René descartes on the localisation of the soul

T H E I R I S H J O U R N A L M E D I C A L S C I E N C E

THE OFFICIAL JOURNAL OF THE ROYAL ACADEMY OF MEDICINE IN IRELAND.

OF

SIXTH SERIES. No. 285° SEPTEMBER, 1949.

!

RENE DESCARTES ON THE LOCALISATION OF THE SOUL. ~

By GEOFFREY JEFFERSON, F.R.S. (Manchester).

" Those who are seeking the strict way of truth should not trouble themselves about any object concerning which they cannot have a certainty equal to that of arithmetical or geometrical delnonstration."--Descartes. R e g u l a e .

T HE localization of the soul by Descartes in the pineal gland is a fact known to most educated people. A study of it is not without a certain timeliness, because this year marks the tercentenary of

the book, Les P assion~ de l'Ame (1649), in which Descartes first published a full statement of his beliefs on the soul and the pineal gland. Those wl~o have not studied Descartes' writings are puzzled by his selection of the pineal, because to the pl~sent-day mind a more unlikely place could hardly be conceived. Yet we can be sure that so subtle and so intelligent a man must have had such good reasons for his choice and such ample argument to defend it as to pass his own critical scrutiny and to convince a host of other intelligent men. I t may, therefore, be of some interest if, as neurologists, we trace the develop- ment of the idea in Descartes' mind, and see what place it occupied in his philosophy. For this purpose we must remind ourselves what manner of man Descartes was, and what were the circumstances of his life.

Descartes was born (1596) during the closing years of our own Queen Elizabeth's reign, and his life extended over the reigns of the first two Stuart Kings. He was a gentleman of good birth, of modest indepen- dent means. He had been educated at one of the most famous of European schools, the Jesuit College of La Fl~che, then newly founded by the great French reformer-King, Henry IV. After a youth spent as a peripatetic volunteer army officer in foreign employment in Holland and Germany (no uncommon custom with the younger sons of the landed gentry of those days), seeing service on the Danube and being present at the storming of Prague, he withdrew to the seclusion of Holland, and remained there in privacy and unmarried all his life in order to dedicate himself to natural philosophy and metaphysical speculation. His life as a soldier strikes present-day generations as having been that of something of a military dilettante, though episodes are narrated that testify

*Being the John Mallet Purser Lecture delivered in the School of Physic. Trinity College, Dublin, 26th May, 1949.

692 I R I S H JOURNAL OF MEDICAL SCIENCE

to his resolution and personal courage. Even in his military postings he sought out the scholars, and especially the mathematicians, and, whilst on service with the Prince of Orange, composed his first ingenious work, Compendium Musicae (1628) on the logical arithmetical basis of musical sounds. He spent the last twenty years of his life in Holland, visiting Paris only three times, preferring a life of retirement and seclusion from social duties. His most happy years seem to have been those spent at Egmond, in a small house (no longer existant), attended only by his carefully-chosen servants, in a tiny village behind the sand-dunes, an isolated spot to this day. Cloistered from the world he pursued his famous recherche pour la veritY. Not for nothing, as others have observed, was his motto Bene qui latuit, bene vixit (he lives well who is well masked). The keynote to Descartes' psychology is his confession, in the famous Discours, that at an early age he had become fascinated by the logic, simplicity and certainty of mathematical proofs. How delightful they were in contrast with the turgid obscurities of the ancient philosophers and their mediaeval apologists and commentators who had taught him nothing definite and were best rejected, a conclusion later reached by David Hume. Would it not be possible to use instead the method of mathematics, and by breaking down any kind of proposition into its simplest and easiest terms, find truths so clear and so distinct (i.e., separate), that they brought instant and lasting con- victions? This proposition profoundly influenced all European thought, and survives to-day, though his was the approach of a thinker rather than of an experimenter, and will not do alone. So bare a statement o f a scientific method of universal application gives no more than the merest hint of the quality of one of the richest minds in history, but it may serve to suggest how Descartes would proceed to explain and analyse the passions (the emotions), and, with the aid of anatomical research, to explore the nature of thinking and of the soul. We shall find him, as befitted the inventor of analytical geometry, bringing to bear on brain physiology a linear mechanistic geometrical plan to replace the semi-magical explanations previously current, and giving explanation in terms of dynamics where none before had been attempted.

Descartes as Anatomist.

It is evident from Descartes' letters, as well as from his writings, that he was deeply intrigued by medicine. His preoccupation was a good deal personal, for, having been expected to inherit his mother's ehest weakness, he had been coddled and given special privileges at school where he had been allowed to stay in bed late in the morning, a habit that remained with him all his life. In these hours he was wont to meditate and work; although his health was good, h e was a valetudinarian much influenced by the idea of illness and its prevention. He believed that if one knew how to live correctly long life could be ensured, even to 100 years. He tells this to Huygens (18th February, 1638), and says he is working on an Abrggg de Mgdeclne (lost). The golden rule was to live quietly, to avoid the intrusions of society, and especially to escape from quarrels. Alas! it was his fate to be continually involved in some major dispute in philosophy, religion or mathematics, though always at a very high level. It was with professors

REN~ DESCARTES ON THE LOCALISATION OF THE SOUL 693

and universities that he quarrelled. He died of pneumonia in a bitter winter in Stockholm, at the early age of 54, a fact that did not escape the gibes of the uncharitable. But as he told his friends, if he could not prolong his own life, at least he had succeeded in banishing the fear of death. At what age he started on his medical studies is unknown. Baillet said that he learned something of it whilst a boy at La Fl~che, but this is doubtful. Our first documented fact comes in 1637, when he was 41, but it is of such a nature as to make it certain that his inquiries had gone some distance already. Baillet says in his famous Vie de M. Des Cartes that he started dissecting the parts of animals obtained from butchers soon after he arrived in Holland, 1628. in 1637 there are two references by Descartes himself. In the letter to Huygens (mentioned above), he confessed that he was studying medicine, needing the knowledge for part of his projected book, D6 mundo.* This work was to have demonstrated that a method (already mentioned) existed by which all science could be studied : the nature of the universe, the movements of the planets, the structure of plants and animals, emerging finally with proof of the existence of God. That at least was its plan, but its publication was not proceeded with after the condemnation of Galileo in 1638, because Descartes could not be sure that others would not find heresies in his text, though his conscience was quite clear. He neither desired to hurt other people's feelings, nor to have writings of which he was proud suppressed. The little that eventually remained of this ambitious work was published posthumously in Paris in 1664, Le Monde de Mr. Descartes ou le Trait~ de la Lumi~re (an anticlimactic sort of title when we remember that the "world " meant the "universe") . Clerselier added to his own French edition L'homme de Rend Descartes et uu Tra~tg de la formation du Foetus (1677).t I t seems plain that the addition of the anatomical studies in this latest edition restored somewhat the ambitious original plan of Descartes, whilst other parts of it, elaborated and enriched by further thought and experience, were no doubt used in the Meditatians and certainly in the Princlpia and Passions. Descartes' second reference in 1637 to anatomy comes from the Dioptrics of 1637, and will be given later, because it brings in the pineal gland.

Descartes is known to have had but a small library, and to have been no great reader, but he must have studied medical works as well as dissected parts. He preferred thinking and writing to the drug, reading. The great anatomical textbooks of Stenson (1669), Y ieussens (1685), Willis (1664), and Bartholin (1673) saw the light too late for

* I n a l e t t e r wr i t t en long a f te r to t h e P r incess F, t i sabe th (31 J an . , 1648) Desca r t e s s a y s t h a t he h a s on b a n d a work desc r ip t ive o f t h e f tmc t lons o f an lma] s a n d m a n . H e adds t h a t he h a s b e e r work i ng on i t for 12 or 13 years . No d o u b t t h i s was Le Tra~td de l 'Homme, t h a t r e m a i n e d u n p u b l i s h e d in h i s l i fet ime. The ea r ly " A b r i d g e m e n t o f Medic ine " p r o b a b l y m e r g e d i n t o i t , for Descar tes , like m a n y th inke r s , p ro jec ted v o l u m e s t h a t were neve r w r i t t e n or b e c a m e changel ings .

t T h e r e were severa l ed i t ions w i t h di f ferent edi tors a n d w i th va r i ous c o m b i n a t i o n s o f c o n t e n t s : De t tomine ed. F l o r e n t Sehuy l Leiden. 1662 ; Le Monde de Mr . Descarte~s ou le TraitS" de la Lumi~re ed. d 'Al iber t . Pa r i s , 1664 ; L" t tomme de Rend Desea~es e t un Traitd de la Formation du Foetus ( con ta ins r e m a r k s b y de la Forge) ed. Clerselier. Par i s . 1664 ; L ' Homme de Rend Descartes et la Formation du Foetus avee los Remarques de Louis de la Forge et Le ,Vlonde ou Traitd de la Lumi~re 2nd edn. Clerselier. Pa r i s , 1677.

694 IRISH JOURNAL OF MEDICAL SCIENCE

Descartes' use. Gilson, in a penetrating survey of the medical teaching of the early 17th century, shows that the classical biological textbooks were Aristotelian, ~he chief text being that of the Jesuits of the famous and ancient Portuguese University of Coimbra. This would be, Gilson believes, the most probable source of physiological knowledge at Descartes' College, La Fl~che, and certainly, despite his resolve to rid himself of the follies of ancient doctrines, he could not empty his mind of their teachings, as some of his statements show. As an antidote, the anatomy of Vesalius would naturally be available, but since Vesal is weak on the nervous system and the uses of the brain, it would not help him. Nor is there any evidence that Descartes had heard of Fernel. We know that he had read Harvey's de Motu Cordis (1628), because he has said so, and admitted his conversion to it, except that he did not believe that the heart was a muscle, preferring to invent his own gas engine theory of the heart beat--and fantastic it is. But his interest in the heart, and the fact that he was familiar with it by dissection, had seen it beating after death in animals, is certified by his long letter to a doctor of Louvain (name unknown). I t would astonish us greatly to-day if the Sadlierian Professor of Mathematics or the Astronomer Royal were to publish a work on anatomy. Things were different in the 17th century, for science was a general subject; the early history of the Royal Society shows how catholic were the in~erests of its Fellows; anatomy was anybody's game. It would seem quite natural in the 1630's and 1640's that a gifted man like Descartes should have his say, although reading between the lines of the criticisms of his work we receive the impression that he was already detected by the professionals as an amateur in anatomy. It would not be an exaggeration to say that most philosophers, especially the metaphysicians, even of our times, have felt a great need of neuro-physiological knowledge. A . N . Whitehead once admitted his regrets at not having studied medicine.

Descartes' Anatomical Studies. The most impressive evidence of all is furnished by the Excerpta

Anatomica, and Primae Cogitationes circa Generationem Animalium, rejected by Victor Cousin, but accepted by Adam and Tannery as authentic. Two hundred years elapsed before this text, of which the originals are missing and the exact date of composition is unknown, saw the light. A. and T. think the letter might have been started as early as 1629. It is a kind of anatomical commonplace book. It was printed (1859-60) by Foucher de Careil, the editor of Leibnitz's manuscripts, from a copy found in the Royal Library of Hanover. Leibnitz was only four years' old when Descartes died, but he evidently read his manuscripts as well as his published works before he conceded, as he did, that "Descartes was the ante-chamber to the truth ". The Excerpta is mainly about the heart and generation in animals, but there is a section on the sheep's brain that mentions the pineal as a " p e n i s " obturating a passage (pre- sumably the aqueduct or 4th ventricle). No reference is made to pineal function. The Excerpta and the Treatise on Man and the Formation of the F~tus together made up a large body of medical material, much of which is speculative. He used body structure, not as we moderns do as an observational study, but as a meagrely factual basis for theory,

REN]~ DESCARTES ON THE LOCALISATION OF THE SOUL 695

as man always does when he seeks explanations before his time. It would be fair to say that although Descartes' dissections had been primarily for his own private instruction, he was so pleased with what he discovered that he acquired a zeal to instruct others. In that sense he was a prototype of the popular scientific expositors of the present day, but an exciting one of singular quality.

Another source of medical knowledge must not be forgotten, namely, his friendships with doctors, especially perhaps with Regius (Dr. Henri le Roy), a teacher of medicine in the University of Utrecht. He paid Descartes the compliment of being interested in philosophy, an example that other medical men have followed since, our greatest expositor having been, of course, John Locke. Regius wrote a medical work (see later), based on Descartes' physiology. By conversation and by letters Descartes and le Roy kept in close touch (until the latter became an enemy), and we can be sure that, in general, Descartes, in spite of his unapproachability, was always ready to pick the brains of medical men selectively whenever they had any knowledge that would be useful to him. By all these means he accumulated the body of knowledge necessary for his pronouncements on the workings of the nervous system, and the situation of man;s soul.

T h e S o u l .

At this point we find ourselves in need of some clarification of the meaning of the word " soul ". For us it has, except in poetry, a purely religious meaning, but in the 16th century its connotations were more ambiguous because they derived from the various uses to which the word a n i m a had been put by the ancients. Thus there were originally three different souls, the vegetative, the sensitive and the reasoning ~. These had been the designations of pre-Christian or non-Christian thinkers, but had been adopted by religious men who attached immortality chiefly to the third, the reasoning, soul, though there was no complete uniformity of practice. I t is not possible to translate the vegetative and sensitive souls absolutely accurately into physiological language, because the ideas behind them are obsolete. The first implies the quality by which a body is alive, the second that by which it not only feels but moves (it is a surprise to us that for so many centuries a sharp distinction between these two different nervous actions, sensory and motor, was not drawnwDescartes himself was confused), the third that by which the individual owning it thinks and, having judgment of events, is responsible for his actions. We come as near as we can to modern paraphrasis by calling these three souls autonomic, reflex, and mental. To Descartes the word " soul " meant only the third, the reasoning or mental soul, because he was able as the result of his mechanical interpretation of bodily actions to get rid of the first two. He believed that the animal was a machine, and he showed in word

1The O.E.D. definitior~s o f soul r evea l t h e pe rs i s t ence o f t he th ree souls o f t h e a a c i e n t s in t h e s t r u c t u r e o f our l anguage . A m o n g s t i t s m a n y a l t e r n a t i v e m e a n i n g s a re : t h e i m m a t e r i a l p a r t o f m a n , d i s e m b o d i e d spir i t , t h e mora l a n d emo t iona l p a r t o f m a n , t h e in te l l ec tua l p a r t o f m a n . Or i t c an m e a n t h e v i t a l pr inc ip le a n d m e n t a l powers o f b o t h a n i m a l s a a d m e n . All t he se i n t e r p r e t a t i o n s can be found m u l t i p l i e d aga in a n d aga in i n t h e v a s t w e a l t h o f sub t l e u se s to wh ich t he poe t s h a v e p u t t h e word f r o m " M y soul is a a e n c h a n t e d b o a t , " a n d " G o soul , t h e b o d y ' s g u e s t " to t h e a l m o s t phys io leg ica] ' " H e a r t a n d t h e soul a n d t h e senses . "


pictures and by similes and in diagrams that all the actions of an animal could be, and therefore were, explained as the results of prefixed mechanisms. The animal's pineal was part of this mechanism, a central part. The animal's life was that of an automaton, much more perfect than anything which man had yet made with his own hands, and therefore very deceptive to the vulgar eye. Yet it was a machine, no less, pineal and all, and alive only because of the heat in its heart--a sad fall, this last, on Descartes' part back through fifteen centuries to Galenic medicine and the " fire in the heart ". Although Descartes does not everywhere use the word " reflex ", yet animals were for him purely reflex things that could not think. Few had ever believed that they could, for had it been admitted that they thought some nasty problems in their entitlement to immortality and salvation would have arisen. Descartes realised this as he showed in a letter to the Cambridge ned- Platonist, Henry More, where he says: " If they thought as we do, they must have an immortal soul, which is not likely, as we have no reason to extend to it some animals without extending it to all, such as worms, oysters, sponges, etc." There was no clear authority in the Scriptures for such a belief, though there were passages that declared God's interest in the welfare of dumb creatures. On the whole it was a subject best left alone, since it degraded man, and the World was far from prepared for the shame of the Darwinian theory.

The animal, then, required nothing more than its own " works " t o make it go, it needed souls no more than did a clock or a water-wheel. Descartes said as much: " There is no need to conceive in it another soul, vegetative or sensitive, nor any other principle of movement and of life except the blood and the animal spirits agitated by the heat which burns continually in its breast." This sufficed completely for animals, and to a large extent for men. It could be proved geometrically by means of lines on paper, that most behaviour was produced automati- cally. Yet there were still to be accounted for man's particular qualities, which were mental. Man was a mental animal. The highest forms of thought, the reason, right judgment and the will, were found only in man, and were attributed to the presence of the one thing the animal had not got, the soul, and the soul was in the pineal gland in man alone. This is the famous dualism of Descartes, i.e. (a) all the very intricate and perfect actions which were common to men and animals were prefixed, the unavoidable results of structure, they were physical, mdeh- anical, and automatic; (b) by contrast, the highest forms of intellect belonged to the spirit, and were given by God only to man with his soul. Both soul aad mind had somehow to be attached to body. Ought not a good anatomist be able to say where these qualities resided in the brain? The world thought so then, some of it thinks so now. There was, unhappily, nothing in its gross anatomy that leapt to the eye as the obvious seat of the soul, nothing in man's brain that was not recog- nisably present in the animal as well. Failing anything thus singular for the soul's lodgment, it would have to be discovered by argument, and argument ran something like this: its situation would have to be the most convenient possible for the concentration in small compass of all impressions (sensations), because in that way the soul's judgment could most quickly be passed on what was happening, a n d decisions


made. It would be a neat and elegant solution, like that of a difficult mathematical theorem, if it could be shown that the site of man's soul was identical with the central receiving and distributing station of the animal which, Descartes thought, was the pineal, and so the gland became the nodal point of Cartesian dualism. This is, in brief, the whole tale of Descartes and the pineal gland, but we have still to follow its rationale in Descartes' own words.

Whereas the outline just given will cause the reader to believe that the soul was contained wholly within the pineal gland, it was, for Descartes, its cerebral site. This infers that it had others. I t had no other specific and nameable locations, it was a unity diffused besides throughout our bodies. The justification for this statement will be found in The Pazsians, Article 31, shortly to be quoted, and more imprecisely in his letters. But it is nevertheless clear that Descartes thought that the principal seat of the soul was in the pineal, for how else could it judge and influence our conduct (Passions, Art. 41)?

It is clear t h a t " soul" evidently meant mind as well as the immaterial principle of immortality. I t must mean both things because no one had ever been able to conceive survival after death without a mind to verify the fact of continued existence, to enjoy its pleasures or suffer its pains. Hence we find theologians, savants, philosophers, and the medical world alike using soul with a double meaning, but when they wished, in an entirely psychological sense, as the psyche without any religious impli- cations. This usage has survivedto our own day. I t was as mind that Descartes used it in his anatomical and physiological writings, though its other signification was always in his thoughts as well, as it is in ours. So, in his metaphysics, whilst fortified by his knowledge of the anatomical substratum of mind, he could treat it in its widest sense, whilst, in his mechanics, he could concentrate on mental attributes alone.

Descartes and the Pineal Soul.

We now come to the reasons for which Descartes chose the pineal as the focal point of thinking, and as the dwelling place of the soul. I t is a nuisance that it is not possible to give an accurate account of his statements so that they read as a consecutive narrative. This is because his reasons were given in four different places, as follows: (1) the Dioptrics, 1637; (2) three letters to Mersenne, 1640; (3) The Passions, 1649; (4) the Treatise on Man, Latin version, 1662, French, 1664. We can add to this his vivid statement of the animal as a machine in the Discours (1637), though the pineal is not introduced there. Each one of these sources is complementary in some respect to the others: the most complete anatomically is the posthumous L'Homme. Let us begin with the fullest statement published during his life-time. It will be found in Article 31 of the Passions of the Soul. The passage represents his mature judgment published only a few months before his death. The English translation, by an unknown hand in 1650, runs as follows :

" I t is also necessary to know tha t although the soul be joynod to all the body, yet there is s o m e part in tha t body w h e r e i n she exercises her functions more particularly than all the rest, and i t is commonly believed tha t this part is the brain, or i t may be, the heart : t h e bra in because thi ther tend the organs of the senses , a n d t h e heart


because therein the P a s s i o n s are felt ; but having searched this business carefully m e thinks I have p la in ly found out tha t tha t par t of the body wherein the soul immediately exerc ises her functions is not a jot of the heart , nor y e t all the brain but o n l y the most interior par t of it, which is a certain very small kernel si tuated in the middle of the substance of it, and so hung on the top of the conduit [aqueductus Sylv i i ] by which the spirits of its anterior cavities [lateral and third ventricle] have commtmication with those o f the poster ior , whose least m o t i o n s in i t cause the course of the spirits very much to change, and reciprocally, the least a l terat ions befalling the course of the spirits cause the m o t i o n s o f the kernel very much to alter."

The passages quoted require no little elucidation if we are to comprehend them in the way which their author intended, because they are not intrinsically very clear.

The fundamental proposition in Descartes' theory of the pineal gland was, unfortunately for him, based on so complete a misconception as to destroy it. His mistake was to regard the lining of the ventricle of the brain, to him the concavities, as the chief nervous structure. The cerebral cortex was no more than a vascular area supplying the brain with nourishment. This sounds in our ears to be an egregious error, but it is very possible that none of us, had we lived in Descartes' time, would have detected it. The belief that the properties of the mind resided in the ventricles was well-founded by tradition, and it would follow that the walls of these cavities were important membranes. Mediaeval medical writers had published diagrams of the head that showed " ventricles ", anterior, middle, and posterior--and it was there that the various psychological processes were carried out. Thus in the figure (Fig. 1) from Albertus Magnus (1490), we see imagination and common sensation, memory and motion assigned to their internal locations. All writers from Saint Augustine on to Saint Thomas Aquinas, Lanfrane and Guy de Chauliac, had also made their attributions, of which the most common was of movement to the posterior ventricle. This might have originated in actual observation of movements of the limbs when the brains of animals were damaged experimentally (e.g., by Galen), but for the rest the diagrams were pure speculation, and anyone was entitled to have his opinion. The important thing was that it was the ventricles that mattered most. Clearly they must be pre- dominant because they were filled with the nervous energy of the subtle, volatile, invisible, and immaterial animal spirits, I would not say that everyone without exceptiol~ concurred, but Shakespeare, who was, after all, only one generation older t h a n Descartes, wrote : " These are begot in the ventricle of memorie, nourisht in the wombe of pia mater, and delivered on the mellowing of the occasion." These refer to the extra- vagances of the imagination " f u l l of formes, figures, shapes, objects, ideas, apprehensions, motions, revolutions ". This is poetic language, it is true, but poets have a way of being mouthpieces of the knowledge of their times. Let us not therefore close our Descartes in indignation, bu t t ry to understand him, otherwise we shall miss the first attempt, im~ perfect though it was, to give a dynamic interpretation of the basis of mental actions. We have then to force ourselves to agree for the moment that the most important layers of the brain line the ventricles. The next significant thing lies in the fact, mentioned above, that it was in the D i o p t r i c s that the pronouncement on the pineal was first made; speaking of an object seen he says:

~ = ~

, /

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Z

Brixiae, Bapt. de Farfen~o, 149o. H, iH*~+-Ilm,-.~ehemata, aL, s d. I), 'ueken d. l'hilosoph.ia Natural is des Alher tus

Magnus. F~<:. ~. A]bertHs Ma~nu~, 1.190, d iagram of the se'~t of intelleeimM qualitivs m

~he three ventricles.

FIG. 2. Sensa t ions f rom the scorched foot pas s ing up a nerve to tile vent r ic les caus ing wi thd rawa l of foot, t u r n i n g of he~d and eyes and

m o v e m e n t of hand .

FI(~. 3. The rows of circles are the open ends of nerve tubes leaving the ventricl.es, impulses from the uncrossed (herbivorous) chiasma crossing onto

the pineal. Observe the " floating " pineal glan,d.

FIG. 5. Sensations from re t ina overpowering those from tile nose--smell of the rose not noticed (olfactory impulses dot ted lines).

FIG. 4. impulses J)-m~l tlle r e t imt caus ing reflection ot' an ima l spi r i t s from the vent r ic le in to the a p p r o p r i a t e nerve tl lhes for movement of

the Arm. (Tra i t6 de l 'Homrn(,, 2nd edn. 1677.)

REN]~ D E S C A R T E S ON T H E L O C A L I S A T I O N OF T H E SOUL 699

" I t is mani fes t that i t f o r m s a picture aga in on t h e i n t e r i o r s u r f a c e s o f the concav i t i e s o f t h e brain, suff iciently s imilar to t h e object , a n d from these I c o u l d transfer i t to

certain l i t t le g land which is to be found about the m i d d l e o f the cav i t i e s and is r ight ly the seat o f the c o m m o n s e n s e . "

The significance of this statement is that Descartes came to apply the same explanation that he here uses for vision to all pereepta, making all sensations whatever focus also on the gland. There are diagrams in the text of b'ttomme i l lustrative of this made by Louis de la Forge and G~rard van Gutsehoven from the author 's now lost sketches, or else worked up f rom the text. These show an arrow reflected on to the retina, whence it was carried along the optic nerve by the anlmal spirits (=nervous impulses), to emerge through the pores of the optic nerve tubes and converge on to the pineal which sat diagrammatically in the middle of the ventricle. There the arrow appears again as a point to point representation on the pineal's surface, which is good dioptries. From here again it is reflected in a straight line by the animal spirits which filled the ventricles to enter the open mouth of other nerve tubes along which the spirits coursed to the muscles which would cause the action most appropriate to the object seen. The pineal funct ioned in this way as a reflector of all sorts of sensations, whether f rom the special senses, or f rom the general surface of the body, and always the same thing resulted, an action proper to the stimulus felt. As Souques (1945) has r ight ly said, Descartes' studies in dioptries profoundly influenced his neurological theories. They are fundamental to the pineal theory. The illustrations show various actions. For instance in Fig. 2 is shown the effects of a burn on the foot. The burn influences (Descartes said " pulls ") the nerve so as to open the pores in the ventricles so as to cause several things to happen : (a) the head and eyes t u rn towards the fire, (b) the arm goes down to the foot, (c) the leg is withdrawn. The lanceolate object depicted in the brain is the ventricle, the pineal is not shown. In Fig. 3 the ends of the optic nerves are drawn as opening. into the ventricles, the row of circles represents the open ends of many other nerve tubes; the pineal lies in the middle held down by fine branched vessels. In Fig. 4 the pineal is shown ful ly in action, t h e arrow is represented on the pineal and is reflected into motor channels proper to the sight of the arrow. In Fig. 5 a rose is being smelled also, but it is not noticed as the nerve currents are depicted by dotted lines as less insistent. T h i s is bad anatomy, but it is good psychology.

I have said that the animal spirits were reflected by the pineal, but it was not as simple and unin ter rupted an occurrence as that. What really happened was that the pineal itself emitted its own spirits that crossed the ventricles to selected nerve pores. Hence the pineal was essentially a selective motor organ. Descartes is not always clear on this mechanism because he does not realise the necessity to make very clear distinctions between sensation and movement, but no one else then recognised it.

In the diagram the over-sized pineal was drawn purposely in magni- fication for the sake of clarity. The pineal is shown with no actual continuity with nervous tissue, but is tethered to the brain by a large number of very fine arteries, which are visible in these diagrams, so that it was mobile and was suspended in the whirl of animal spirits dancing and jigging, as Descartes himself said, like a balloon captive


above a fire, or like a ball dancing in a jet of water. I t was the force of the animal spirits which caused these movements, and these were always appropriate to the stimulus. The particles of the animal spirits were coarser when they had an emotional basis, and caused the gland to bend over more. This sort of action was common to man and brute. In man alone the pineal had a particular inhabitant. I t was the soul, which took note of all the impressions that came flowing in, which scrutinised and judged them, and so produced an action consistent with wisdom. It was thus the soul that gave to man the choice between the reflex or inevitable answer which he, as an animal, must make to a given stimulus, and that which he alternatively might make as a thinking and rational being (res cogitaz~s).

Enquiries and Explanations. Descartes died in Stockholm (11th Feb., 1650), at the Court of that

famous, but disappointing, young blue-stocking, Queen Christine, too soon after the publieation of the Passions for him either to receive criticisms or to answer them. He had had grave misgivings about this visit of instruction, and matters turned out as badly as he feared. The Queen was an early riser, and preferred to talk at 4.0 a.m. Not only that, but the privacy that he had sought for so many years was destroyed by the social duties of the Court. Furthermore, he found the climate of the Swedish winter very trying. Such a disturbance of the routine of a middle-aged bachelor could scarcely fail to be disastrous, and so it proved since, after nursing his friend, the French Ambassador, Ch~nut, through an acute lung infection, he died of the same thing (possibly influenzal pneumonia), within little more than four months after his arrival. Fortunately for us, Descartes, for a long time previously, had made no secret of his views on the soul and its pineal habitation. I t was evidently sufficiently a subject for private discussion to have reached far afield, and so we have the objections of two doctors, Villiers and Meysonnier, who had come to hear of it. They did not agree with Descartes. They said that the soul was not in the pineal but in the " fixed spirits " (an ambiguous statement), it was in the whole brain of which conarion was only a little part. Further, they thought the eonarion or pineal was more often corrupted or altered as seen at post-mortem than any other portion of the cerebrum. Hence the soul surely should not be in this little part rather than in any other. They went further and said that if all that Descartes required was a single organ, why had he not chosen the pituitary gland ? That was single, and in their opinion just as appropriate. I t is to be feared that the good doctors here made a bad mistake. Even Descartes was able to correct them on this elementary piece of physiology, for the pituitary was already pre-empted for other uses. Everybody knew that the pituitary gland lay in a hollow in the skull base covered with a fold of meninx and that it was the sump or sink into which the impurities of the animal spirits fell after they had been strained off, passing through the vessels of the rete mirabilis (unfortunately for this theory absent in men). These impurities came down the nose as mucus. Not for nothing did Thomas Willis' student translator, Mr. Pordage, call the pituitary a few years later "the snotty kernel ". Descartes mentioned another


objection, a vital one--the pituitary gland was not mobile. The other questions put by the doctors had to be dealt with more fully. Descartes set out his ideas at length in long replies that he made to Father Mersenne to be forwarded to Villiers and Meysonnier. He wrote (26th Jan., 1640) :

" I will reply here to what you were pleased to ask me touching the use of the little gland called Conarion. My opinion is t ha t th is gland is the principal seat of the soul and the place where all our though t s originate. The reason from which I derive this belief is t h a t I find no par t in all the brain, save this alone, which is not double. Now since we see only one th ing wi th the two eyes. nor hear bu t o re voice with two ears. nor have bu t one though t a t the same t ime. i t m u s t of necessi ty be tha t the different th ings which enter by the two eyes or two ears m u s t go to uni te in some par t of the body there to be considered by the soul. Now it is impossible to find a ny other (suitable place) in the whole head bu t this gland. Further , it is s i tua ted the mos t su i tab ly possible for th i s purpose, to wit in the middle between the cavities etc." (as in Th~ Passions already quoted).

The reader will observe no doubt the idea of the singleness of the thought in the mind, a conclusion which surely has been reached from Deseartes' studies on vision, the fusion of images from two eyes; it is plain that dioptrics were fundamental to his theories of mind. In a further letter of Ist April, 1640, he has more to say about conarion (the Greek word for the pineal) :

" l~ow there is only this gland to which the soul can be t hus joined ; for there is only i t which is not double in the whole head. But I believe t ha t it is all the rest of the brain which serves mos t ly for memory , principally the interior parts , and even also the nerves and the muscles which can serve."

He proceeds to talk about this local memory, e.g., in the learning of the fingering of passages by a lute player where the training of the nerves and muscles seemed to him to cause memory to reside somewhat in the hand:

" Bu t beside th is memory, which depends on the body, I recognize another completely intellectual which depends on the soul only. I should not find it s t range tha t the gland Conarion should be found corrupted in the dissection of lethargics, because it is diseased as quickly as in all the others and want ing to see it a t Leiden three years ago in a woman t h a t was being anatomised a l though I searched for it wi th curiosi ty and knew very well where i t ought to be, hav ing become accustomed to find i t wi thout a n y difficulty in freshly killed animals , it was however impossible to recoguise it. An old professor called Valcher who w a s doing this ana tomy, confessed to me t h a t he had never been able to see i t in any h u m a n body ; th is I believe to depend on the fact t h a t several days are taken to examine the intest ines and other par ts before opening the head.

For the mobi l i ty of this gland I do not want other proof t ha n its s i tuat ion ; for being sus ta ined only by little arteries which surround it. i t is certain t ha t it requires very little to make it move. but I do not believe that it can shift itself much this way or that."

On 30th July, 1640, in another letter to his faithful correspondent and senior school friend, that curious man who acted as a sort of inter- national clearing station for European knowledge in mathematics and philosophy, Father Mersenne,* he wrote:

" As for the letter of this doctor it contains nothing to impugn what I have written of the gland called Conarion ; except t h a t he says it can be altered. [i.e. degenerated or corrupted by disease or old age] like all the brain. This does not prevent it from being the prir~cipal seat of the Soul ; for i t is certain t ha t the Soul m u s t be joined to some par t of the body ; arid there is no point which is as muc h or more subject to alteration than ~hls gland which although very small and very soft is none the less so well guarded in the site where it is that it can hardly be subject to any malady any more than can the vitreous humor of the eye."

* Maria ]l~ersenne has h imsel f come into the news again by the solution in Manchester by electronic means of some problems set by h im on prime numbers .


As for the fixed spirit that the doctor mentioned, although he had, he said, no objection to clever people making suggestions, he was surprised that they chose confused and impossible theories, and the alternative suggestion did not seem, so Descartes replied, to be more intelligible than if Villiers had spoken of a dark light or a hard liquid. However, the doctors were not yet done; he would have been distressed had he known that the doctors would not allow his pineal theory any peace for another century, when they quietly buried it.

Critics of Descartes.

Objections to the ideas of Descartes were raised by the metaphysicians as well as by the doctors. The first enquired how it could be that an insubstantial thing like the soul could have been confined in a space, for Descartes himself had laid it down that the definition of matter was not impenetrability but extension (i.e., measurable location, extending from here to there in three dimensions), whilst immaterial things were im- measurable and could not be located. Another difficulty was the manner in which actions of the soul could be synchronised with those of the animal spirits. This was satisfactorily solved later by Leibnitz's analogy of the two clocks side by side, both telling exactly the same time, illus- trating his great thesis of " pre-established harmonies " between spirit and matter. Faced with such metaphysics we may excuse ourselves in the same manner as Sir Thomas Browne : " as for those wingy mysteries in Divinity, and airy subtleties in Religion, which have unhing'd the brain of better heads, they never stretched the pia mater of mine." We are on more dependable grounds with the Objections of the anatomists, which leave our pia mater relaxed.

We should now enquire whether the identification of the pineal gland with the soul was a wholly original idea of Descartes, the child of his own logic. We shall discover that what was new was the manner in which the gland worked ; new also was its relationship with one particular soul, the rational and immortal, the other two being abandoned as unnecessary. Much had been written before the 17th century about the pineal gland, making its choice by Descartes easier than might be supposed. The whole concept depended on the animal spirits, the entrance and exit of which caused the brain to pulsate. The ventricles had no fluid in them, nothing but this invisible nervous agency. The continuity of the ventricles had also been known from Galen's time : he had supposed that the pineal acted as a gate-keeper, a valve regulating the ftow of the animal spirits to and fro in the ventricles, and therefore vitally important to nervous actions. The idea was so simple, so obvious, so elegant indeed, that it appealed to nearly all the post-Galenic anatomists. Jean Fernel, whose great book, The Natural Part of Medicine (1542), Sherrington believes to be the first real physiological text, also believed in the govern- ing action of the pineal rising and falling with the flow of spirits2

*The uses of the pineal before Descartes were given by Barthol in as follows : ' The funct ion of the pineel is s imilar to t h a t of o ther glands, and part icularly, to preside over the d i s t r ibu t ion of the vessels scat tered th roughou t the cerebrum. Some author i t ies regard it as m e a n t to suppo r t arid s t r eng then the plexus choroidie ; o thers regard it as set like a door ~n f ron t of the aper tu re lead, ng to the fourth ven t r i c l e - - shu t t i ng a r d opening wi th the diastole and systole of the cerebrum ; i t has in fact been observed to m o v e when an inflation is made in to the four th ventricle [arx exper imenta l inf la t ior

RENE DESCARTES ON THE LOCALISATION OF THE SOUL 703

Descartes' work was to accept the primacy of the pineal in relation to the spirits, but to imbue it with a mobility quite different from the simple rising and falling valve action of his predecessors. I t became for him the nodal point of his new mechanical animal and, as we have seen, the control room of man's intelligence. So much did Descartes improve on the beliefs of his forerunners and contemporaries that he eventually undid the pineal gland. His mistake was to be too lucid and too exact. His own accounts are not conspicuously detailed, but they shine brightly in comparison with the nebulous descriptions of others before him. Here at length was something about nervous actions that scientists could grasp firmly and criticise. They were not slow to do so, but before mentioning examples, comment must be made on the score of originality in respect of two essays published by others during Descartes' lifetime. These endowed the pineal with functions similar to those which Descartes soon made familiar. One was by Jean Cousin of Paris in 1641, the other, Funda- menta Physices (1646), by Regius (Henri le Roy), of Utrecht. But, as I have been at some pains to point out, it is perfectly clear that Descartes' physiological ideas were well-known and were the subject of discussions among scientists in Paris and in the Universities of Holland long before he published The Passions. It is very clear that the theses elaborated in the essays mentioned were Cartesian in derivation, and Regius not only admitted it but was proud (at that date) to declare himself a disciple of the Master.

To turn more specifically to criticisms of Descartes. They were levelled at him chiefly on the ground that the pineal was palpably too small a structure to be the repository of such vital and indeed noble functions as he taught. Moreover, the anatomists often found solid concretions in it --pineal chalk or stones, and that in persons whose minds were not unhinged, whose limbs were in no way paralysed. We have already seen Descartes engaged in mild argument with the two commonsense doctors on matters such as these, seen him goaded to some petulance by their questions. Heavier artillery was in action before long. Bartholin, the learned Danish anatomist, quickly raised nine objections in his Anatomia of 1673. They were reprinted and replied to by de la Forge at con-

similar to the insufflation of the carotid by means of a tube in order to demonstrate the circulation of the blood--described p. 502 fin. and 503 inlt.]. Other authorities regard it as intended to store the lumen animale or spiritus animalis. For others, again, the purpose of the pineal is to draw off sludge along the nerves so as to clarify the spinal marrow ; but this function of drawing off and draining sludge might fittingly be assigned to the arteries of the conarion (and not to the nerves)--and for this reason : although at the pineal the vein is seen to be larger than the artery and capable of taking away more mat te r than had been brought by the artery, yet since no oozing discharge of fluids has ever been observed at this place the greater capacity of the vein may be accounted for by the fact that i t has to cope with cooled humors. Another theory of the pineal 's function is tha t i t takes in serous fluids from the arterial blood and retains them until they are absorbed again either by the veins or by the lymphatics if any lymphatics are near.

Descartes and his followers, Meysonnier, Regius, Hogelande, think tha t this gland placed as it is in the middle of the ventricles which are on the alert and constantly distended with spiri tus; (1) receives the impulses of all presentations and (2) tha t t h e soul, residing in this gland and this gland only, by means of these impulses apprehends, as though at a centre, external sensations and all ideas originating in the five senses and distinguishes between them and then by the help of the glandsends spir i tus to the various nerves- - jus t as exactly as on a small spherical mirror all objects are received in precisely tha t order in which they exist in the open field or in a work-room." (Anatvmieo pp. 496-7, 1673. Prof. W. H. Semple's translations.)


siderable length in the French edition (1677) of De Homine . We need not trouble ourselves with all of them, but one or two may usefully be recalled. Bartholin pointed out that Sylvius' description of the attach- ment of the pineal to the brain was correct, it was not the mobile structure of Descartes' imagination. Further, he added, it was often larger in animals than man. Admitted, de la Forge replied, but a small object can move quicker than a large one and the gland looks less after death than it actually is--a safe statement at a time when no one had seen the pineal in a living man though maybe they had seen it in live animals, though he does not say so; it was larger or smaller according to the amount of animal spirits contained in it. Bartholin, of course, like the good observer that he was, had seen concretions in the pineal. ~¥hat was more damaging to the Cartesian theory of nerve impulses was that Bartholin had the courage to say that he had often seen a good deal of fluid in the ventricles, fluid that must impede the movements of the spirits if they acted as Descartes believed. Worse still, Bartholin could find no trace of the tiny pores, the open nerve tubes in the walls of the ventricles so essential to the Cartesian theory. De la Forge makes a derisory answer : " There are two ways of discovering the existence of a thing, one by the senses, the other by the reason." Observation was well enough in its way, but when it failed, reason could not only assure us that a thing was probable, but, much more than that, that it was true. Anybody, of course, who had the temerity to deny this magisterial statement on the primacy of reason would attack the doctrine of the perfection of man's reasoning powers, his dearest possession. But the assault had actually begun, had de la Forge known, for Francis Bacon in his A d v a n c e m e n t o f Learn ing had already written his devastating attack, declaring the unreliability of argument in comparison with factual observation and confirmation.

Sir Kenelm Digby, soldier, adventurer and scholar, friend and great admirer of Descartes though he was, was another who found himself eventually unable to accept the mind's residence in the pineal. It was, he admitted, a most difficult task to discover where it lay. " Show me the soule," he cried, " and I will tell you where it resideth." And if an unpaired mid-line structure was required for it, why there was still another, wrote Digby, to which the function could be allotted, the septum lucidum. And that, said Digby, is probably where the mind lived. What Glanvil had to say about both these theories we shall shortly see. Another critic was Thomas Willis, a much more lively theorist than accurate serutineer of the body's parts, yet he too rejected the pineal and placed the common sensory (i.e., the sum of all sensations) in the corpora striata. He " c o o k e d "h i s illustrations of these bodies in his anatomical works so that they showed the channels (wholly illusory) through which the animal spirits, extreme fast-moving subtle flames without heat, coursed there to be strained as through a sieve for the judgment of the soul which sat in the corpus callosum. Nevertheless, Willis thought that the cortex was the place where the nervous energy originated.

Vieussens, Lancisi, de la Peyronie and Nichalas Le Cat all gave their sanction to the location of mind and soul in the corpus callosum. Lancisi's careful dissection of the corpus callosum during his studies and medita- tions on the seat of the soul led to the discovery and description of the


" stri~e longitudinales ", which bear his name to-day. The evidence of the surgeons, de la Peyronie and Le Cat, makes interesting reading since we find something that is new because it is based on descriptions of patients with verified brain diseases. I n none did they find the mind disordered unless the corpus callosum was destroyed, evidence which seemed conclusive until examples of loss of even this structure was shown to be compatible with relative normality. Bonetus and Morgagni des- eribed calculi in the pineal, and thought there was no room for much else but grit in this gland.

The fact that all these observers and speculators voted for a fixed structure showed better than anything else how fully they had rejected the pineal's movement, for it was that above everything that was the eentral fact in Descartes' theory. Gone too seemed to be the linear representation of thought in reflected lines according to the principles of dioptrics which Descartes so lovingly built up.

So the search went on until the beginning of the scientific period proper in medicine. This date is the middle of the 18th century, the time of Haller and Morgagni, with Hermann Boerhaave as the link, for from then on most doctors began to show more respect for sound scientific knowledge, and more understanding of what its standards were. Obser- vation and experiment on the nervous system were looked at with a gaze no longer dimmed by traditional and mediaeval teachings.

The favourite site from 1750 to 1850 was undoubtedly the medulla oblongata, a structure at those dates that included the pons Varolii. Hailer in Germany thought so in 1750, and so did Solly and Marshall Hall in England in 1850. The reason for this was that it seemed to be a consensus of sensation both cranial and spinal, and hence the most probable site for valuation. But by the middle of the 19th century the doctrine of the cerebral cortex was taking toll of the medullary adherents, the Darwinian theory together with the obvious corticalisation of " mental " man and vast strides in knowledge concerning the nature of the nerve cell and the structure of the cortical grey matter brought about an inevitable change. As we ponder not only on the past but on the present some of us may find ourselves still in sympathy with Alexander Pope's lines :

Thou Filet Great Cause, least understood, Who all my sense confined

To know but this, that thou art good And that myself am blind.

We have watched how the concept of the diffuseness of the soul's and the mind's human habitation in the days of the ancients gave way to a pin-point localisation under Descartes' influence only to escape once again. The diffusion this time was definitively in the grey matter of the brain, but these later excursions require more elaboration than can be afforded here. It is but just to allow the 17th century rather than the 18th to have the last word on a 17th century proposal. We could do no better than to give it to that wise and enchanting scientific divine, Joseph Glanvil. Writing of the localisation of the soul and the theories of Ren5 Descartes and Sir Kenelm Digby he said: " It may be that the San


never saw a more learned pair. And yet as a sad evidence of the in- firmities of laps'd humani ty : these great Sophi fail here of their wonted success in tmridling Nature. And I think Favour itself can say no more of ei ther Hypothesis, than tha t they are ingenious at tempts." This is a wise man's judgment. His own opinion was that it was impossible for Adam's sons to succeed in this quest : " But how the purer spirit is uni ted to this clod, is a knot too ha rd for fal len Humani ty to unty. Wha t cement should unite Heaven and earth, light and darkness, natures of so divers a make, of such disagreeing attributes, which have almost nothing, but Being, in common; this is a r iddle which must be left to the coming of Elias. How should a thought be united to a marble statue, or a sunbeam to a lump of clay ! The freezing of the words in the air in the nor thern climes is as conceivable as this strange u n i o n . . . And to hang weights on the wings of the winde seems fa r more intelligible." So it was, and so in its deepest sense i t still remains.

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Paris, 1677. Idem. Oeuvres de Descartes. Ed. Charles Adam and Paul Tannory. 13 Vols. Paris,

1897-1913. DIG-BY, SIT, I~[~NELM, TWO Treatiees, The Nature and Operations of ydan's 8aule.

1-143. London, 1645. FOUCHER DE CAREIL, A. CO~E. Leibnitz, Descartes etc. Paris, 1862. CTLANWIL, Jos . The Vanity of Dogmatizing. 1-250. London, 1661. GILSON, ]~TIENNE. ~tude8 sur le RSle de la pensde mJdigvale etc. Paris , 1930. GALDSTON, I. Dsscartes and ydodern Psychiatric Thought. Isis., 144. 35. 118-126. ttALDAI~, E.S. Life of Rend Descartes. 1-398. London 1905. KoY~. , A. Entretiens ~ur Descartes. 1.113. l~ew York, 1944. L~NCISL J.M. Dissertatio altera. De Sede cog i~ t i e animm. Venice, 1713. LECAT, CLAUDE, N. The Physical Essay on the Senses. Transla ted from tho French.

1750. MAHAFFY, J .P . Descartes. 1-211. London, 1880. MAI~rrAI~, J . The Dream of Descartes. 1-176. London, 1946. I~EL, MARaUE~ITE. Descartes e$ Ia princesse Elisabcth. 1-137. Paris, 1946. PEY~ONIE, M. DE L&. Obstrvations, par lesquelles on tdche de dgcouvrir la pattie du

Gervcau ou l' Ame exerc,~ ses Fonctiens. Morn. Ac~l . Roy. Sci. 199-218. Paris, 1761. ROTH, LEOS. Correspondence of Descartes and Const~ntyn ttuygcns. 1635-1647. 1-351.

Oxford, 1926. SouQuF, s, A. Glande pln~ale et sspri~s animau~ d' apr~s Descartes. R t v . ~]'ourol. P~tris

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