The System of Nature, or, the Laws of the Moral and Physical World. Volume 1 · Paul Henri Thiry Holbach
CHAP. VIII.
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 PASSIONS 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 analogy 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 passions 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 assemblage 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 compass 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 be said to flow consecutively, that all its operations, all its faculties, prove that it is itself _material_.
Ideas discussed in this chapter
Text from Project Gutenberg, public domain in the United States.