An Introduction to Comparative Psychology
Chapter 3: Other Minds than Ours
C. Lloyd Morgan
A DISTINGUISHING feature of modern psychology is the employment of the comparative method. So long as the psychologist restricts himself to the introspective study of the workings of his own consciousness, his conclusions rest on a basis which, however sure it may appear to himself, must be limited by the inevitable restrictions of his own individuality. When he compares and correlates his own results with those of other introspective observers, he becomes so far a comparative psychologist, and by widening his basis renders his conclusions more comprehensive. A further stage of the comparative method is reached, when he endeavours to correlate the results of introspective psychology with the conclusions reached by the physiological study of those nervous processes which are the concomitants of psychical states. On the hypothesis of monism, he is thus comparing two wholly different aspects of the same natural occurrences; on the hypothesis of dualism, two wholly different occurrences, which are nevertheless invariably associated. In any case, by proceeding to this comparison, he links his subject with the science of biology in a way that has proved eminently helpful to his own branch of study. Now, the keynote of modern biology is evolution ; and on the hypothesis of scientific monism here adopted, though not necessarily on that of empirical dualism, we are not only logically justified in extending our comparative psychology so as to include within its scope the field of zoological psychology, but we are logically bound to regard
(37) psychological evolution as strictly coordinate ate 'with biological evolution.
I propose to consider in this chapter what we can know of other minds than ours, and how we may gain this knowledge. It follows from what has just been said, that since biological evolution has given rise to individuals of diver: gent types of organic structure, there may be-nay, there must be-in these divergent biological individuals divergent types of mind, using the word " mind " in the widest and most comprehensive sense as embracing all modes of psychical activity. The question arises, however, how we are to gain acquaintance with these divergent types of mind. And here we are met by the fundamental difficulty which comparative psychology, both human and zoological, encounters when it leaves the broad field of general considerations, to enter upon the more particular study of individual and concrete cases with divergent possibilities of interpretation. For we have direct and immediate acquaintance with no other psychical processes than those which we can study by the introspective method in ourselves. Hence introspective study must inevitably be the basis and foundation of all comparative psychology.
I will endeavour to illustrate the fundamental difficulty of comparative psychology by means of an analogy. Suppose that a chronometer were gifted with intelligence and reason, and were to enter upon the study of other timepieces all access to their works being inexorably denied it. It would be able to observe the motions of the hands over the dial-plate, and perhaps gain some information by attentively listening to the internal sounds. But when it came to the interpretation of these observed phenomena, and when itattempted to explain their inner causes, the chronometer would be forced to frame all such interpretation and such explanation in terms of its own works. With no other works would it have any acquaintance. It would infer, and
(38) justly infer under the circumstances, that the works of other timepieces were, on the whole, of like nature with those which actuated the movements of its own hands over the dialface. There can be no question, moreover, that the more thorough and accurate the acquaintance of the chronometer with its own works, the more valid would be its inferences with regard to the hidden works of other timepieces. For example, it might learn by introspection that it possessed a mechanism of compensation for changes of temperature; and noticing that in other timepieces the rate of movement of the bands varied with the rise or fall of the thermometer, it might infer that in them such mechanism was absent. It is probable, however, that the chronometer would interpret all the phenomena as due to the action of a mainspring, since it would necessarily be unacquainted with the impelling motive power derived from the descent of heavy weights; and the outflow of energy from the spring would, in its interpretation, be regulated by some sort of balance-wheel, since the principle of the pendulum would nowhere be found through introspection of its works. Thus there would be for the chronometer inevitable possibilities of error. And although it could do little more than speculate concerning these possibilities, it would certainly be wise in refraining from anything like dogmatism concerning the insides of other timepieces which it must interpret, if it interpret at all, in terms of its own chronometer works, but which might not impossibly, could it only get at them, exhibit the application of other mechanical principles.
Now this analogy must certainly not be pressed too far, it is, here adduced to illustrate the fact that just as the supposed chronometer would be forced to interpret the mechanism of other timepieces in terms of its own mechanism, so man is forced to interpret the psychology of animals in terms of human psychology, since with this alone he has first - hand acquaintance through the study of the
(39) nature and sequence of his own mental processes. But it will perhaps be said that the analogy is invalidated on the principles I have myself adopted, by the fact that in animals a knowledge of the organic mechanism, the functional activity of which is the objective aspect or correlate of psychical processes, is not beyond our reach, but is attainable through physiological research. Access to the works of other timepieces, at any rate from the objective side, is, it may be said, not inexorably denied to man' the investigating chronometer. So far from this being the case, it is the comparative study of other " works," taken in connection with the comparative study of the life-activities effected through their means, that affords the justification of inferential conclusions concerning the psychical processes of animals. This view of the matter, in which I concur, does not seem to me wholly to invalidate the chronometer analogy ; but it does suggest a modification, and further development of the analogy.
The chronometer, we will suppose, is acquainted through introspection with its own psychology, and is able to take to pieces the works of other timepieces. It finds a number of chronometers whose works are all practically identical, and as it believes, but cannot demonstrate without taking itself to pieces, just like its own; and it is led to the inference that their psychology is similar to its own. It finds also a number of other timepices (sic) whose works are constructed on similar principles, and differ chiefly in their being less highly finished and somewhat less complex; and it is led to the inference that their psychology, though less developed and less complex: than its own, has probably been evolved on similar lines. But when it comes to the kitchen clock, it finds certain general similarities, cog-wheels and chains and so forth, but it also discovers principles of construction so different, the weights and the pendulum being so unlike its own balance-wheel and escapement, that it hesitates to
(40) draw any positive and definite conclusions. It sees that though the psychology of the kitchen clock may be closely analogous to its own, it may be quite different. It refuses to express a definite opinion on the psychology of the kitchen clock.
To apply the analogy in this modified form. Man, by anatomical and physiological research, has found in other men cerebral hemispheres with sensory-centres, control-centres, and so forth, similar to those which he believes that he individually possesses; and he infers that their psychology is of like nature to his own. He also finds in other vertebrates cerebral hemispheres, with sensory-centres and so forth, differing from man's chiefly in mass and complexity; and he infers that their psychology, though less developed and less complex than his own, has probably been evolved on similar lines. But when lie comes to the insect, the crustacean, the mollusc, not to mention the worms, the seaanemone, or the amoeba he finds nervous systems so different in types of structure from his own, that he hesitates to draw any definite and positive conclusions concerning the psychical states of these animals. It is true that there are nerve-fibres and nerve-cells; but the manner of their arrangement is so different from that of the vertebrates to which he belongs, that the careful student of zoological psychology is forced to conclude, that though the psychical states of insects and crustacea may be similar to those of man, they may be markedly dissimilar.
It may indeed be contended that community of environment-the joint-tenancy of the same world -- must necessarily beget community of psychical faculty to meet the requirements of that - environment. But while admitting the soundness of this argument so far as it goes, I venture to submit that it does not go far. For why should the community of psychical nature be greater than that of physical nature? The anatomy or the physiology of insects, for
(41) example, differs tolerably widely from that of man - why then should he suppose that their psychical endowments are more closely similar? Both physical nature and psychical nature are so to speak moulded in accordance with the environment. To both the argument of a joint-tenancy of the world applies. The physical nature being widely divergent from that of man, is it not reasonable to suppose that the psychical nature is, or at least maybe, also widely divergent ?
No one can study with any attention and care the habits and activities of such insects as ants and bees, without feeling convinced that they profit by experience and that their actions are under control. It is true that at present we know little about the physiology of this control, and of the relation of control centres to automatic centres. But this may sooner or later be remedied by an extension of our knowledge of the nerve-physiology of insects. I am the last to think of counselling any abatement of zeal in the fascinating study of the activities, and of the minute anatomy and physiology of the higher invertebrate forms of life. But I am of opinion that students in this department of investigation may do well to lay to heart the, less on conveyed by the analogy of the chronometer and the kitchen clock. In any case, in an introduction to comparative psychology, I feel bound to lay stress on the necessity for the greatest caution in the psychical interpretation of insect activities; and I feel justifii!d in restricting myself, in this work, to a consideration of the psychical states which we may infer to be associated with the- functional activity of the cerebral hemispheres in the higher vertebrates.
Now it is clear that the validity of our inferences concerning the mental processes which underlie the actions of our human neighbour, is primarily dependent on the similarity of his mind to our mind. If he is an Englishman, of the same social grade as ourselves, of like tastes and habits of
(42) thought, educated under the same school system, the similarity will be fairly close, though even here there must be slight individual differences. But if he be a foreigner, of a different social grade from ours, differing from us in tastes and habits of thought, educated on other school systems than ours, there will be a wide margin of dissimilarity. We shall find no little difficulty in putting ourselves in his place, in understanding how with such and such facts staring him in the face he can hold the views he says he holds, and in conceiving how he can derive any pleasure from that which would bore us to death, or would set our aesthetic teeth on edge, or would painfully shock our moral sensibility. In dealing with North Australians, or Maori or South Sea Islanders or Red Indians, our difficulties are proportionally increased. These are peoples who have been living, generation after generation, under circumstances widely different from those in which our own race has been nurtured. How difficult it is justly to interpret their thoughts and feelings, and to reach the mental processes which are the psychical accompaniments of their actions, to us so strange and meaningless! And the difficulty is due to the fact, that the only mind with which we can claim any first-hand acquaintance is the civilised mind, that of which we are conscious within ourselves. In the terms of this mind, that of the aboriginal Australian or Red Indian has to be interpreted. We must remember that among civilized men careful introspection and comparative study have led to the formation and adoption of tolerably clean-cut and self-consistent views of the world, and of our relations as individuals to that which we regard as universal. But among primitive folk, of less introspective and reflective power, we must not expect such definiteness and self-consistency. And I confess that I read with some scepticism much that is written on the animistic or fetishistic or other interpretations which are read by philosophers into the vague and often contradictory
(43) beliefs of uncivilized peoples. It is difficult for us to realize with what content such peoples can 'hold a number of beliefs which to us appear self-contradictory, and how readily they are satisfied with isolated fragments of explanation, having little or no desire to combine them into a consistent whole. Again, in our very midst there are beings, so like us, and yet so different, the understanding of whose mental processes is difficult and yet most important. I refer to our own children. How unexpected are often the actions of children! How strange their whims and moods and fancies! How charmingly illogical and irrational they sometimes are, and yet often how surprisingly sharp and clever! Notwithstanding the excellent work that has been done in this branch of study, the psychology of the child is a field in, which much careful observation and much cautious inference is still needed. And why are the difficulties of interpretation so great? Because we have to interpret in terms of the adult-mind the child-mind, in which the relative development of the faculties, like the relative development of the bodily organs, is so different from that of men and women. It is true that we ourselves have once been children. But what most of us remember of our child-days is not the nature of our mental processes, but certain salient products. A greater or less number of striking external incidents, a few occasions of keen joy or bitter sorrow, constitute for most of us the sum-total of our memories of childhood. To reach mental processes needs introspection, and few children have the power of introspection, or the knowledge by which such introspection must be guided. We have no recollection of the mental processes of childhood, because those mental processes could not then for most of us be objects of thought and contemplation.
Even in human psychology, therefore, if we include not only the psychology of sages, but of ordinary folk, of savages, and of children, there are serious difficulties of
(44) interpretation, Since the validity of our inferences concerning the mental processes which underlie the actions of our neighbour is primarily dependent on the similarity of his mind to our mind, it is clear that, if through divergence of development, or imperfection of development, his mind has come to differ from ours, the validity of our inferences will be so far impaired. For we cannot get at his mind directly; our inferences must always be, for better for worse, in terms of our own mental processes.
It will thus be seen that in studying other minds through their objective manifestations, it is primarily essential that we should have, so far as is possible, a thorough and accurate acquaintance with the only mind we call study at first-hand and directly, namely our own. Without this, anything like scientific interpretation is manifestly impossible~ All rational human beings have, however, some acquaintance with the workings of their own consciousness. And many of those who are not professed psychologists have, through unusual powers of introspection and keen insight, reached conclusions which are just and true, though they are apt to be somewhat lacking in balance. Psychologists make, or should make, no claim to any monopoly of knowledge in the subject they study; their province is mainly to systematise that knowledge. They bear to the acute and accurate observer the relation of the trained biologist to the amateur naturalist. And just as the amateur naturalist is apt to regard the scientific biologist with some suspicion, as one who is over-subtle, and relies too much on the delicate methods of the laboratory and the dissecting-table -- so is the plain mail of shrewd insight apt to regard the psychologist also with some suspicion, as one who is over-subtle in his distinctions, too introspective, and not sufficiently objective in his - study of mind. And the psychologist should accept the criticism, not with impatience and the assumption of all air of superior knowledge and
(45) wisdom, but with a quiet determination to justify his procedure by the results which, through its means, he, is enabled to reach. From the position that the first duty of a psychologist is to attain accurate and systematic acquaintance with the workings of his own mind as tile cipher in terms of which all other minds must be read, lie cannot recede without abandoning the only basis of scientific method possible under the circumstances of the case.
With this as a basis, he may proceed to the so-called objective study of mind-that is to say, to the study of the objective manifestations in other beings of a consciousness more or less similar to that of which he has, through introspection, some first-hand knowledge; his aim being, by such study, to reach an inferential or second-hand knowledge of the nature of the consciousness which actuates the conduct of these beings. And here the student of human psychology is in a position of great advantage, as compared with that which the student of zoological psychology must rest content with. For, by means of specialized objective manifestations, especially of language, self-conscious human beings can signify to each other the nature of their individual conscious experience. Objective manifestations of some kind are the only index we have of the inner psychical experience. But by means of a common language, human beings can purposely set the index, so as to suggest the particular nature of this psychical experience.
Let us revert once more for a moment to the analogy of the chronometer. In two similar chronometers the position of the index-hands at any moment indicates the exact configuration of the wheels of the internal mechanism. Either of these two, then, which knew from introspection the psychical aspect of its own inner processes, would be able to infer with accuracy the exact configuration of the wheels of its neighbour's works from the position of the index-hands. If it had also a pair of subsidiary hands which it
(46) could shift at will, it would be able to indicate at any moment to its neighbour the particular configuration of some previous moment. Thus each could gain inferentially and indirectly through the objective study of the index-hands an accurate knowledge of its neighbour's inner mechanism. Everything, however, would depend upon the similarity of the internal mechanism in the two chronometers. If they were slightly different, they would have very great difficulty in conveying to each other the nature of this difference. So too with human beings. In so far as men are similar in psychical endowments, they can convey to each other through the index of language the nature of their psychical experience. They have great difficulty in making each other acquainted with their individual differences. And the difficulty is the greater the more these individual differences are qualitative, and not merely quantitative., Among civilized men, of like social grade, and somewhat similarly educated, the individual differences are mainly quantitative, -that is to say, differences in the relative development of similar faculties. Careful objective study enables us to gauge and assign a value to the ratio of the faculties in our friends and neighbours. But in the study of uncivilized men, not only of I different social grade, but living under a different social system, men whose education and upbringing has been far other than those under which our own character has been moulded, we find differences which are not merely quantitative but qualitative. There is not merely a difference in the ratio of similar faculties, but a greater or less divergence in the nature of the faculties themselves. It, such cases our inferences are much more difficult and much less trustworthy.
The realization of the difficulties inseparable from the subject, and of his liability to error in the interpretation of the facts, does not, however, deter the student of human psychology from a careful investigation of the objective
(47) manifestations of mind. He takes every opportunity of studying these manifestations, not only in normal men and women of -all grades and of all races, not only in normal children and infants, but in pathological cases in hospitals and asylums, and under those abnormal conditions which are presented by patients in the somnambulistic or hypnotic state. Throughout the whole of these objective investigations, the wise and cautious student never forgets that the interpretation of the facts in psychical terms is based upon the inductions lie has reached through introspection. The facts are objective phenomena; the interpretation is in terms of subjective experience ; and no one has or can have any subjective experience other than that afforded by his own consciousness.
We are now In a position to see clearly what is the distinctive peculiarity of the study of mind in beings other than our own individual selves. Its conclusions are reached not by a singly inductive process, as in Chemistry or Physics, in Astronomy, Geology, Biology, Or other purely objective science, but by a doubly inductive process. Inductions reached through the objective study of certain physical manifestations have to be interpreted in terms of inductions reached through the introspective study of mental processes. By induction I mean the observation of. facts, the framing of hypotheses to comprise the facts, and the verification of the hypotheses by constant reversion to the touchstone of fact. Our conclusions concerning the mental processes of beings other than our own individual selves are, I repeat, based on a two-fold induction. First the psychologist has to reach, through induction, the laws of mind as revealed to him in his own conscious experience. Here the, facts to be studied are facts of consciousness, known at first-hand to him alone among mortals; the hypotheses may logically suggest themselves, in which case they are original so far as the observer himself is concerned,
(48) or they may be, derived,-- that is to say, suggested to the observer by other observers ; the verification of the hypotheses is again purely subjective,' original or derived theories being submitted to the touchstone of individual experience. This is the one inductive process. The other is more objective. The facts to be observed are external phenomena, physical occurrences in the objective world; the hypotheses again may be either original or derived; the verification is. objective, original or derived theories being submitted to tile touchstone of observable phenomena.
Both inductions, subjective and objective, are necessary. Neither can be omitted without renouncing the scientific method. And then finally the objective manifestations in
(49) conduct and activity have to be interpreted in terms of subjective experience. The inductions reached by the one method have to he explained in the light of inductions reached by the other method.
I am anxious to make this matter quite clear, and I will therefore endeavour to illustrate it diagrammatically. In the first diagram (Fig. 7) the line a b represents the conduct, activities, and other objective phenomena exhibited by other beings or organisms than the individual psychologist, while c d represents the states of consciousness of which he alone has direct knowledge.
Then the diagram is intended to show how the psychologist must combine both objective induction and subjective induction, that he may reach a subjective interpretation of a b in terms of c d.
In the second diagram (Fig. 8) the curve represents the living beings under investigation comprising the psychologist himself and other organisms. The upper line represents tile physical objective aspect, the lower line the psychical subjective aspect. The whole of the upper line is open to, the inductive investigation of the psychologist. But of the lower line only the firm part, that representing his own inner consciousness, is open to his- inductive study. The dotted part, that representing the mental side of other organisms, has to be interpreted by the inferential prolongation of the known part of the curve, or, in other words, has to be inter-
(50) -preted in terms of the Subjective inductions reached through introspection.
Now it is idle to assert that one set of inductions is more important than the other, since' both are essential. But there can be no question that the subjective inductions are in some respect more subtle and difficult and delicate than the induction-, concerning objective phenomena. There can be no question that false assumptions and vague generalizations, more commonly pass muster with regard to mental processes than with regard to their physical manifestations. And there can be no question that in the systematic training of the comparative psychologist the subjective aspect is not less important than the objective aspect.
The question now arises whether in passing from human to animal psychology any other method of interpretation is possible than that which holds good for the former. Can the zoological psychologist afford to dispense with that systematic training in introspective or subjective analysis and induction which is absolutely essential for the student of human psychology ? I venture to *contend that he cannot. The scheme of interpretation exhibited diagrammatically in -Fig. 7 holds good I maintain as well for animal psychology as for the psychology of man. There are, I am well aware, many people who fancy that by the objective study of animal life they can pass by direct induction to conclusions concerning the psychical faculties of animal& But this is, I think, through ignorance of the methods of psychology ; or perhaps one may say, without injustice, through ignorance of the method that they themselves unconsciously adopt. All that is necessary, these people will tell you, is to observe carefully, and to explain the actions you observe in. the most natural manner. " In the most natural manner," here means and is equivalent to, in just the same way as you explain the actions of your human neighbours and acquaintances. And these human actions
(51) are explained on the assumption that your neighbour is actuated by motives and impulses similar. to your own. bus these observers who think that their explanations are reached by direct induction are really proceeding unconsciously on the method they affect to disregard. Reduced its logical basis their contention is that the thorough and systematic study of that mind in terms of which they unconsciously interpret all other minds is unnecessary if not misleading.
Now it appears to me that the foundation of this erroneous view, for as such I must regard it, is the tacit assumption that what suffices for practical purposes suffices also for scientific purposes, All fairly successful men and women acquire, and must acquire, a knowledge of human nature sufficient for the practical needs of everyday life under social conditions. Over-subtlety and refinement of analysis, too eat nicety of interpretation, are rather disadvantageous ban otherwise in the practical conduct of affairs. Hence practical men are wont to look with some suspicion at the psychologist as one who is prone to be a mere theorist. In the same way practical politicians not uncommonly look with suspicion on sociologists and political economists, practical engineers regard with similar eyes the subtler theories of the physicist, practical metallurgists look askance on the more delicate methods and more advanced hypotheses of the chemist, and in general the practical man is inclined to ,Utilize the results of the man of science but to regard his ore refined interpretations of natural phenomena as mere theory.
There can be no question that the interpretation of the actions of animals as the outcome of mental processes essentially similar to those of man amply suffices for practical needs. The farmer, the keeper of a kennel, the cattle-breeder, the gamekeeper, the breaker-in of horses, all the .practical men who are employed in the breeding, rearing,
(52) and training of animals, and the great number of people who keep animals as pets or in domestic service find a somewhat rough and ready interpretation amply sufficient for their purposes in hand. And not unnaturally they are surprised that the explanation which suffices for them with their wide practical experience is found by the man of science to need serious revision and correction. Often unacquainted wit h the methods and aims of science in its intellectual aspect -as endeavouring to interpret the phenomena of nature, often regarding science as the generally unpaid servant of practical utility, they smile if they do not sneer, at the arrogance of the man of science who tells them that the explanation which is good enough for tile practical purposes of daily life is not sufficient for the more subtle and refined purposes of scientific interpretation. Be this as it may, I venture to affirm that whereas the man who has to deal with animals for practical purposes can afford to be ignorant of psychological methods and results, the man who would deal scientifically with the psychical faculties of animals cannot afford to be thus ignorant. For the practical man accuracy of observation and careful induction therefrom are of primary importance, validity of psychological interpretation being for him altogether subsidiary. But for the scientific investigator thorough and accurate knowledge of and training in psychology is of at least co-ordinate importance with accuracy of objective observation.
Unfortunately many able men who are eminently fitted to make and record exact observations on the habits and activities of animals have not undergone the training necessary to enable them to deal with the psychological aspect of the question. The skilled naturalist or biologist is seldom also skilled in psychological analysis. Notwithstanding standing therefore the admirable and invaluable observations of our great naturalists, we cannot help feeling that their psychological conclusions are hardly on the same level as
(53) that reached by their conclusions in the purely biological field.
For in the study of animal psychology as a branch of scientific inquiry, it is necessary that accurate observation, and a sound knowledge of the biological relationships of animals, should go hand in hand with a thorough appreciation of the methods and results of modern psychology.
The only fruitful method of procedure is the interpretation of facts observed with due care in the light- of sound psychological principles.
What some of these principles are we have considered, or shall consider, in this work. There is one basal principle, however, the brief exposition of which may fitly bring to a -close this chapter. It may be thus stated :-In no case may we interpret an action as the outcome of the exercise of a higher psychical faculty, if it can be interpreted as the outcome of the exercise of on which stands lower in the psychological scale.
To this principle several objections, none of them however .of any real weight, may be raised. First there is the sentimental objection that it is ungenerous to the animal. In dealing with one's fellow-man it is ungenerous to impute to him lower motives for his actions when they may have been dictated by higher motives. - Why should we adopt a different course with the poor dumb animal from that which we should adopt with our human neighbour ? In the first place, it may be replied, this objection starts by assuming the very point to be proved. The scientific problem is to ascertain the limits of animal psychology. To assume that given action may be the outcome of the exercise of either higher or a lower faculty, and that it is more generous to adopt the former alternative, is to assume the existence of the higher faculty, which has to be proved. In the case of our neighbours we have good grounds for knowing that such and such a deed may have been dictated by either a
(54) higher or a lower motive. If we had equally good grounds for knowing that the animal was possessed of both higher and lower faculties, the scientific problem would have been solved; and the attribution of the one or the other, in any particular case, would be a purely individual matter of comparatively little general moment. In the second place, this generosity, though eminently desirable in the relations of practical social life, is not precisely the attitude which a critical scientific inquiry demands. Moreover, an ungenerous interpretation of one's neighbour's actions may lead one to express an unjust estimate of his moral character and thus to do him grave social wrong; but an ungenerous interpretation of the faculties of animals can hardly be said to be open to like practical consequences.
A second objection is, that by adopting the principle in question we may be shutting our eyes to the simplest explanation of the phenomena. Is it not simpler to explain the higher activities of animals as the direct outcome of reason or intellectual thought, than to explain them as the complex results of mere intelligence or practical sense experience ? Undoubtedly it may in many cases seem simpler. It is the apparent simplicity of the explanation that leads many people naively to adopt it. But surely the simplicity of an explanation is no necessary criterion of its truth. The explanation of the genesis of the -organic world by direct creative fiat, is far simpler than the explanation of its genesis through the indirect method of evolution. The explanation of instinct and early phases of intelligence as due to inherited habit, individually acquired, is undoubtedly, simpler than the explanation which Dr. Weismann would substitute for it. The formation of the canon of the Colorado by a sudden rift in the earth's crust, similar to those which opened during the Calabrian earthquakes, is simpler than its formation by the fretting of the stream during long ages under varying meteorological conditions.
In these cases and in many others the simplest explanation is not the one accepted by science. Moreover, the simplicity of the explanation of the phenomena of animal activity as the result of intellectual processes, can only be adopted on the assumption of a correlative complexity in the mental nature of the animal as agent. And to assume this complexity of mental nature on grounds other than those of sound induction, is to depart from the methods of scientific procedure.
But what, it may be asked, is the logical basis upon which this principle is founded? If it be true that the animal mind can only be interpreted in the light of our knowledge of human mind, why should we not use this method of interpretation freely, frankly, and fully? Is there not some contradiction in refusing to do so ? For, first, it is contended that we must use the human mind as a key by which to read the brute mind, and then it is contended that this key must be applied with a difference. If we apply the key at all, should we not apply it without reservation ?
This criticism might be valid if we were considering the question apart from evolution. Here evolution is postulated. The problem is this: (1) Given a, number of divergently ascending grades of organisms, with divergently increasing complexity of organic structure and correlated activities; (2) granted that associated with the increasing organic complexity there is increasing mental or psychical complexity; (3) granted that in man the organic complexity, the complexity of correlated activities, and the 'associated mental or psychical complexity, has reached the maximum as yet attained; (4) to gauge the psychical level to which any organism has been evolved. As we have already seen,, we are forced, as men, to gauge the psychical level of the animal in terms of the only mind of which we have first-hand knowledge, namely the human mind. But how are we to apply the gauge?
There would appear to be three possible methods, which are exemplified in Fig. 9. Let a represent the psychical stature of man, and 1, 2, 3, ascending faculties or stadia in mental development. Let b c represent two animals the psychical stature of each or which is to be gauged. It may be gauged first by the "method of levels," according to which the faculties or stadia are of constant value. In the diagram, 1, has not quite reached the level of the beginning of the third or highest faculty, while a has only just entered upon the second stadium. Secondly, it may be gauged by the " method of uniform reduction." In both b and c we have all three faculties represented in the same ratio as in a, but all uniformly reduced. And thirdly, it may be gauged by the " method of variation," according to which any one of the faculties 1, 2, or 3, may in b and c be either increased or reduced relatively to its development in a. Let us suppose, for example, that b represents the psychical stature of the dog. Then, according to the interpretation on the method of levels, he possesses the lowest faculty (i) in the same degree as man; in the faculty (2) he somewhat falls short of man ; while in the highest faculty (3) he is altogether wanting. According to the interpretation on the method of uniform reduction he possesses all the faculties of man but in a reduced degree. And according to the interpretation on the method of variation he excels man in the lowest faculty, while the other two faculties are both reduced but in different degrees. The three "faculties" 1, 2, 3, are not here intended to serve any other purpose than merely to illustrate the three methods of interpretation.
On the principles of evolution we should unquestionably expect that those mental faculties which could give decisive advantage in the struggle for existence would be developed in strict accordance with the divergent conditions of life. Hence it is the third method, which I have termed the method of variation, which we should expect a priori to
(58) accord most nearly with observed facts. And so far as we can judge from objective observation (the only observation open to us) this would appear to be the case. Presumably there are few observers of animal habit and intelligence who would hesitate in adopting the method of variation as the most probable mode of interpretation. But note that while it is the most probable it is also the most difficult mode of interpretation. According to the method of levels the dog is just like me, without my higher faculties. According to the method of uniform reduction he is just like me, only nowise so highly developed. But according to the method of variation there are many possibilities of error in estimating the amount of such variation. Of the three methods that of variation is the least anthropomorphic, and therefore the most difficult.
In the diagram by which the method of variation is illustrated, the highest faculty 3 is in c reduced to zero,--in other words, is absent. It may, however, be objected that this is contrary to the principles of evolution, since the presence of any faculty in higher types involves the germ of this faculty in lower types. This criticism only holds good, however, on the assumption that the evolution of higher faculties out of lower faculties is impossible. Those evolutionists who accept this assumption as valid are logically bound to believe either (1) that all forms of animal life from the amoeba upwards have all the faculties of man, only reduced in degree and range, and to interpret all animal psychology on a method of reduction (though nut necessarily uniform reduction), or (2) that in the higher forms of life the introduction of the higher faculties has been effected by some means other than that of natural evolution. I am not prepared to accept the assumption as valid; and it will be part of my task in future chapters to consider how the transition from certain lower to certain higher phases of mental development may have been effected.
(59) If this be so it is clear that any animal may be at a stage where certain higher faculties have not yet been evolved from their lower precursors; and hence we are logically bound not to assume the existence of these higher faculties until good reasons shall have been shown for such existence. In other words, we are bound to accept the principle above enunciated : that in no case is an animal activity to be interpreted as the outcome of the exercise of a higher Psychical faculty, if it can be fairly interpreted as the outcome of the exercise of one which stands lower in the psychological scale.
In this statement, and in the foregoing discussion, the use of the word "faculty" is perhaps unfortunate. If the reader finds the word too reminiscent of a "faculty psychology," with its-separate and distinct autonomous spheres of influence, Let him substitute this statement for the one given above :-In no case is an animal activity to be interpreted in terms of higher psychological processes, if it can be fairly interpreted in terms of processes which stand lower in the scale of psychological evolution and development. To this, however, it should be added, lest the range of the principle be misunderstood, that the canon by no means excludes the interpretation of a particular activity in terms of the higher processes, if we already have independent evidence of the occurrence of these higher processes in the animal under observation,