Mental Development Author

Darwin’s Idea of Mental Development Author(s): Marion Hamilton Carter Source: The American Journal of Psychology, Vol. 9, No. 4 (Jul., 1898), pp. 534-559 Published by: University of Illinois Press Stable URL: Accessed: 20-12-2018 07:44 UTC

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In surveying the rise and progress of the Idea of Evolution, particularly since the publication of Darwin’s “Origin of Species,” in I859, one can but be struck with its increasingly wide application to the interpretation of phenomena in every field of human inquiry. Starting with organic forms it has spread over both the world of living matter and the world of dead. Nay, more, it is now made to cover the facts of consciousness, and to serve as an explanation of the peculiari- ties of mind as well as of those of structure. Existence has come to be regarded, not as a bare fact, but as a continuing process in which there are known or determinable conditions followed by known or determinable results.

That the general concept of Evolution had been widely entertained previous to Darwin’s day is beyond dispute, but it is to Darwin that we owe the definite and concrete form in which it has become potent in many new fields of investigation.

Inseparably bound up with the idea of organic evolution is the idea of mental evolution. That mind evolves seems to have been self-evident to Darwin, the case being granted at once upon its merits, and nowhere do we find him questioning it; how mind evolves he devoted a not inconsiderable portion of his work to showing; but he seems to have rested his problem on that assumption, for he tells us that “I have nothing to do with the origin of the mental powers, any more than I have with life itself. We are concerned only with the diversities of instinct and of the other mental faculties of animals of the same class.” ‘ And again, with regard to sen- sation, he says, ” How a nerve comes to be sensitive to light hardly concerns us more than how life itself originated.” 2

Darwin accepted mind, as he accepted life itself, as part and parcel of his scheme of organic evolution; and he thought widely, though not deeply, upon it. He was emphatically neither psychologist nor metaphysician, and writes somewhat naively to John Fiske, of the ” Outlines of Cosmic Philoso- phy :” “I have long wished to know something about the views of the many great men whose doctrines you give. With

1 Origin of Species, 6th ed., p. 242. 2 Ibid., p. I7I.

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the exception of special points I did not even understand H. Spencer’s general doctrine. I never in my life read so lucid an expositor (and therefore thinker) as you are; and I think I understand nearly the whole-perhaps less clearly about Cosmic Theism and Causation than other parts. …. It pleased me to find that here and there I had arrived from my own crude thoughts at some of the same conclusions with you, though I could seldom or never give my reasons for such conclusions. ”

It is not without some significance, particularly in an attempt to ascertain Darwin’s exact philosophical standpoints, that this letter, mentioning special illumination, was not written until 1874, or eight years before his death, and after the great works of his life had been given to the world. His most mature thought upon psychological matters, or those bor- dering upon the psychological, is given to us in his work ” On the Expression of the Emotions in Man and Animals.” The earliest notes for this are dated 1838; the question- naires from which he obtained much valuable information were sent out in 1867; but the book itself was not begun until Jan., 1871, the rough copy being finished in April of the same year.2 It was published in 1873, or one year before the Fiske letter !

Final causes of things-ultimate realities-seem never to have troubled Darwin; doubtless they did not even come upon his horizon. On these subjects he held essentially the common sense views of the every-day man. He assumed out of hand that it was better to be an ape than an insect; that it was bet- ter to be a man than an ape; that it was better to be a white man than a Hottentot, and that it was better to be a civilized white man than a barbarian; and progress meant for him a movement in the direction of the civilized white man, with all that that entailed of intellectual and moral attainment, and not a movement in the direction of the insect. In the “Origin of Species ” he writes:

“The degree of differentiation and specialization of the parts in organic beings, when arrived at maturity, is the best standard, as yet suggested, of their degree of perfection or highness. We have also seen that, as the specialization of parts is an advantage to each being, so natural selection will tend to render the organization of each being more specialized and perfect, and in this sense higher; not but that it may leave many creatures with simple and unimproved structures fitted for simple conditions of life, and in some cases will even de- grade or simplify the organization, yet leaving such degraded beings better fitted for their new walks of life.”3

1 Life and Letters, Vol. II, p. 37I. 2 Ibid., Vol. II, p. 313. 3 Origin of Species, p. 363.

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His common sense view is again shown in his remarks on beauty.

“We can to a certain extent understand how it is that there is so much beauty throughout nature; for this may be largely attributed to the agency of selection. That beauty, according to our sense of it, is not universal, must be admitted by every one who will look at some venomous snakes, at some fishes, and at certain hideous bats with a distorted resemblance to the human face.”‘

When, in I859, Huxley spoke of Darwin as in the ” front rank of British philosophers, ” 2we are to understand the term as then used to mean what is now generally called man of sci- ence rather than metaphysician. Much of Darwin’s philo- sophical reading and thinking was evidently done late in life, if we may judge from his letters and the books he especially refers to in his later works, many of which were not published until the sixties and seventies; yet a very large part of his work was distinctly philosophical, i. e., dealt with ultimate causal relations of phenomena and their laws, and one, at least, of his books may justly be regarded as a contribution to psy- chology. The problem before us now-Darwin’s Idea of Mental Development -is biological in only the widest sense of the term.

In order to determine what his philosophical creed was, to see the conclusions he reached concerning consciousness and its place in a world-plan, it will be, perhaps, necessary to sum up the important questions presented by an evolutional view of mind, and discover how far he had both formulated and answered them. They are as follows:

I. Does mind come into the causal series of organic evolu- tion at large? Is it actively concerned in progress, i. e., has it a ‘ survival value ? ”

II. If Darwin answers this question affirmatively, how does he define “mind ?”

III. What is the relation of body, and, more particularly, of brain to mind ?

IV. What evolves in “mental evolution,” -mind, body, or both mind and body? If mind only, how can it influence organic evolution ? If body only, how does its evolution carry with it the evolution of mind ? If both, what is the course of “mental evolution ?”

To these questions I shall endeavor to find answers in Dar- win’s own words, or (where he has left us no definite state- ments as to his views) give what he appears to have tacitly assumed or understood.

1 Origin of Species, p. 488. 2 T. H. Huxley: Darwiniana; Essays, I894, p. 14.


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Does mind come into the causal series of organic evolution at large; is it actively concerned in progress, i. e., has it a “survival value?”

To each clause of this question Darwin answers emphati- cally: “Yes.” It is noteworthy, however, that he nowhere formulates, in definite terms, the problem of mind in the causal series of organic evolution, as distinct from the problems of mind’s activity in progress and “survival value.” What he had to say of mind in the one connection is inextricably inter- woven with what he said of it in the others.

The story can be largely told in his own words, and is contained almost entirely in the ” Descent of Man. ”

” Of the high importance of the intellectual faculties, there can be no doubt, for man mainly owes to them his predominant position in the world. We can see, that in the rudest state of society, the indi- viduals who were the most sagacious, who invented and used the best weapons or traps, and who were best able to defend themselves, would rear the greatest number of offspring. The tribes which included the largest number of men thus endowed, would increase in number and supplant other tribes. Numbers depend primarily on the means of subsistence, and this depends partly on the physical nature of the country, but in a much higher degree on the arts which are there practised . … All that we know about savages, or may infer from their traditions . . .. show that from remotest times successful tribes have supplanted other tribes, …. and they succeed mainly, though not exclusively, through their arts, which are products of the intellect. It is, therefore, highly probable that with mankind the intellectual faculties have been mainly and gradually perfected through natural selection . .. Now, if some one man in a tribe, more sagacious than the others, invented a new snare or weapon, or other means of attack or defence, the plainest self interest, without the assistance of much reasoning power, would prompt the other members to imitate him, and all would thus profit.

. If the new invention were an important one the tribe would increase in number, spread and supplant other tribes.”‘

” Man, in the rudest state in which he now exists, is the most dom- inant animal that has ever appeared on this earth. He has spread more widely than any other highly organized form; and all others have yielded before him. He manifestly owes this immense superior- ity to his intellectual faculties, to his social habits, which lead him to aid and defend his fellows, and to his corporal structure. The supreme importance of these characters has been proved by the final arbitrament of the battle for life. Through his powers of intellect, articulate language has been evolved; and on this his wonderful advancement has mainly depended. As Mr. Chauncey Wright remarks, ‘ a psychological analysis of the faculty of language shows, that even the smallest proficiency in it might require more brain

Descent, new ed., pp. I28-9. IX-36


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power than the greatest proficiency in any other direction.’ He has invented and is able to use various weapons, tools, traps, etc., with which he defends himself, kills or catches prey, and otherwise obtains food. He has made rafts or canoes for fishing or crossing over to neighboring fertile islands. He has discovered the art of making fire, by which hard and stringy roots can be rendered digesti- ble, and poisonous roots or herbs innocuous. This discovery of fire, probably the greatest ever made by man, excepting language, dates from before the dawn of history. These several inventions, by which man in the rudest state has become so pre-eminent, are the direct results of the development of his powers of observation, memory, curiosity, imagination and reason. I cannot therefore understand how it is that Mr. Wallace maintains, that ‘natural selection could only have endowed the savage with a brain a little superior to that of an ape.’ ” 1

” . .. The intellect must have been all-important to him even at a very remote period, as enabling him to invent and use lan- guage, to make weapons, tools, traps, etc.,whereby with the aid of his social habits he long ago became the most dominant of all living creatures.”2 …. “But mere bodily strength and size would do little for victory, unless associated with courage, perseverance and determined energy.”

In a letter to Lyell we find these words: “I can see no difficulty in the most intellectual individuals of a species being continually selected; . . . . the less intellectual races being exterminated.” 4

And compare the following: ” Obscure as is the problem of the advance of civilization, we can at

least see that a nation which produced during a lengthened period the greatest number of highly intellectual, energetic, brave, patriotic and benevolent men, would generally prevail over less favored na- tions.” ‘

In another letter, also to Lyell, he answers a case which seems at first sight contrary to his theories, i. e., the stagna- tion and retrogression of the Greeks after having very high intellectual attainments.

“Thinking over . . . . the high state of intellectual develop- ment of the old Grecians with little or no subsequent improvement, being an apparent difficulty, it has just occurred to me that in fact the case harmonizes perfectly with our views …. For in a state of anarchy, or despotism, or bad government, or after irruption of barbarism, force, strength or ferocity and not intellect would be apt to gain the day.”6

In the passage which follows, Darwin carries to its logical conclusion his view of the importance of mind to progress.

Descent, pp. 48-49. Italics mine. 2 Ibid., pp. 609-Io. 3 Ibid., p. 564. 4 Life and Letters, Vol. II, p. 7. 5Descent, p. 142. 6 Life and Letters, Vol. II, pp. 88-9.


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Not only does the individual mind serve the individual man in the struggle for existence, but the collective mind in a com- munity is a necessity for common progress. He writes:

” The presence of a body of well instructed men, who have not to labor for their daily bread, is important to a degree which cannot be overestimated; as all high intellectual work is carried on by them, and on such work material progress of all kinds mainly depends, not to mention other and higher advantages. . . . If in each grade of society the members were divided into two equal bodies, the one in- cluding the intellectually superior and the other the inferior, there can be little doubt that the former would succeed best in all occupa- tions and rear the greater number of children.”‘

The above quotations state clearly and fairly Darwin’s case with regard to man; but he held emphatically that mind in ani- mals was, though in a less degree, still in the same relation to evolution as mind in man.

” In all changes,” he tells us, “whether from persecution or con- venience, intelligence must come into play in some degree. The kitty-wren (I. vulgaris), which builds in various situations, usually makes its nest to match with surrounding objects, but this is perhaps instinct.” 2

“Mr. Swinhoe attributes the victory of the common rat [in the struggle for existence] over the large Mus conniga, to its superior cunning.” 3

” The social instinct is indispensable to some animals, useful to still more, and apparently only pleasant to some few animals.”4

” With those animals which were benefited by living in close asso- ciation, the individuals which took pleasure in society would best escape various dangers; whilst those that cared least for their com- rades and lived solitary would perish in greater numbers.”5

Particularly in his treatment of the evolution of the lower animals does he make a strong case for mind, stated under a quite new aspect. This is his work on ” Sexual Selection ;” for he makes sexual selection from first to last a psychical phe- nomenon, in the plainest sense of the word. Sexual selection means above all choice, and implies the feelings of love, jealousy, pleasure, disgust and dislike, to say nothing of the more dis- tinctly intellectual attainments of observation and discrimina- tion. In dealing with this, Darwin is everywhere explicit. He says, for instance:

” Sexual selection . . . . has played an important part in the history of the organic world.”6 ” Secondary sexual characters . . .

1 Descent, pp. I35-6; cf. the very definite statement on p. 49, and the parallel passages on pp. 93 and 617.

2 Posthumous Essay on Instinct, in G. J. Romanes’s Mental Evolu- tion in Animals, p. 370.

3 Descent, p. 8o. 4 Instinct, p. 381. 5 Descent, p. o05. 6Ibid., p. 6I3.


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in the higher classes have been acquired through sexual selection, which depends on the will, desire and choice of either sex.”l “As far as can be trusted, the conclusion is interesting that sexual selection, together with equal or nearly equal inheritance by both sexes, has indirectly determined the manner of nidification of whole groups of birds.”2

In this last passage he declares that habit is indirectly deter- mined, for a group of birds, by the same agency-sexual selection-which determines structure. It must be observed, however, that sexual selection cannot occur until some degree of intelligence has already been reached in the animal world. In a letter to F. Muller (Feb. 22, [I869?] ), we find this:

” But what I want to know is, how low in the scale sexual differ- ences occur which require some degree of self-consciousness in the males, as weapons by which they fight for the females, or ornaments which attract the opposite sex.”3

Enough has now been quoted to show that Darwin returns an emphatic affirmative to the questions whether or not mind comes into the causal series of organic evolution at large, is actively concerned in progress, and has a survival value. We must now turn to our second question, and see what Darwin understood the term mind to cover.


Unfortunately, we have to note, at the beginning of this Chapter, that Darwin failed to define his terms, and nowhere tells us in so many words what he meant to imply by ” mind. ” After using the word for nearly a life-time, he remarks at the end of his work on Emotions,4 which was distinctly a contri- bution to psychology: “I have often felt much difficulty about the proper application of the terms, will, consciousness, and intention. Actions which were at first voluntary soon become habitual, and at last hereditary, and may then be performed even in opposition to the will. ”

I propose here to give, briefly, what appear to have been his views, and to support my statements by the quotations which seem to prove my conclusions.

If a ball be struck, it will change its position, and move in the direction of the blow; if a piece of ice be laid on a hot surface, it will change its form and condition, and melt; if a drop of acid be placed upon the skin of a brainless frog, a leg is moved toward the acid which is, if possible, wiped away.

Descent, p. 260. 2Ibid.,p. 456. 3 Life and Letters, Vol. II, p. 293. 4 This work was written about 8 years before his death. 5 Emotions, p. 357.


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None of these actions are supposed to be accompanied by consciousness. Now I think that Darwin held distinctly that the movement of the leg of a brainless frog in response to the acid is of quite a different kind from the movement of the struck ball or melting ice; it belongs to an entirely different category of phenomena from the phenomena of the merely mechanical causal series. This is a statement somewhat diffi-

cult of proof; but the following sentence seems at least some small evidence in its favor.

” Reflex actions, in the strict sense of the term, are due to the excitement of a peripheral nerve, which transmits its influence to certain nerve-cells, and there in their turn excite certain muscles or glands into action; and all this may take place without any sensa- tion or consciousness on our part, though often thus accompanied.”l

It is in reflex action, even though it ” takes place without any sensation or consciousness,” that we find the beginning of that something which later is called mind. Not that Darwin held that mind developed out of, or up from, reflex action, for I think the following passage shows that he did not:

” It is scarcely credible that the movements of a headless frog,when it wipes off a drop of acid or other object from its thigh, and which movements are so well co-ordinated for a special purpose, were not at first performed voluntarily, being afterwards rendered easy through long-continued habit so as, at last, to be performed unconsciously, or independently of the cerebral hemispheres:” 2 but reflex action seems to be the line of demarcation between the world of living matter and the world of dead, and is in some way other than the physical forces proper.

Higher than reflex action is instinct, and above instinct comes intelligence. Whether Darwin would have applied the term “mind” unconditionally to instinct is difficult to state, but from the general drift of his whole work it seems to me that, though he distinguished rather sharply between intelli- gence and instinct, he still held instinct to be in some way mind. Certainly he nowhere says it is not mind, even when he writes : “The very essence of an instinct is that it is followed independently of the reason.”8 The following may make this clear:

” Water-hens and swans, which build in or near the water, will in- stinctively raise their nests as soon as they perceive the water begin to rise.”4

He goes on to cite many cases of birds apparently choosing, selecting, and acting from habit and inheritance. He did not

1Emotions, p. 35. 2 Ibid., p. 40. 3 Descent, p. I22. 4lnstinct, p. 370.


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think that intelligence was developed from instinct, for he says in a letter to Asa Gray, of April, I86o:

” The reviewer takes a strange view of instinct: he seems to regard intelligence as a developed instinct, which I believe to be wholly false. I suspect he has never much attended to instinct and the minds of animals, except by reading.”l

That animals had intelligence as well as instinct he firmly believed, though he did not copsider the scope very wide, for he says quite emphatically (also in a letter to Gray): ” The coolness with which he [Bowen] makes all animals to be des- titute of reason is simply absurd.”2 ( Nov. 26, i86o.)

And again, “only a few persons now dispute that animals possess some power of reasoning. Animals may constantly be seen to pause, deliberate and resolve.”8

Regarding the mind of man he held simply that we have here a culmination,-a flowering,-for the whole series of organic species, but not something which differs in essence from the mind of the lower orders.

” The mental faculties of man and the lower animals do not differ in kind, though immensely in degree.”4 “The fact that the lower animals are excited by the same emotions as ourselves is so well established, that it will not be necessary to weary the reader with many details.”8 “As man possesses the same senses as the lower ani- mals his fundamental intuitions must be the same.”6

To the ” high mental powers ” of ” abstraction, general con- ception, self-consciousness, mental individuality,” he devotes a little over one page in the ” Descent of Man.” Here, if any- where in his work, he shows how really little the meaning and value of his psychological terms had appealed to him. For instance, he attributes abstract ideas to some animals, and tells us that ” when a dog sees another dog at a distance it is often clear that he perceives that it is a dog in the abstract [!]; for when he gets nearer his whole manner suddenly changes if the other dog be a friend.”7

As I am to take up the development of instinct later, it will be enough here, in summing up this Chapter, to say that in a broad sense mind is used to cover all those attributes or powers of living beings, reasoning, abstraction, attention, self-con- sciousness, etc., which might be called ” intelligence, ” and those actions and feelings which might be spoken of as ” instinctive.” These two, together with reflex action, Darwin included in a

1 Life and Letters, Vol. II, p. 99. 2 Ibid., Vol. II, p. I46. 3 Descent, p. 75. 4 Ibid., p. I47. 5 Ibid., p. 69. 6 Ibid., p. 66. 7 Ibid., p. 83.

542 CARTER :

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vague, unnamed, undefined group of manifestations differing essentially from the actions and reactions of the inorganic world. He treated intelligence, instinct and reflex action as phenomena of the same general kind, and showed that they were genetically related and subject to the same evolutional laws. It is my belief that he applied the term mind, or would have applied it had he given attention to his meanings and definitions in psychology, to every manifestation occurring in living matter to which any, even the most rudimentary form of consciousness could be ascribed, whether the animal mani- festing it were a single cell or a complex organism; but that in general, he restricted it to what are called the “higher ” mental faculties. In other words, he simply adopted the popu- lar view of mind.


A difficulty strikes us at the very outset of our inquiry into the relation of brain and mind, for Darwin used the two words almost interchangeably. He summed up his views when speaking of the change which came to him in his later life, through the loss of his aesthetic interests. He says: ” My mind seems to have become a kind of machine for grinding

general laws out of large collections of facts, but why this should have caused the atrophy of that part of the brain alone on which the higher tastes depend, I cannot conceive. A man with a mind more highly organized or better constituted than mine would not, I suppose, have thus suffered, and if I had to live my life over again I would have made a rule to read some poetry and listen to some music at least once every week; for perhaps the parts of my brain now atrophied would thus have been kept alive through use.”l

The discovery of the exact views held by Darwin on the relation of mind and brain is a task by no means easy. We have to remember that he never came to close quarters with his problem. That brain is the physical substrate of mind, and a particular brain of a particular mind, he never probably doubted, or even conceived the possibility of its being other- wise; but just what the relation of mind and brain implies, how it is effected, seems to have been equally remote to him. It strikes one with astonishment, in the midst of one’s admira- tion for his stupendous tasks, his infinite care and his devotion to detail, to find this simplicity of view amounting almost to shallowness with regard to one of his fundamental problems,- a problem whose data he was continually collecting and collating, yet whose essence he seems to have missed to the last.

1Life and Letters, Vol. i, pp. 81-82.


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In his work on the ” Expression of the Emotions”‘ he devotes one of his longest, and in some ways, most critical chapters to Blushing, and gives a special section entitled, ” The Nature of the Mental States which Induce Blushing.”‘

“These consist of shyness, shame and modesty; the essential element in all being self-attention. Many reasons can be assigned for believing that originally self-attention directed to personal appearance in relation to the opinion of others was the exciting cause.”

Then follow several pages of citations, and then the follow- ing:

“Finally, then, I conclude that blushing-whether due to shyness -to shame for real crime-to shame from a breach of the laws of etiquette-to modesty from humility-to modesty from indelicacy- depends in all cases on the same principle; this principle being a sensitive regard for the opinion, more particularly for the deprecia- tion of others, primarily in relation to our personal appearance, especially of our faces; and secondarily, through the force of associ- ation and habit, in relation to the opinion of others on our conduct.”2

Notice that he has given strictly psychological causes of blushing. His theory of it, somewhat condensed, I give in his own words; in it he sets forth, as clearly as anywhere in his works, his ideas on the relation of body and mind.

“The hypothesis which appears to me most probable, though it mnay at first seem rash, is that attention closely directed to any part of the body tends to interfere with the ordinary and tonic contraction of the small arteries of that part. These vessels, in consequence, become at such times more or less relaxed, and are instantly filled with arte- rial blood. This tendency will have been much strengthened, if fre- quent attention has been paid during many generations to the same part, owing to nerve-force readily flowing along accustomed channels, and by the power of inheritance. Whenever we believe that others are depreciating or even considering our personal appearance, our attention is vividly directed to the outer and visible parts of our bodies; and of all such parts we are most sensitive about our faces, as no doubt has been the case during many past generations. There- fore, assuming for the moment that the capillary vessels can be acted on by close attention, those of the face will have become eminently susceptible. Through the force of association the same effects will tend to follow whenever we think that others are considering or cen- suring our action or character. As the basis of this theory rests on mental attention having some power to influence the capillary circu- lation, it will be necessary to give a considerable body of details bearing more or less directly on the subject. Several observers [a note gives the authorities], who from their wide experience and knowl- edge are eminently capable of forming a sound judgment, are con- vinced that attention or consciousness (which latter term Sir H. Holland thinks the more explicit) concentrated on almost any part of the body produces some direct physical effect on it. This applies to the movements of the involuntary muscles, and of the voluntary

Emotions, p. 326. 2 Ibid., p. 337.

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muscles when acting involuntarily,- to the secretion of the glands,- to the activity of the senses and sensations,- and even to the nutrition of parts. [Then follow some cases which I omit.] Certain glands are much influenced by thinking of them, or of the conditions under which they have been habitually excited. This is familiar to every one in the increased flow of saliva, when the thought, for instance, of intensely acid fruit is kept before the mind. . We thus see that close attention certainly affects various parts and organs, which are not properly under the control of the will. By what means atten- tion -perhaps the most wonderful of all the wondrous powers of the mind-is affected, is an extremely obscure subject. According to Miiller (Elements of Physiology) the process by which the sensory cells of the brain are rendered, through the will, susceptible of re- ceiving more intense and distinct impressions, is closely analogous to that by which the motor cells are excited to send nerve force to the voluntary muscles …. The manner in which the mind affects the vaso-motor system may be conceived in the following manner: When we actually taste sour fruit, an impression is sent through the gustatory nerves to a certain part of the sensorium; this transmits nerve force to the vaso-motor center, which consequently allows the muscular coats of the small arteries that permeate the salivary glands to relax. Hence more blood flows into the glands, and they secrete a copious supply of saliva. Now it does not seem an improbable assumption, that, when we reflect intently on a sensation, the same part of the sensorium, or a closely connected part of it, is brought into a state of activity, in the same manner as when we actually per- ceive the sensation. If so, the same cells in the brain will be excited, though perhaps in a less degree, by”vividly thinking about a sour taste, as by perceiving it; and they will transmit in the one case as in the other nerve force to the vaso-motor center with the same results. … . .Now as men during endless generations have had their attention often and earnestly directed to their personal appearance, and especially to their faces, any incipient tendency in the facial cap- illaries to be thus affected will have become in the course of time greatly strengthened through the principles just referred to, namely: nerve force passing readily along accustomed channels, and inherited habit. Thus, as it appears to me, a plausible explanation is afforded of the leading phenomena connected with the act of blushing.” 1

I may pause here a moment to point out a concrete illustra- tion of what I have called Darwin’s simplicity of view almost amounting to shallowness; in this work he constantly uses (I believe for the first time, for I have failed to notice even one in- stance of it in his earlier works) the term ” nerve force. ” He speaks of the undirected flow of nerve force, and the undirected ,overflow of nerve force, 2 the steady flow of nerve force ,8 the involuntary transmission of nerve force,-4 radiation of nerve force,5 and a thrill of nerve force,6-yet nowhere does he make an attempt to tell us what this nerve force is, how it is related

1 Emotions, pp. 337-344. 2 Ibid., pp. 32 and 349. 3 Ibid., p. 71. 4 Ibid., p. 68. 5 Ibid., p. 41. 6 Ibid., p. I97.


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to or compares with other known physical forces; how it “flows,” “overflows,” “radiates” and “thrills,” and, above all, what is its significance for consciousness. That it had significance for consciousness to his mind, will, I think, be evident from the context of two or three of the phrases quoted:

“The frantic and senseless actions of an enraged man may be attrib- uted in part to the undirected flow of nerve force, and in part to the effects of habit.”1

” This involuntary transmission of nerve force may or may not be accompanied by consciousness. Why the irritation of a nerve cell should generate or liberate nerve force is not known, but that this is the case seems to be the conclusion arrived at by all the greatest physiologists. “2

“On the other hand many of the effects due to the excitement of the nervous system seem quite independent of the flow of nerve force along the channels which have been rendered habitual by former exer- tions of the will; . . . . for instance, the change of color in the hair from extreme terror or grief,-the cold sweat and the trembling of the muscles from fear.”3

The above quotations bring out the point I made earlier, that Darwin had thought widely but not deeply upon psycho- logical subjects, and that he never came to close quarters with some of his fundamental problems. He gives the facts clearly enough, but makes no attempt to reason them out to their legitimate conclusions. He tells us of nerve force producing action on the vaso-motor center, of undirected nerve force (in part) producing “frantic and senseless actions;” of an “in- voluntary transmission of nerve force ” accompanied or not accompanied by consciousness; and last, but not least, of still other effects due to the nervous system, but independent of nerve force.

It may be urged that Darwin used the terms current in his day, which he obtained from the literature his quotations show him to have been familiar with. This, it seems to me, only emphasizes the fact that his psychology was at best second- hand, and that his contributions to philosophy did not lie in the exposition of the phenomena of consciousness in more than a superficial sense.

If Darwin did not define what he meant by nerve force, still less did he trouble himself with a clear statement of what he considered the exact relation of mind and brain to be. I have already quoted passages from his letters and works to show that he used the terms brain and mind interchangeably; I add one now, which occurs in the Descent of Man, and seems to me to carry more weight than the others :

1 Emotions, p. 349. 2 Ibid., p. 71. 3 Ibid., p. 50.


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“As soon as the mental faculties had become highly developed, images of all past actions and motives would be incessantly passing through the brain of each individual. . . . As past impressions were compared during their incessant passage through the mind,” etc.1

In spite of these quotations it is difficult to believe that he considered the brain and mind as one and the same thing,- that the mind is the brain,-but I do think that he looked upon the mind as in the brain (he speaks of the ” frontal part of the skull” as the seat of intellectual faculties)2 in some way, and conditioned by it; yet at the same time he speaks of ” the increased size of the brain from greater intellectual develop- ment,”3–indicating that the brain was, on the other hand, conditioned by the mind.

The further manner of the relation of brain and mind was by interaction. The substance of his theory of blushing is that we have a bodily action caused by a mental one, a psychic state causing a physical response. If his explana- tion leaves anything to be desired in explicitness it is offset by this passage, in which he states that the mind affects the heart.

” Hence when the mind is strongly excited, we might expect that it would instantly affect, in a direct manner, the heart; and this is universally acknowledged and felt to be the case. Claude Bernard also repeatedly insists, and this deserves special notice, that when the heart is affected it reacts on the brain; and the state of the brain again reacts through the pneumo-gastric nerve on the heart; so that under any excitement there will be much mutual action and reaction between these two most important organs of the body.”4

” So a man may intensely hate another, but until his bodily frame is affected he cannot be said to be enraged.”5

” He who gives way to violent gestures will increase his rage; he who does not control the signs of fear will experience fear in a greater degree; and he who remains passive when overwhelmed with grief loses his best chance of recovering elasticity of mind. These results follow partly from the intimate relation which exists between almost all the emotions and their outward manifestation; and partly from the direct influence of exertion on the heart, and consequently on the brain. Even the simulation of an emotion tends to arouse it in our minds.”6

In the first of these quotations he states that mind acts on heart, and heart reacts on brain; but if we assume that ” mind”‘ was meant in the second instance, we can safely say that he commits himself to an interaction theory of mind and body.

1 Descent, pp. 98 and Ioo. 21bid., p. 55. 3 Ibid., p. I97. 4Emotions, pp. 68-9. Italics mine. 5 Ibid., p. 240. 6 Ibid., p. 366.


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It is not impossible that he looked upon mind as a function of brain, though there is very little in his works to indicate this. In his book on the Emotions he quotes from Dr. Mauds- ley’s ” Body and Mind,” in this passage:

“He adds, that as every human brain passes, in the course of its development, through the same stages as those occurring in the lower vertebrate animals, and as the brain of an idiot is in an arrested condition, we may presume that it ‘ will manifest its most primitive functions, and no higher functions.’ “1

Still we must not lay too much stress upon this paragraph. While we are dealing with the views which Darwin held

upon the relation of mind and brain, it may not be without interest to note that he never seriously entertained the concept of mind as a secretion of brain,-in fact he does not even mention the theory. That it was familiar to him we may justly infer because he quotes frequently from the materialistic literature of the time,-Carl Vogt and others,-in which the subject was either treated or touched upon. The fact that he never thought it worth refuting would seem to indicate that the idea of brain and mind as two distinct yet interacting entities was too firmly grounded in him to admit the consider- ation of any rival theories. The expression he quotes from Maudsley about ” brain manifesting its primitive functions,” may have meant no more to him than ” manifesting those conditions or states along with which, or under which, consciousness of various kinds occurs”.

Taking, then, what he actually said about interaction of brain and mind, and what he failed to say about other theories, -mind as a function or as a secretion of brain,-we may state in answer to the question: How are mind and brain related ? that Darwin postulated two distinct, interacting interdependent realities, Mind and Brain.


We come now to the main problem of our inquiry -what Darwin understood by Mental Development. We already have in hand some of our chief material. We have seen that Darwin held mind to be actively concerned in progress and causally related to organic evolution at large; that by mind he meant not only the higher faculties, but instinct, and that he considered the relation of mind to body to be one of inter- action.

It is not in any way within the scope of this paper to show how, given Darwin’s data for organic evolution, they would work out under any of the current theories of the relation of

1Emotions, p. 246. Italics mine.

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