Department of History
University of California, Irvine
 Instructor:    Dr. Barbara J. Becker


Week 5.  Mechanism

excerpts from
Man a Machine (1748)
by Julien de la Mettrie (1709-1751)

Man is so complicated a machine that it is impossible to get a clear idea of the machine beforehand, and hence impossible to define it.  For this reason, all the investigations have been vain, which the greatest philosophers have made a priori....  Thus it is only a posteriori or by trying to disentangle the soul from the organs of the body, so to speak, that one can reach the highest probability concerning man's own nature, even though one cannot discover with certainty what his nature is....

The human body is a machine which winds its own springs.  It is the living image of perpetual movement.  Nourishment keeps up the movements which fever excites.  Without food, the soul pines away, goes mad, and dies exhausted....  What power there is in a meal!...

The transition from animals to man is not abrupt, as true philosphers will admit.  What was man before the invention of words and the knowledge of language?  An animal of his own species with much less instinct than the others.  In those days, he did not consider himself king over the other animals, nor was he distinguished from the ape, and from the rest, except as the ape itself differs from the other animals, i.e., by a more intelligent face....

Words, languages, laws, sciences, and the fine arts have come, and by them finally the rough diamond of our mind has been polished.  Man has been trained in the same way as animals.  He has become an author, as they became beasts of burden.  A geometrician has learned to perform the most difficult demonstrations and calculations, as a monkey has learned to take his little hat off and on, and to mount his tame dog.  All has been accomplished through signs, every species has learned what it could understand, and in this way men have acquired symbolic knowledge....

As a violin string or a harpsichord key vibrates and give forth sound, so the cerebral fibers, struck by waves of sound, are stimulated to render or repeat the words that strike them.  And as the structure of the brain is such that when eyes well-formed for seeing, have once perceived the image of objects, the brain cannot help seeing their images and their differences, so when the signs of these differences have been traced or imprinted in the brain, the soul necessarily examines their relations--an examination that would have been impossible without the discovery of signs or the invention of language....

[I]magination is the soul....  By the imagination, by its flattering brush, the cold skeleton of reason takes on living and ruddy flesh, by the imagination the sciences flourish, the arts are adorned, the wood speaks, the echoes sigh, the rocks weep, marble breathes, and all inanimate objects gain life....

Man is not molded from a costlier clay; nature has used but one dough, and has merely varied the leaven....

[T]he soul is clearly an enlightened machine.  For ... even if man alone had received a share of natural law, would he be any less a machine for that?  A few more wheels, a few more springs than in the most perfect animals, the brain proportionally nearer the heart and for this very reason receiving more blood--any one of a number of unknown causes might always produce this delicate conscience so easily wounded, this remorse which is no more foreign to matter than to thought, and in a word all the differences that are supposed to exist here....

Given the least principle of motion, animated bodies will have all that is necessary for moving, feeling, thinking, repenting, or in a word for conducting themselves in the physical realm, and in the moral realm which depends upon it....  [T]hose who perhaps think that all the difficulties have not yet been removed shall now read of experiments that will completely satisfy them.

1. The flesh of all animals palpitates after death....

2. Muscles separated from the body contract when they are stimulated.

3. The intestines keep up their peristaltic or vermicular motion for a long time.

4. According to Cowper [English anatomist, William Cowper (1666-1709)], a simple injection of hot water reanimates the heart and the muscles.

5. A frog's heart moves for an hour or more after it has been removed from the body, especially when exposed to the sun or better still when placed on a hot table or chair.  If this movement seems totally lost, one has only to stimulate the heart, and that hollow muscle beats again.  Harvey [English physician and physiologist, William Harvey (1578-1657)]made this same observation on toads.

6. Bacon of Verulam [English statesman, philosopher, essayist, Francis Bacon (1551-1626)] in his treatise "Sylva Sylvarum" cites the case of a man convicted of treason, who was opened alive, and whose heart thrown into hot water leaped several times, each time less high, to the perpendicular height of two feet.

7. Take a tiny chicken still in the egg, cut out the heart and you will observe the same phenomena as before, under almost the same conditions.  The warmth of the breath alone reanimates an animal about to perish in the air pump....

8. The caterpillar, the worm, the spider, the fly, the eel--all exhibit the same phenomena; and in hot water, because of the fire it contains, the movement of the detached parts increases.

9. A drunken soldier cut off with one stroke of his saber an Indian rooster's head.  The animal remained standing, then walked, and ran:  happening to run against a wall, it turned around, beat its wings still running, and finally fell down....

10. Polyps do more than move after they have been cut in pieces.  In a week they regenerate to form as many animals as there are pieces....

Let us now go into some detail concering these springs of the human machine.  All the vital, animal, natural, and automatic motions are carried on by their action.  Is it not in a purely mechanical way that the body shrinks back when it is struck with terror at the sight of an unforeseen precipice, that the eyelids are lowered at the menace of a blow, as some have remarked, and that the pupil contracts in broad daylight to save the retina, and dilates to see objects in darkness?   Is it not by mechanical means that the pores of the skin close in winter so that the cold cannot penetrate to the interior of the blood vessels, and that the stomach vomits when it is irritated by poison, ... that the heart, the arteries and the muscles contract in sleep as well as in waking hours, that the lungs serve as bellows continually in exercise, ... that the heart contracts more strongly than any other muscle?....

[M]an is but an animal, or a collection of springs which wind each other up....  If these springs differ among themselves, these differences consist only in their position and in their degrees, and never in their nature; wherefore the soul is but a principle of motion or a material and sensible part of the brain, which can be regarded, without fear of error, as the mainspring of the whole machine, having a visible influence on all the parts....  This oscillation, which is natural or suited to our machine, and with which each fiber and even each fibrous element ... seems to be endowed, like that of a pendulum, cannot keep up forever.  It must be renewed as it loses strength, invigorated when it is tired, and weakened when it is disturbed by excess of strength and vigor....
Vaucanson's Duck

It appears that there is but one [type of organization] in the universe, and that man is the most perfect [example].  He is to the ape, and to the most intelligent animals, as the planetary pendulum of Huyghens [Dutch physicist, mathematician, astronomer, Christiaan Huyghens (1629-1695)] is to a watch of Julien Leroy [French watchmaker (1686-1759)].  More instruments, more wheels and more springs were necessary to mark the movements of the planets than to mark or strike the hours; and Vaucanson [French mechanician, Jacques de Vaucanson (1709-1782)], who needed more skill for making his flute player than for making his duck, would have needed still more to make a talking man, a mechanism no longer to be regarded as impossible, especially in the hands of another Prometheus.

In like fashion, it was necessary that nature should use more elaborate art in making and sustaining a machine which for a whole century could mark all motions of the heart and of the mind; for though one does not tell time by the pulse, it is at least the barometer of the warmth and the vivacity by which one may estimate the nature of the soul.  I am right!  The human body is a watch, a large watch constructed with such skill and ingenuity, that if the wheel which marks the seconds happens to stop, the minute wheel turns and keeps on going its round, and in the same way the quarter-hour wheel, and all the others go on running when the first wheels have stopped because rusty or, for any reason, out of order....

To be a machine, to feel, to think, to know how to distinguish good from bad, as well as blue from yellow, in a word, to be born with an intelligence and a sure moral instinct, and to be but an animal, are therefore characters which are no more contradictory, than to be an ape or a parrot and to be able to give oneself pleasure....  I believe that thought is so little incompatible with organized matter, that it seems to be one of its properties on a par with electricty, the faculty of motion, impenetrability, extension, etc....

We are veritable moles in the field of nature; we achieve little more than the mole's journey and it is our pride which prescribes limits to the limitless.  We are in the position of a watch that should say:  "I was never made by that fool of a workman, I who divide time, who mark so exactly the course of the sun, who repeat aloud the hours which I mark!  No! that is impossible!"  In the same way, we disdiain, ungrateful wretches that we are, this common mother of all kingdoms, as the chemists say.  We imagine, or rather we infer, a cause superior to that to which we owe all, and which truly has wrought all things in an inconceivable fashion.  No; matter contains nothing base, except to the vulgar eyes which do not recognize her in her most splendid works; and nature is no stupid workman.  She creates millions of men, with a facility and a pleasure more intense than the effort of a watchmaker in making the most complicated watch.  Her power shines forth equally in creating the lowliest insect and in creating the most highly developed man; the animal kingdom costs her no more than the vegetable, and the most splendid genius no more than a blade of wheat.  Let us then judge by what we see of that which is hidden from the curiosity of our eyes and of our investigations, and let us not imagine anything beyond....

Let us then conclude boldly that man is a machine, and that in the whole universe there is but a single substance differently modified.  This is no hypothesis set forth by dint of a number of postulates and assumptions; it is not the work of prejudice, nor even of my reason alone....  Experience has thus spoken to me in behalf of reason; and in this way I have combined the two....

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