him to labour to the welfare of society--sovereigns, the means of rendering their subjects truly happy; of giving solidity to the power of the nations committed to their charge. Physical souls have physical wants, and demand physical happiness. These are real, are preferable objects, to that variety of fanciful chimeras, each in its turn giving place to the other, with which the mind of man has been fed during so many ages. Let us, then, labour to perfect the morality of man; let us make it agreeable to him; let us excite in him an ardent thirst for its purity: we shall presently see his morals become better, himself become happier; his soul become calm and serene; his will determined to virtue, by the natural, by the palpable motives held out to him. By the diligence, by the care which legislators shall bestow on natural philosophy, they will form citizens of sound understandings; robust and well const.i.tuted; who, finding themselves happy, will be themselves accessary to that useful impulse so necessary for their soul. When the body is suffering, when nations are unhappy, the soul cannot be in a proper state. _Mens sana in corpore sano_, a sound mind in a sound body, will be always able to make a good citizen.

The more man reflects, the more he will be convinced that the soul, very far from being distinguished from the body, is only the body itself, considered relatively to some of its functions, or to some of the modes of existing or acting, of which it is susceptible whilst it enjoys life.

Thus, the soul is man, considered relatively to the faculty he has of feeling, of thinking, of acting in a mode resulting from his peculiar nature; that is to say, from his properties, from his particular organization: from the modifications, whether durable or transitory, which the beings who act upon him cause his machine to undergo.

Those who have distinguished the soul from the body, appear only to have distinguished their brain from themselves. Indeed, the brain is the common center, where all the nerves, distributed through every part of the body, meet and blend themselves: it is by the aid of this interior organ that all those operations are performed which are attributed to the soul: it is the impulse, or the motion, communicated to the nerve, which modifies the brain: in consequence, it re-acts, or gives play to the bodily organs; or rather it acts upon itself, and becomes capable of producing within itself a great variety of motion, which has been designated _intellectual faculties_.

From this it may be seen that some philosophers have been desirous to make a spiritual substance of the brain. It is evidently nothing but ignorance that has given birth to and accredited this system, which embraces so little, either of the natural or the rational. It is from not having studied himself, that man has supposed he was compounded with an agent, essentially different from his body: in examining this body, he will find that it is quite useless to recur to hypothesis for the explanation of the various phenomena it presents to his contemplation; that hypothesis can do nothing more than lead him out of the right road to the information after which he seeks. What obscures this question, arises from this, that man cannot see himself: indeed, for this purpose, that would be requisite which is impossible; namely, that he could he at one and the same moment both within and without himself: he may be compared to an Eolian harp, that issues sounds of itself, and should demand what it is that causes it to give them forth? It does not perceive that the sensitive quality of its chords causes the air to brace them; that being so braced, it is rendered sonorous by every gust of wind with which it happens to come in contact.

When a theologian, obstinately bent on admitting into man two substances essentially different, is asked why he multiplies beings without necessity? he will reply, because _"thought cannot be a property of matter."_ If, then, it be enquired of him, _cannot G.o.d give to matter the faculty of thought?_ he will answer, _"no! seeing that G.o.d cannot do impossible things!"_ According to his principles, it is as impossible that spirit or thought can produce matter, as it is impossible that matter can produce spirit or thought: it might, therefore, be concluded against him, that the world was not made by a spirit, any more than a spirit was made by the world. But in this case, does not the theologian, according to his own a.s.sertion, acknowledge himself to be the true atheist? Does he not, in fact, circ.u.mscribe the attributes of the Deity, and deny his power, to suit his own purpose? Yet these men demand implicit belief in doctrines, which they are obliged to maintain by the most contradictory a.s.sertions.

The more experience we collect, the more we shall be convinced that the word _spirit_, in its present received usage, conveys no one sense that is tangible, either to ourselves or to those that invented it; consequently cannot be of the least use, either in physics or morals.

What modern metaphysicians believe and understand by the word, is nothing more than an _occult_ power, imagined to explain _occult_ qualities and actions, but which, in fact, explains nothing. Savage nations admit of spirits, to account to themselves for those effects, which to them appear marvellous, as long as their ignorance knows not the cause to which they ought to be attributed. In attributing to spirits the phenomena of Nature, as well as those of the human body, do we, in fact, do any thing more than reason like savages? Man has filled Nature with spirits, because he has almost always been ignorant of the true causes of those effects by which he was astonished. Not being acquainted with the powers of Nature, he has supposed her to be animated by a _great spirit_: not understanding the energy of the human frame, he has in like manner conjectured it to be animated by a _minor spirit_: from this it would appear, that whenever he wished to indicate the unknown cause of a phenomena, he knew not how to explain in a natural manner, he had recourse to the word _spirit_. In short, _spirit_ was a term by which he solved all his doubts, and cleared up his ignorance to himself. It was according to these principles that when the AMERICANS first beheld the terrible effects of gunpowder, they ascribed the cause to wrathful spirits, to their enraged divinities: it was by adopting these principles, that our ancestors believed in a plurality of G.o.ds, in ghosts, in genii, &c. Pursuing the same track, we ought to attribute to spirits gravitation, electricity, magnetism, &c. &c. It is somewhat singular, that priests have in all ages so strenuously upheld those systems which time has exploded; that they have appeared to be either the most crafty or the most ignorant of men. Where are now the priests of Apollo, of Juno, of the Sun, and a thousand others? Yet these are the men, who in all times have persecuted those who have been the first to give natural explanations of the phenomena of Nature, as witness ANAXAGORAS, ARISTOTLE, GALLILEO, DESCARTES, &c. &c.

CHAP. VIII.

_The Intellectual Faculties derived from the Faculty of Feeling_.

To convince ourselves that the faculties called _intellectual_, are only certain modes of existence, or determinate manners of acting, which result from the peculiar organization of the body, we have only to a.n.a.lyze them; we shall then see that all the operations which are attributed to the soul, are nothing more than certain modifications of the body; of which a substance that is without extent, that has no parts, that is immaterial, is not susceptible.

The first faculty we behold in the living man, and that from which all his others flow, is _feeling_: however inexplicable this faculty may appear, on a first view, if it be examined closely, it will be found to be a consequence of the essence, or a result of the properties of organized beings; the same as _gravity, magnetism, elasticity, electricity_, &c. result from the essence or nature of some others. We shall also find these last phenomena are not less inexplicable than that of feeling. Nevertheless, if we wish to define to ourselves a clear and precise idea of it, we shall find that feeling is a particular manner of being moved--a mode of receiving an impulse peculiar to certain organs of animated bodies, which is occasioned by the presence of a material object that acts upon these organs, and transmit the impulse or shock to the brain.

Man only feels by the aid of nerves dispersed through his body; which is itself, to speak correctly, nothing more than a great nerve; or may be said to resemble a large tree, of which the branches experience the action of the root, communicated through the trunk. In man the nerves unite and lose themselves in the brain; that intestine is the true seat of feeling: like the spider in the centre of his web, it is quickly warned of all the changes that happen to the body, even at the extremities to which it sends its filaments and branches. Experience enables us to ascertain, that man ceases to feel in those parts of his body of which the communication with the brain is intercepted; he feels very little, or not at all, whenever this organ is itself deranged or affected in too lively a manner. A proof of this is afforded in the transactions of the Royal Academy of Sciences at Paris: they inform us of a man who had his scull taken off, in the room of which his brain was recovered with skin; in proportion as a pressure was made by the hand on his brain, the man fell into a kind of insensibility, which deprived him of all feeling. BARTOLIN says, the brain of a man is twice as big as that of an ox. This observation had been already made by ARISTOTLE. In the dead body of an idiot dissected by WILLIS, the brain was found smaller than ordinary: he says the greatest difference he found between the parts of the body of this idiot, and those of wiser men, was, that the plexus of the intercostal nerves, which is the mediator between the brain and the heart, was extremely small, accompanied by a less number of nerves than usual. According to WILLIS, the ape is, of all animals, that which has the largest brain, relatively to his size: he is also, after man, that which has the most intelligence: this is further confirmed, by the name he bears in the soil, to which he is indigenous, which is _ourang outang_, or the man beast. There is, therefore, every reason to believe that it is entirely in the brain, that consists the difference, that is found not only between man and beasts, but also between the man of wit, and the fool: between the thinking man, and he who is ignorant; between the man of sound understanding, and the madman: a mult.i.tude of experience, serves to prove, that those persons who are most accustomed to use their intellectual faculties, have their brain more extended than others: the same has been remarked of watermen, that they have arms much longer than other men.

However this may be, the sensibility of the brain, and all its parts, is a fact: if it be asked, whence comes this property? We shall reply, it is the result of an arrangement, of a combination, peculiar to the animal: it is thus that milk, bread, wine, change themselves in the substance of man, who is a sensible being: this insensible matter becomes sensible, in combining itself with a sensible whole. Some philosophers think that sensibility is a universal quality of matter: in this case, it would be useless to seek from whence this property is derived, as we know it by its effects. If this hypothesis be admitted, in like manner as two kinds of motion are distinguished in Nature, the one called _live_ force, the other _dead_, or _inert_ force, two sorts of sensibility will be distinguished, the one active or alive, the other inert or dead. Then to animalize a substance, is only to destroy the obstacles that prevent its being active or sensible. In fact, sensibility is either a quality which communicates itself like motion, and which is acquired by combination; or this sensibility is a property inherent in all matter: in both, or either case, an unextended being, without parts, such as the human soul is said to be, can neither be the cause of it nor submitted to its operation; but we may fairly conclude, that all the parts of Nature enjoy the capability to arrive at animation; the obstacle is only in the state, not in the quality. Life is the perfection of Nature: she has no parts which do not tend to it-- which do not attain it by the same means. Life in an insect, a dog, a man, has no other difference, than that this act is more perfect, relatively to ourselves in proportion to the structure of the organs: if, therefore, it be asked, what is requisite to animate a body? we reply, it needs no foreign aid; it is sufficient that the power of Nature be joined to its organization.

The conformation, the arrangement, the texture, the delicacy of the organs, as well exterior as interior, which compose men and animals, render their parts extremely mobile, or make their machine susceptible of being moved with great facility. In a body, which is only a heap of fibres, a ma.s.s of nerves, contiguous one to the other, united in a common center, always ready to act; in a whole, composed of fluids and solids, of which the parts are in equilibrium, the smallest touching each other, are active in their motion, communicating reciprocally, alternately and in succession, the impression, oscillations, and shocks they receive; in such a composition, it is not surprising that the slightest impulse propagates itself with celerity; that the shocks excited in its remotest parts, make themselves quickly felt in the brain, whose delicate texture renders it susceptible of being itself very easily modified. Air, fire, water, agents the most inconstant, possessing the most rapid motion, circulate continually in the fibres, incessantly penetrate the nerves: without doubt these contribute to that incredible celerity with which the brain is acquainted with what pa.s.ses at the extremities of the body.

Notwithstanding the great mobility with which man's organization renders him susceptible, although exterior as well as interior causes are continually acting upon him, he does not always feel in a distinct, in a decided manner, the impulse given to his senses: indeed, he does not feel it, until it has produced some change, or given some shock to his brain. Thus, although completely environed by air, he does not feel its action, until it is so modified, as to strike with a sufficient degree of force on his organs; to penetrate his skin, through which his brain is warned of its presence. Thus, during a profound and tranquil sleep, undisturbed by any dream, man ceases to feel. In short, notwithstanding the continued motion that agitates his frame, man does not appear to feel, when this motion acts in a convenient order; he does not perceive a state of health, but he discovers a state of grief or sickness; because, in the first, his brain does not receive too lively an impulse, whilst in the others, his nerves are contracted, shocked, and agitated, with violent, with disorderly motion: these communicating with his brain, give notice that some cause acts strongly upon them--impels them in a manner that bears no a.n.a.logy with their natural habit: this const.i.tutes, in him, that peculiar mode of existing which he calls _grief_.

On the other hand, it sometimes happens that exterior objects produce very considerable changes on his body, without his perceiving them at the moment. Often, in the heat of battle, the soldier perceives not that he is dangerously wounded, because, at the time, the rapidity, the multiplicity of impetuous motion that a.s.sails his brain, does not permit him to distinguish the particular change a part of his body has undergone by the wound. In short, when a great number of causes are simultaneously acting on him with too much vivacity, he sinks under their acc.u.mulated pressure,--he swoons--he loses his senses--he is deprived of feeling.

In general, feeling only obtains, when the brain can distinguish distinctly, the impressions made on the organs with which it has communication; it is the distinct shock, the decided modification man undergoes, that const.i.tutes _conscience_. Doctor Clarke, says to this effect: "Conscience is the act of reflecting, by means of which I know that I think, and that my thoughts, or my actions belong to me, and not to another." From this it will appear, that _feeling_ is a mode of being, a marked change, produced on our brain, occasioned by the impulse communicated to our organs, whether by interior or exterior agents, by which it is modified either in a durable or transient manner: it is not always requisite that man's organs should be moved by an exterior object, to enable him to feel that he should be conscious of the changes effected in him: he can feel them within himself by means of an interior impulse; his brain is then modified, or rather he renews within himself the anterior modifications. We are not to be astonished that the brain should be necessarily warned of the shocks, of the impediments, of the changes that may happen to so complicated a machine as the human body, in which, notwithstanding all the parts are contiguous to the brain, and concentrate themselves in this brain, and are by their essence in a continual state of action and re-action.

When a man experiences the pains of the gout, he is conscious of them; in other words, he feels interiorly, that it has produced very marked, very distinct changes in him, without his perceiving, that he has received an impulse from any exterior cause; nevertheless, if he will recur to the true source of these changes, he will find that they have been wholly produced by exterior agents: they have been the consequence, either of his temperament; of the organization received from his parents; of the aliments with which his frame has been nourished; besides a thousand trivial, inappreciable causes, which congregating themselves by degrees produce in him the gouty humour; the effect of which is to make him feel in an acute and very lively manner. The pain of the gout engenders in his brain an idea, so modifies it that it acquires the faculty of representing to itself, of reiterating as it were, this pain when even he shall be no longer tormented with the gout: his brain, by a series of motion interiorly excited, is again placed in a state a.n.a.logous to that in which it was when he really experienced this pain: but if he had never felt it, he would never have been in a capacity to form to himself any just idea of its excruciating torments.

The visible organs of man's body, by the intervention of which his brain is modified, take the name of _senses_. The various modifications which his brain receives by the aid of these senses, a.s.sumes a variety of names. _Sensation_, _perception_, and _idea_, are terms that designate nothing more than the changes produced in this interior organ, in consequence of impressions made on the exterior organs by bodies acting on them: these changes considered by themselves, are called _sensations_; they adopt the term _perception_ when the brain is warned of their presence; _ideas_ is that state of them in which the brain is able to ascribe them to the objects by which they have been produced.

Every _sensation_, then, is nothing more than the shock given to the organs, every _perception_ is this shock propagated to the brain; every _idea_ is the image of the object to which the sensation and the perception is to be ascribed. From whence it will be seen, that if the senses be not moved, there can neither be sensations, perceptions, nor ideas: this will be proved to those, who can yet permit themselves to doubt so demonstrable and striking a truth.

It is the extreme mobility of which man is capable, owing to his peculiar organization, that distinguishes him from other beings that are called insensible or inanimate; the different degrees of this mobility, of which the individuals of his species are susceptible, discriminate them from each other; make that incredible variety, that infinity of difference which is to be found, as well in their corporeal faculties, as in those which are mental or intellectual. From this mobility, more or less remarkable in each human being, results wit, sensibility, imagination, taste, &c.: for the present, however, let us follow the operation of the senses; let us examine in what manner they are acted upon, and are modified by exterior objects:--we will afterwards scrutinize the re-action of the interior organ or brain.

The eyes are very delicate, very movable organs, by means of which the sensation of light or colour is experienced: these give to the brain a distinct perception, in consequence of which, man forms an idea, generated by the action of luminous or coloured bodies: as soon as the eyelids are opened, the retina is affected in a peculiar manner; the fluid, the fibres, the nerves, of which they are composed, are excited by shocks which they communicate to the brain; to which they delineate the images of the bodies from which they have received the impulse; by this means, an idea is acquired of the colour, the size, the form, the distance of these bodies: it is thus that may he explained the mechanism of _sight_.

The mobility and the elasticity of which the skin is rendered susceptible, by the fibres and nerves which form its texture, accounts for the rapidity with which this envelope to the human body is affected when applied to any other body; by their agency, the brain has notice of its presence, of its extent, of its roughness, of its smoothness, of its surface, of its pressure of its ponderosity, &c. Qualities from which the brain derives distinct perceptions, which breed in it a diversity of ideas; it is this that const.i.tutes the _touch_ or _feeling_.

The delicacy of the membrane by which the interior of the nostrils is covered, renders them easily susceptible of irritation, even by the invisible and impalpable corpuscles that emanate from odorous bodies: by these means sensations are excited, the brain has perceptions, and generates ideas: it is this that forms the sense of _smelling_.

The mouth, filled with nervous, sensible, movable, irritable glands, saturated with juices suitable to the dissolution of saline substances, is affected in a very lively manner by the aliments which pa.s.s through it for the nourishment of the body; these glands transmit to the brain the impressions received: perceptions are of consequence; ideas follow: it is from this mechanism that results _taste_.

The ear, whose conformation fits it to receive the various impulses of air, diversely modified, communicates to the brain the shocks or sensations; these breed the perception of sound, and generate the idea of sonorous bodies: it is this that const.i.tutes _hearing_.

Such are the only means by which man receives sensations, perceptions, and ideas. These successive modifications of his brain are effects produced by objects that give impulse to his senses; they become themselves causes, producing in his soul new modifications, which are denominated _thought, reflection, memory, imagination, judgment, will, action_; the basis, however, of all these is _sensation_.

To form a precise notion of _thought_, it will be requisite to examine, step by step, what pa.s.ses in man during the presence of any object whatever. Suppose for a moment this object to be a peach: this fruit makes, at the first view, two different impressions on his eyes; that is to say, it produces two modifications, which are transmitted to the brain, which on this occasion experiences two new perceptions, or has two new ideas or modes of existence, designated by the terms _colour_ and _rotundity_; in consequence, he has an idea of a body possessing roundness and colour: if he places his hand on this fruit, the organ of feeling having been set in action, his hand experiences three new impressions, which are called _softness, coolness, weight_, from whence result three new perceptions in the brain, he has consequently three new ideas: if he approximates this peach to his nose, the organ of _smelling_ receives an impulse, which, communicated to the brain, a new perception arises, by which he acquires a new idea, called _odour_: if he carries this fruit to his mouth, the organ of taste becomes affected in a very lively manner: this impulse communicated to the brain, is followed by a perception that generates in him the idea of _flavour_. In re-uniting all these impressions, or these various modifications of his organs, which it have been consequently transmitted to his brain; that is to say, in combining the different sensations, perceptions, and ideas, that result from the impulse he has received, he has an idea of a whole, which he designates by the name of a peach, with which he can then occupy his thoughts.

From this it is sufficiently proved that thought has a commencement, a duration, an end; or rather a generation, a succession, a dissolution, like all the other modifications of matter; like them, thought is excited, is determined, is increased, is divided, is compounded, is simplified, &c. If, therefore, the soul, or the principle that thinks, be indivisible; how does it happen, that this soul has the faculty of memory, or of forgetfulness; is capacitated to think successively, to divide, to abstract, to combine, to extend its ideas, to retain them, or to lose them? How can it cease to think? If forms appear divisible in matter, it is only in considering them by abstraction, after the method, of geometricians; but this divisibility of form exists not in Nature, in which there is neither a point, an atom, nor form perfectly regular; it must therefore be concluded, that the forms of matter are not less indivisible than thought.

What has been said is sufficient to show the generation of sensations, of perceptions, of ideas, with their a.s.sociation, or connection in the brain: it will be seen that these various modifications are nothing more than the consequence of successive impulses, which the exterior organs transmit to the interior organ, which enjoys the faculty of thought, that is to say, to feel in itself the different modifications it has received, or to perceive the various ideas which it has generated; to combine them, to separate them, to extend them, to abridge them, to compare them, to renew them, &c. From whence it will be seen, that thought is nothing more than the perception of certain modifications, which the brain either gives to itself, or has received from exterior objects.

Indeed, not only the interior organ perceives the modifications it receives from without, but again it has the faculty of modifying itself; of considering the changes which take place in it, the motion by which it is agitated in its peculiar operations, from which it imbibes new perceptions and new ideas. It is the exercise of this power to fall back upon itself, that is called _reflection_.

From this it will appear, that for man to think and to reflect, is to feel, or perceive within himself the impressions, the sensations, the ideas, which have been furnished to his brain by those objects which give impulse to his senses, with the various changes which his brain produced on itself in consequence.

_Memory_ is the faculty which the brain has of renewing in itself the modifications it has received, or rather, to restore itself to a state similar to that in which it has been placed by the sensations, the perceptions, the ideas, produced by exterior objects, in the exact order it received them, without any new action on the part of these objects, or even when these objects are absent; the brain perceives that these modifications a.s.similate with those it formerly experienced in the presence of the objects to which it relates, or attributes them. Memory is faithful, when these modifications are precisely the same; it is treacherous, when they differ from those which the organs have exteriorly experienced.

_Imagination_ in man is only the faculty which the brain has of modifying itself, or of forming to itself new perceptions, upon the model of those which it has anteriorly received through the action of exterior objects on the senses. The brain, then, does nothing more than combine ideas which it has already formed, which it recalls to itself, from which it forms a whole, or a collection of modifications, which it has not received, which exists no-where but in itself, although the individual ideas, or the parts of which this ideal whole is composed, have been previously communicated to it, in consequence of the impulse given to the senses by exterior objects: it is thus man forms to himself the idea of _centaurs_, or a being composed of a man and a horse, of _hyppogriffs_, or a being composed of a horse with wings and a griffin, besides a thousand other objects, equally ridiculous. By memory, the brain renews in itself the sensations, the perceptions, and the ideas which it has received or generated; represents to itself the objects which have actually moved its organs. By imagination it combines them variously: forms objects in their place which have not moved its organs, although it is perfectly acquainted with the elements or ideas of which it composes them. It is thus that man, by combining a great number of ideas borrowed from himself, such as justice, wisdom, goodness, intelligence, &c. by the aid of imagination, has formed various ideal beings, or imaginary wholes, which he has called JUPITER, JUNO, BRAMAH, SATURN, &c.

_Judgment_ is the faculty which the brain possesses of comparing with each other the modifications it receives, the ideas it engenders, or which it has the power of awakening within itself, to the end that it may discover their relations, or their effects.

_Will_ is a modification of the brain, by which it is disposed to action, that is to say, to give such an impulse to the organs of the body, as can induce to act in a manner, that will procure for itself what is requisite to modify it in a mode a.n.a.logous to its own existence, or to enable it to avoid that by which it can be injured. To _will_ is to be disposed to _action_. The exterior objects, or the interior ideas, which give birth to this disposition are called _motives_, because they are the springs or movements which determine it to act, that is to say, which give play to the organs of the body. Thus, _voluntary actions_ are the motion of the body, determined by the modification of the brain.

Fruit hanging on a tree, through the agency of the visual organs, modifies the brain in such a manner as to dispose the arm to stretch itself forth to cull it; again, it modifies it in another manner, by which it excites the hand to carry it to the mouth.

All the modifications which the interior organ or the brain receives, all the sensations, all the perceptions, all the ideas that are generated by the objects which give impulse to the senses, or which it renews within itself by its own peculiar faculties, are either favourable or prejudicial to man's mode of existence, whether that be transitory or habitual: they dispose the interior organ to action, which it exercises by reason of its own peculiar energy: this action is not, however, the same in all the individuals of the human species, depending much on their respective temperaments. From hence the Pa.s.sIONS have their birth: these are more or less violent; they are, however, nothing more than the motion of the will, determined by the objects which give it activity; consequently composed of the a.n.a.logy or of the discordance which is found between these objects, man's peculiar mode of existence, and the force of his temperament. From this it results, that the pa.s.sions are modes of existence or modifications of the brain; which either attract or repel those objects by which man is surrounded; that consequently they are submitted in their action to the physical laws of attraction and repulsion.

The faculty of perceiving or of being modified, as well by itself as exterior objects which the brain enjoys is sometimes designated by the term _understanding_. To the a.s.semblage of the various faculties of which this interior organ is susceptible, is applied the name of _intelligence_. To a determined mode in which the brain exercises the faculties peculiar to itself, is given the appellation of _reason_. The dispositions or the modifications of the brain, some of them constant, others transitory, which give impulse to the beings of the human species, causing them to act, are styled _wit, wisdom, goodness, prudence, virtue, &c_.

In short, as there will be an opportunity presently to prove, all the intellectual faculties--that is to say, all the modes of action attributed to the soul, may be reduced to the modifications, to the qualities, to the modes of existence, to the changes produced by the motion of the brain; which is visibly in man the seat of feeling, the principle of all his actions. These modifications are to be attributed to the objects that strike on his senses; of which the impression is transmitted to the brain, or rather to the ideas, which the perceptions caused by the action of these objects on his senses have there generated, and which it has the faculty to re-produce. This brain moves itself in its turn, re-acts upon itself, gives play to the organs, which concentrate themselves in it, or which are rather nothing more than an extension of its own peculiar substance. It is thus the concealed motion of the interior organ, renders itself sensible by outward and visible signs. The brain, affected by a modification which is called FEAR, diffuses a paleness over the countenance, excites a tremulous motion in the limbs called trembling. The brain, affected by a sensation of GRIEF, causes tears to flow from the eyes, even without being moved by any exterior object; an idea which it retraces with great strength, suffices to give it very little modifications, which visibly have an influence on the whole frame.

In all this, nothing more is to be perceived than the same substance which acts diversely on the various parts of the body. If it be objected that this mechanism does not sufficiently explain the principles of the motion or the faculties of the soul; we reply, that it is in the same situation as all the other bodies of Nature, in which the most simple motion, the most ordinary phenomena, the most common modes of action are inexplicable mysteries, of which we shall never be able to fathom the first principles. Indeed, how can we flatter ourselves we shall ever be enabled to compa.s.s the true principle of that gravity by which a stone falls? Are we acquainted with the mechanism which produces attraction in some substances, repulsion in others? Are we in a condition to explain the communication of motion from one body to another? But it may be fairly asked,--Are the difficulties that occur, when attempting to explain the manner in which the soul acts, removed by making it a _spiritual being_, a substance of which we have not, nor cannot form one idea, which consequently must bewilder all the notions we are capable of forming to ourselves of this being? Let us then be contented to know that the soul moves itself, modifies itself, in consequence of material causes, which act upon it which give it activity: from whence the conclusion may he said to flow consecutively, that all its operations, all its faculties, prove that it is itself _material_.

CHAP. IX.

_The Diversity of the Intellectual Faculties: they depend on Physical Causes, as do their Moral Qualities.--The Natural Principles of Society.--Morals.--Politics_.

Nature is under the necessity of diversifying all her works. Elementary matter, different in its essence, must necessarily form different beings, various in their combinations, in their properties, in their modes of action, in their manner of existence. There is not, neither can there be, two beings, two combinations, which are mathematically and rigorously the same; because the place, the circ.u.mstances, the relations; the proportions, the modifications, never being exactly alike, the beings that result can never bear a perfect resemblance to each other: their modes of action must of necessity vary in something, even when we believe we find between them the greatest conformity.

In consequence of this principle, which every thing we see conspires to prove to be a truth, there are not two individuals of the human species who have precisely the same traits--who think exactly in the same manner--who view things under the same identical point of sight--who have decidedly the same ideas; consequently no two of them have uniformly the same system of conduct. The visible organs of man, as well as his concealed organs, have indeed some a.n.a.logy, some common points of resemblance, some general conformity; which makes them appear, when viewed in the gross, to be affected in the same manner by certain causes: but the difference is infinite in the detail. The human soul may be compared to those instruments, of which the chords, already diversified in themselves, by the manner in which they have been spun, are also strung upon different notes: struck by the same impulse, each chord gives forth the sound that is peculiar to itself; that is to say, that which depends on its texture, its tension, its volume, on the momentary state in which it is placed by the circ.u.mambient air. It is this that produces the diversified spectacle, the varied scene, which the moral world offers to our view: it is from this that results the striking contrariety that is to be found in the minds, in the faculties, in the pa.s.sions, in the energies, in the taste, in the imagination, in the ideas, in the opinions of man. This diversity is as great as that of his physical powers: like them it depends on his temperament, which is as much varied as his physiognomy. This variety gives birth to that continual series of action and reaction, which const.i.tutes the life of the moral world: from this discordance results the harmony which at once maintains and preserves the human race.