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CHAPTER IX


DEFINITIONS OF PSYCHOLOGY


Let us resume the study of the preceding ideas in another form. Since, moreover, to define mind is at the same time to define psychology, let us seek for the truth which we can glean from the definitions of this science. Our object is not to discover an exact definition, but to make use of those already existing.

To define psychology is to describe the features of the domain over which this science holds sway, and at the same time to indicate the boundaries which separate it from its neighbours. At first sight this is an affair of geometric survey, presenting no kind of difficulty; for psychology does not merge by insensible transitions into the neighbouring sciences, as physics does with chemistry, for example, or chemistry with biology.

To all the sciences of external nature psychology offers the violent opposition of the moral to the physical world. It cannot be put in line with the physical sciences. It occupies, on the contrary, a position apart. It is the starting point, the most abstract and simple of the moral sciences; and it bears the same relation to them that mechanics does to the physical.

All this is doubtless true; and yet a very great difficulty has been experienced in condensing into a clear definition the essence of psychology. This is proved by the multiplicity of definitions attempted. They are so many because none of them has proved completely satisfactory. Their abundance shows their insufficiency. I will try to introduce a little order into these attempts, and propose to distribute the definitions of psychology into the following categories:—

1. The definition by substance; the metaphysical definition par excellence.
2. The definition by enumeration.
3. The definition by method.
4. The definition by degree of certainty.
5. The definition by content.
6. The definition by point of view.
7. The definition by the peculiar nature of mental laws.

We will rapidly run through this series of efforts at definition, and shall criticise and reject nearly the whole of them; for the last alone seems exact—that is to say, in harmony with the ideas laid down above.

Metaphysical definition has to-day taken a slightly archaistic turn. Psychology used to be considered as the science of the soul. This is quite abandoned. Modern authors have adopted the expression and also the idea of Lange,[1] who was, I think, the first to declare that we ought to cultivate a soulless psychology. This categorical declaration caused an uproar, and a few ill-informed persons interpreted it to mean that the new psychology which has spread in France under cover of the name of Ribot, sought to deny the existence of the soul, and was calculated to incline towards materialism. This is an error.

It is very possible, indeed, that several adepts of the new or experimental psychology may be materialists from inward conviction. The exclusive cultivation of external facts, of phenomena termed material, evidently tends—this is a mystery to none—to incline the mind towards the metaphysical doctrine of materialism. But, after making this avowal, it is right to add at once that psychology, as a science of facts, is the vassal of no metaphysical doctrine. It is neither spiritualist, materialist, nor monist, but a science of facts solely. Ribot and his pupils have proclaimed this aloud at every opportunity. Consequently it must be recognised that the rather amphibological expression “soulless psychology” implies no negation of the existence of the soul. It is—and this is quite a different thing—rather an attitude of reserve in regard to this problem. We do not solve this problem; we put it on one side.

And, certainly, we are right to do so. The soul, viewed as a substance—that is, as a something distinct from psychical phenomena, which, while being their cause and support, yet remains inaccessible to our direct means of cognition—is only an hypothesis, and it cannot serve as objective to a science of facts. This would imply a contradiction in terms.

Unfortunately, we must confess that if it be right to relegate to metaphysics the discussion on the concept of the soul, it does not really suffice to purge our minds of all metaphysics; and a person who believes himself to be a simple and strict experimentalist is often a metaphysician without knowing it. These excommunications of metaphysics also seem rather childish at the present day. There is less risk than some years ago in declaring that: “Here metaphysics commence and positive science ends, and I will go no further.” There is even a tendency in modern psychologists to interest themselves in the highest philosophical problems, and to take up a certain position with regard to them.

The second kind of definition is, we have said, that by enumeration. It consists in placing before the eyes of the reader an assortment of psychological phenomena and then saying: “These are the things psychology studies.” One will take readily as samples the ideas, reasonings, emotions, and other manifestations of mental life. If this is only a strictly provisional definition, a simple introduction to the subject, we accept it literally. It may serve to give us a first impression of things, and to refresh the memories of those who, by a rather extraordinary chance, would not doubt that psychology studies our thoughts. But whatever may be the number of these deeply ignorant persons, they constitute, I think, a negligible quantity; and, after these preliminaries, we must come to a real definition and not juggle with the problem, which consists in indicating in what the spiritual is distinguished from the material. Let us leave on one side, therefore, the definitions by enumeration.

Now comes the definition by method. Numbers of authors have supposed that it is by its method that psychology is distinguished from the other sciences.

To the mind is attached the idea of the within, to nature the idea of being without the mind, of constituting a “without” (un dehors). It is a vague idea, but becomes precise in a good many metaphors, and has given rise to several forms of speech. Since the days of Locke, we have always spoken of the internal life of the mind as contrasted with the external life, of subjective reality as contrasted with objective reality; and in the same way we oppose the external senses to the inner sense (the internal perception), which it has at times been proposed to erect into a sixth sense. Though no longer quite the Cartesian dualism, this is still a dualism.

It has also been said that psychology is the science of introspection, and, in addition, that scientific psychology is a controlled introspection. This science of the “internal facts of man” would thus be distinguished from the other natural sciences which are formed by the use of our outer senses, by external observation—that is to say, to use a neologism, by externospection. This verbal symmetry may satisfy for a moment minds given to words, but on reflection it is perceived that the distinction between introspection and externospection does not correspond to a fundamental and constant difference in the nature of things or in the processes of cognition. I acknowledge it with some regret, and thus place myself in contradiction with myself; for I for a long time believed, and have even said in print, that psychology is the science of introspection. My error arose from my having made too many analyses of detail, and not having mounted to a sufficiently wide-reaching conception. The definition I have given of consciousness is the implied condemnation of the above ideas. Consciousness, being nothing but an act of revelation, has neither a within nor a without; it does not correspond to a special domain which would be an inner one with regard to another domain.

Every consideration on the position of things is borrowed from the sphere of the object, and remains foreign to the sphere of the consciousness. It is by an abuse of language that we speak of the outer world in relation to the world of consciousness, and it is pure imagination on the part of philosophers to have supposed that our sensations are first perceived as internal states and states of consciousness, and are subsequently projected without to form the outer world. The notion of internal and external is only understood for certain objects which we compare by position to certain others.

In fact, we find that the opposition between an external and an internal series is generally founded on two characteristics: sensation is considered external in relation to the idea, and an object of cognition is considered as internal when it is accessible only to ourselves. When these two characteristics are isolated from each other, one may have doubts; but when they co-exist, then the outwardness or inwardness appears fully evidenced. We see then that this distinction has nothing to do with the value of consciousness, and has nothing mental about it.

It is thus that our ideas are judged from internal events. It is our microcosm opposed to the macrocosm. It is the individual opposed to the social. Looking at an external object, we remain in communion with our fellows, for we receive, or think we receive, identical sensations. At all events, we receive corresponding sensations. On the other hand, my thought is mine, and is known to me alone; it is my sanctuary, my private closet, where others do not enter. Every one can see what I see, but no one knows what I think.

But this difference in the accessibility of phenomena is not due to their peculiar nature. It is connected with a different fact, with the modes of excitement which call them forth. If the visual sensation is common to all, it is because the exciting cause of the sensation is an object external to our nervous systems, and acting at a distance on all.[2] The tactile sensation is at the beginning more personal to the one who experiences it, since it requires contact; and the lower sensations are in this intimacy still in progress. And then, the same object can give rise, in common-place circumstances, to a sensation either common to all beings or special to one alone. The capsule of antipyrine which I swallow is, before my doing so, visible to all eyes; once in my mouth, I am the only one to perceive it. It is therefore possible that the same sensation, according to the displacements of the object which excites it, may make part of the internal or of the external series; and as all psychic life is sensation, even effort, and, as we are assured, emotion, it follows that our argument extends to all the psychical elements.

Finally, the internal or external character of events, which might be called their geographical position, is a characteristic which has no influence upon the method destined to take cognisance of it. The method remains one. Introspection does not represent a source of cognition distinct from externospection, for the same faculties of the mind—reason, attention, and reflection—act on sensation, the source of the so-called external sciences, and on the idea, the source of the so-called inner science. A fact can be studied by essentially the same process, whether regarded by the eyes or depicted by the memory. The consciousness changes its object and orientation, not its nature. It is as if, with the same opera-glass, we looked in turn at the wall of the room and through the window. I can even quote on this point a significant fact: there are observers who are organised in such a way that they especially observe by memory. Placed before the sensorial phenomenon which strikes their senses, they are sometimes amazed, as if hypnotised; they require to get away from it to regain consciousness of themselves, to analyse the fact, and to master it, and it is by means of the memory that they study it, on condition, of course, of afterwards coming back to verify their conclusions by a fresh observation from nature. Will it be said that the physicist, the chemist, or the biologist who follows this slow method, and who thus observes retroactively, practises physics and biology by introspection? Evidently this would be ridiculous.

Conversely, introspection may, in certain cases, adopt the procedure of externospection. No doubt it would be inexact to say that the perception of one of our ideas always takes place through the same mechanism as the perception of one of our sensations. To give an account of what we think does not imply the same work as in the case of what we see; for, generally, our thoughts and our images do not appear to us spontaneously. They are first sought for by us, and are only realised after having been wished for. We go from the vague to the precise, from the confused to the clear: the direction of thought precedes, then, its realisation in images; and the latter, being expected, is necessarily comprehended when it is formed. But we may come across curious circumstances in which it is the image which has precedence over its appearance, and in that case it is exact to say that this uninvoked image must be interpreted and recognised as if it were an external object. In cases of this kind, there passes through our mind something which surprises us. I see, by internal vision, a face with a red nose, and I have to search my memory for a long time, even for days, in order to give precision to the vague feeling that I have seen it before, so as to finally say with confidence, “It is So and So!” Or else I hear in my inner ear a certain voice, with a metallic tone and authoritative inflections: this voice pronounces scientific phrases, gives a series of lectures, but I know not to whom it belongs, and it costs me a long effort to reach the interpretation: it is the voice of M. Dastre! There is, then, a certain space of time, more or less long, in which we can correctly assert that we are not aware of what we are thinking; we are in the presence of a thought in the same state of uncertainty as in that of an external, unknown, and novel object. The labour of classification and of interpretation cast upon us is of the same order; and, when this labour is effected incorrectly, it may end in an illusion. Therefore illusions of thought are quite as possible as illusions of the senses, though rarer for the reasons above stated. But the question of frequency has no theoretical importance.

I have shown elsewhere, by experiments on hysterics, that it is possible by the intermediary of their insensibility to touch to suggest ideas on the value of which the patients make mistakes. For instance, you take the finger in which they have no sensation, you touch it, you bend it. The patient, not seeing what is done, does not feel it, but the tactile sensation unfelt by their principal consciousness somehow awakes the visual image of the finger; this enters into the field of consciousness, and most often is not recognised by the subject, who describes the occurrence in his own way; he claims, for instance, that he thinks of sticks or of columns. In reality he does not know of what he is thinking, and we know better than he. He is thinking of his finger, and does not recognise it.

All these examples show that the clearly defined characteristics into which it is sought to divide extrospection and introspection do not exist. There is, however, a reason for preserving the distinction, because it presents a real interest for the psychology of the individual. These two words introspection and extrospection admirably convey the difference in the manner of thinking between those who from preference look, and those who from preference reflect. On the one hand, the observers, who are often men of action; on the other, the speculators, who are often mystics. But it would be no more legitimate by this means to separate psychology and physics than to say, for instance, “There are two kinds of geology: one is the geology of France, for one is acquainted with it without going from home, and the other is that of the rest of the world, because in order to know it one must cross the frontier.”

We reject, therefore, the definition drawn from the difference of method. At bottom there is no difference of method, but only differences of process, of technique. The method is always the same, for it is derived from the application of a certain number of laws to the objects of cognition, and these laws remain the same in all spheres of application.

Here is another difference of method which, if it were true, would have an incalculable importance. Psychology, we are told, is a science of direct and immediate experiment; it studies facts as they present themselves to our consciousness, while the natural sciences are sciences of indirect and mediate experiment, for they are compelled to interpret the facts of consciousness and draw from them conclusions on nature. It has also been said, in a more ambitious formula, “The science of physical objects is relative; psychological science is absolute.”

Let us examine this by the rapid analysis of any perception taken at haphazard. What I perceive directly, immediately, we are told, is not the object, it is my state of consciousness; the object is inferred, concluded, and taken cognisance of through the intermediary of my state of consciousness. We only know it, says Lotze, circa rem. It is therefore apprehended less immediately, and every natural science employs a more roundabout method than that of psychology. This last, by studying states of consciousness, which alone are known to us directly, comprehends reality itself, absolute reality. “There is more absolute reality,” M. Rabier boldly says, “in the simple feeling that a man, or even an animal, has of its pain when beaten than in all the theories of physics, for, beyond these theories, it can be asked, what are the things that exist. But it is an absurdity to ask one’s self if, beyond the pain of which one is conscious, there be not another pain different from that one.”[3]

Let us excuse in psychologists this petty and common whim for exaggerating the merit of the science they pursue. But here the limit is really passed, and no scholar will admit that the perception and representation of a body, as it may take place in the brain of a Berthelot, can present any inferiority as a cognition of the absolute, to the pain felt by the snail I crush under my foot. Nobody except metaphysicians will acknowledge that psychology is a more precise and certain science than physics or chemistry.

The criterion furnished by the development of the respective sciences would prove just the contrary. The observations of psychology are always rather unprecise. Psychological phenomena, notwithstanding the efforts of Fechner and his school, are not yet measured with the same strictness and ease as the tangible reality. To speak plainly, the psychologist who vaunts the superiority of his method, and only shows inferior results, places himself in a somewhat ridiculous and contradictory position; he deserves to be compared to those spiritualists who claim the power of evoking the souls of the illustrious dead and only get from them platitudes.

In the main the arguments of the metaphysicians given above appear to me to contain a grave error. This consists in supposing that the natural sciences study the reality hidden beneath sensation, and only make use of this fact as of a sign which enables them to get back from effect to cause. This is quite inexact. That the natural sciences are limited by sensation is true; but they do not go outside it, they effect their constructions with sensation alone. And the reason is very simple: it is the only thing they know. To the metaphysical psychologist, who claims sensation as his own property, saying, “But this sensation is a state of my consciousness, it is mine, it is myself,” the physicist has the right to answer: “I beg your pardon! this sensation is the external object that I am studying; it is my column of mercury, my spring, my precipitate, my amoeba; I comprehend these objects directly, and I want no other.” Psychology finds itself, therefore, exactly on the same footing as the other sciences in the degree in which it studies sensations that it considers as its own property. I have already said that the sensations proper to psychology are hardly represented otherwise than by the emotional sensations produced by the storms in the apparatus of organic life.

We now come to the definitions by content. They have been numerous, but we shall only quote a few. The most usual consists in saying, that Psychology studies the facts of consciousness. This formula passes, in general, as satisfactory. The little objection raised against it is, that it excludes the unconscious facts which play so important a part in explaining the totality of mental life; but it only requires some usual phrase to repair this omission. One might add, for instance, to the above formula: conscious facts and those which, while unconscious under certain conditions, are yet conscious in others.

This is not, however, the main difficulty, which is far more serious. On close examination, it is seen that the term, fact of consciousness, is very elastic, and that for a reason easy to state. This is, that all facts which exist and are revealed to us reach us by the testimony of the consciousness, and are, consequently, facts of consciousness. If I look at a locomotive, and analyse its machinery, I act like a mechanic; if I study under the microscope the structure of infusoria, I practise biology; and yet the sight of the locomotive, the perception of the infusoria, are just facts of consciousness, and should belong to psychology, if one takes literally the above definition, which is so absolute that it absorbs the entire world into the science of the mind. It might, indeed, be remarked that certain phenomena would remain strictly psychological, such as, for instance, the emotions, the study of which would not be disputed by any physical science; for the world of nature offers us nothing comparable to an emotion or an effort of will, while, on the other hand, everything which is the object of physical science—that is, everything which can be perceived by our external senses—may be claimed by psychology. Therefore, it is very evident the above definition is much too wide, and does not agree with solo definito. It does not succeed in disengaging the essential characteristic of physics. This characteristic indeed exists, and we foresee it, but we do not formulate it.

Another definition by content has not been much more happy. To separate the material from the moral, the conception of Descartes was remembered, and we were told that: “Psychology is the science of what exists only in time, while physics is the science of what exists at once in time and in space.”

To this theoretical reasoning it might already be objected that, in fact, and in the life we lead, we never cease to localise in space, though somewhat vaguely, our thought, our Ego, and our intellectual whole. At this moment I am considering myself, and taking myself as an example. I am writing these lines in my study, and no metaphysical argument can cause me to abandon my firm conviction that my intellectual whole is in this room, on the second floor of my house at Meudon. I am here, and not elsewhere. My body is here; and my soul, if I have one, is here. I am where my body is; I believe even that I am within my body.

This localisation, which certainly has not the exactness nor even the characteristics of the localisation of a material body in space, seems to me to result from the very great importance we attach to the existence of our body in perception and in movement. Our body accompanies all our perceptions; its changes of position cause these perceptions to vary; the accidents which happen to it bring us pleasure or pain. Some of its movements are under our orders; we observe that others are the consequences of our thoughts and our emotions. It occupies, therefore, among the objects of cognition a privileged place, which renders it more intimate and more dear to us than other objects. There is no need to inquire here whether, in absolute reality, I am lodged within it, for this “I” is an artificial product manufactured from memories. I have before explained what is the value of the relation subject-object. It is indisputable that in the manufacture of the subject we bring in the body. This is too important an element for it not to have the right to form part of the synthesis; it is really its nucleus. As, on the other hand, all the other elements of the synthesis are psychical, invisible, and reduced to being faculties and powers, it may be convenient to consider them as occupying the centre of the body or of the brain. There is no need to discuss this synthesis, for it is one of pure convenience. As well inquire whether the personality of a public company is really localised at its registered offices, round the green baize cover which adorns the table in the boardroom.

Another definition of psychology, which is at once a definition by content and a definition by method, has often been employed by philosophers and physiologists. It consists in supposing that there really exist two ways of arriving at the cognition of objects: the within and the without. These two ways are as opposed to each other as the right and wrong side of a stuff. It is in this sense that psychology is the science of the within and looks at the wrong side of the stuff, while the natural sciences look at the right side. And it is so true, they add, that the same phenomenon appears under two radically different forms according as we look at it from the one or the other point of view. Thus, it is pointed out to us, every one of our thoughts is in correlation with a particular state of our cerebral matter; our thought is the subjective and mental face; the corresponding cerebral process is the objective and material face.

Then the difference between representation, which is a purely psychological phenomenon, and a cerebral state which is a material one, and reducible to movement, is insisted upon; and it is declared that these two orders of phenomena are separated by irreducible differences.

Lastly, to take account of the meaning of these differences, and to explain them, it is pointed out that they are probably connected with the modes of cognition which intervene to comprehend the mental and the physical. The mental phenomenon, we are told, is comprehended by itself, and as it is; it is known without any mystery, and in its absolute reality. The physical phenomenon, on the contrary, only reaches us through the intermediary of our nerves, more or less transformed in consequence by the handling in transport. It is an indirect cognition which causes us to comprehend matter; we have of this last only a relative and apparent notion, which sufficiently explains how it may differ from a phenomenon of thought.

I have already had occasion to speak of this dualism, when we were endeavouring to define sensation. We return to its criticism once more, for it is a conception which in these days has become classic; and it is only by repeatedly attacking it that it will be possible to demonstrate its error.

To take an example: I look at the plain before me, and see a flock of sheep pass over it. At the same time an observer is by my side and is not looking at the same thing as myself. It is not at the plain that he looks; it is, I will suppose, within my brain. Armed with a microscope à la Jules Verne, he succeeds in seeing what is passing beneath my skull, and he notices within my fibres and nerve cells those phenomena of undulation which physiologists have hitherto described hypothetically. This observer notices then, that, while I am looking over the plain, my optic nerve conveys a certain kind of movements—these are, I suppose, displacements of molecules which execute a complicated kind of dance. The movement follows the course of the optic nerve, traverses the chiasma, goes along the fascia, passes the internal capsule, and finally arrives at the visual centres of the occipital region. Here, then, are the two terms of comparison constituted: on the one hand, we have a certain representation—that is, my own; and on the other hand, coinciding with this representation, we have the dynamic changes in the nerve centres. These are the two things constituting the right and wrong side of the stuff. We shall be told: “See how little similarity there is here! A representation is a physical fact, a movement of molecules a material fact.” And further, “If these two facts are so little like each other, it is because they reach us by two different routes.”

I think both these affirmations equally disputable. Let us begin with the second. Where does one see that we possess two different sources of knowledge? Or that we can consider an object under two different aspects? Where are our duplicate organs of the senses, of which the one is turned inward and the other outward? In the example chosen for this discussion, I have supposed two persons, each of whom experiences a visual perception. One looks at one object, the other at another; but both are looking with the same organs of sense, that is, with their eyes. How is it possible to understand that these eyes can, in turn, according to the necessity of the moment, see the two faces, physical and mental, of the same object?

They are the two faces of an identical object, is the answer made to us, because the two visions, although applied to the same object, are essentially different. On the one hand is a sensation of displacement, of movement, of a dance executed by the molecules of some proteid substance; on the other hand is a flock of sheep passing over the plain at a distance of a hundred metres away.

It seems to me that here also the argument advanced is not sound. In the first place, it is essential to notice that not only are the two paths of cognition identical, but also that the perceptions are of the same nature. There is in this no opposition between the physical and the mental. What is compared are the two phenomena, which are both mixed and are physico-mental—physical, through the object to which they are applied, mental, through the act of cognition they imply. To perceive an object in the plain and to perceive a dynamic state of the brain are two operations which each imply an act of cognition; and, in addition, the object of this knowledge is as material in the one as in the other case. A flock of sheep is matter just as much as my brain.

No doubt, here are objects which differ; my observer and myself have not the same perception. I acknowledge, but do not wonder at it. How could our two perceptions be similar? I look at the sheep, and he at the interior of my brain. It is not astonishing that, looking at such different objects, we should receive images also different. Or, again, if this other way of putting it be preferred, I would say: the individual A looks at the flock through the intermediary of his nervous system, while B looks at it through that of two nervous systems, put as it were end to end (though not entirely), his own nervous system first, and then that of A. How, then, could they experience the same sensation?

They could only have an identical sensation if the idea of the ancients were to be upheld, who understood the external perception of bodies to result from particles detaching themselves from their bodies, and after a more or less lengthy flight, striking and entering into our organs of sense.[4]

Let us imagine, just for a moment, one of our nerves—the optic nerve, for instance—transformed into a hollow tube, along which the emissions of miniatures should wend their way. In this case, evidently, if so strange a disposition were to be realised, and if B could see what was flowing in the optic nerve of A, he would experience a sensation almost analogous to that of A. Whenever the latter saw a dog, a sheep, or a shepherd, B would likewise see in the optic canal minute dogs, microscopic sheep, and Lilliputian shepherds. At the cost of such a childish conception, a parity of content in the sensations of our two spectators A and B might be supposed. But I will not dwell on this.

The above considerations seem to me to explain the difference generally noticed between thought and the physiological process. It is not a difference of nature, an opposition of two essences, or of two worlds—it is simply a difference of object; just that which separates my visual perception of a tree and my visual perception of a dog. There remains to know in what manner we understand the relation of these two processes: this is another problem which we will examine later.

Since the content does not give us the differentiation we desire, we will abandon the definitions of psychology by content. What now remains? The definitions from the point of view. The same fact may be looked at, like a landscape, from different points of view, and appears different with the changes therein. It is so with the facts we consider psychical, and the autonomy of psychology would thus be a matter of point of view.

It has, then, been supposed—and this is a very important proposition—that the distinctive feature of psychical facts does not consist in their forming a class of particular events. On the contrary, their characteristic is to be studied in their dependency on the persons who bring them about. This interesting affirmation is not new: it may be read in the works of Mach, Külpe, Münsterberg, and, especially, of Ebbinghaus, from whom I quote the following lines of quite remarkable clearness: “Psychology is not distinguished from sciences like physics and biology, which are generally and rightly opposed to it, by a different content, in the way that, for instance, zoology is distinguished from mineralogy or astronomy. It has the same content, but considers it from a different point of view and with a different object. It is the science, not of a given part of the world, but of the whole world, considered, however, in a certain relation. It studies, in the world, those formations, processes, and relations, the properties of which are essentially determined by the properties and functions of an organism, of an organised individual. . . . Psychology, in short, considers the world from an individual and subjective point of view, while the science of physics studies it as if it were independent of us.”

Over these definitions by point of view, one might quibble a little; for those who thus define psychology are not always consistent with themselves. In other passages of their writings they do not fail to oppose psychical to physiological phenomena, and they proclaim the irreducible heterogeneity of these two orders of phenomena and the impossibility of seeing in physics the producing cause of the moral. Ebbinghaus is certainly one of the modern writers who have most strongly insisted on this idea of opposition between the physiological and the psychical, and he is a convinced dualist. Now I do not very clearly understand in what the principle of heterogeneity can consist to a mind which admits, on the other hand, that psychology does not differ from the physical sciences by its content.

However, I confine myself here to criticising the consequences and not the starting point. The definition of the psychical phenomenon by the point of view seems to me correct, although it has more concision than clearness; for it rests especially upon a material metaphor, and the expression “point of view” hardly applies except to the changes of perspective furnished by visible objects.

It would be more exact to say that psychology specially studies certain objects of cognition, such as those which have the character of representations (reminiscences, ideas, concepts), the emotions, the volitions, and the reciprocal influences of these objects among themselves. It studies, then, a part of the material world, of that world which till now has been called psychological, because it does not come under the senses, and because it is subjective and inaccessible to others than ourselves; it studies the laws of those objects, which laws have been termed mental.[5]

These laws are not recognised, popularly speaking, either in physics or in biology; they constitute for us a cognition apart from that of the natural world. Association by resemblance, for example, is a law of consciousness; it is a psychological law which has no application nor counterpart in the world of physics or biology. We may therefore sum up what has been said by the statement that psychology is the study of a certain number of laws, relations, and connections.

As to the particular feature which distinguishes mental from physical laws, we can formulate it, as does William James, by saying that the essence of a mental law is to be teleological, or, if the phrase be preferred, we can say that mental activity is a finalistic activity, which expends itself as will in the pursuit of future ends, and as intelligence in the choice of the means deemed capable of serving those ends. An act of intelligence is recognised by the fact of its aiming at an end, and employing for this end one means chosen out of many. Finality and intelligence are thus synonymous. In opposition to mental law, physical law is mechanical, by which expression is simply implied the absence of finality. Finality opposed to mechanism; such is the most concise and truest expression in which must be sought the distinctive attribute of psychology and of the moral sciences, the essential characteristic by which psychological are separated from physical facts.

I think it may be useful to dwell a little on the mental laws which I have just opposed to the physical, and whose object is to assure preadaptation and form a finality.[6] Their importance cannot be exaggerated. Thanks to his power of preadaptation, the being endowed with intelligence acquires an enormous advantage over everything which does not reason. No doubt, as has been shrewdly remarked, natural selection resembles a finality, for it ends in an adaptation of beings to their surroundings. There is therefore, strictly speaking, such a thing as finality without intelligence. But the adaptation resulting therefrom is a crude one, and proceeds by the elimination of all that does not succeed in adapting itself; it is a butchery. Real finalism saves many deaths, many sufferings, and many abortions.[7]

Let us examine, then, the process of preadaptation; it will enable us to thoroughly comprehend, not only the difference between the physical and the psychical laws, but the reason why the psychical manages in some fashion to mould itself upon the physical law.

Now, the means employed by preadaptation is, if we take the matter in its simplest form, to be aware of sensations before they are experienced. If we reflect that all prevision implies a previous knowledge of the probable trend of events, it will be understood that the part played by intelligence consists in becoming imbued with the laws of nature, for the purpose of imitating its workings. By the laws of nature, we understand here only that order of real sensations, the knowledge of which is sufficient to fulfil the wants of practical life. To us there are always gaps in this order, because the sensation it is important for us to know is separated from us either by the barriers of time or of space, or by the complication of useless sensations. Thence the necessity of interpolations. That which we do not perceive directly by our senses, we are obliged to represent to ourselves by our intelligence; the image does the work of sensation, and supplements the halting sensation in everything which concerns adaptation.

To replace the inaccessible sensation by the corresponding image, is therefore to create in ourselves a representation of the outer world which is, on all the points most useful to us, more complete than the direct and sensorial presentation of the moment. There is in us a power of creation, and this power exercises itself in the imitation of the work of nature; it imitates its order, it reconstitutes on the small scale adapted to our minds, the great external order of events. Now, this work of imitation is only really possible if the imitator has some means at his disposal analogous to those of the model.

Our minds could not divine the designs of nature, if the laws of images had nothing in common with the laws of nature. We are thus led to confront these two orders of laws with each other; but, before doing so, one more preliminary word is necessary. We have up till now somewhat limited the problem, in order to understand it. We have reduced the psychological being to one single function, the intellectual, and to one single object of research, the truth. This is, however, an error which has often been committed, which is now known and catalogued, called intellectualism, or the abuse of intellectualism. It is committed for this very simple reason, that it is the intellectual part of our being which best allows itself to be understood, and, so to speak, intellectualised. But this leaves out of the question a part of our entire mental being so important and so eminent, that if this part be suppressed, the intelligence would cease to work and would have no more utility than a machine without motive power. Our own motive power is the will, the feeling, or the tendency. Will is perhaps the most characteristic psychical function, since, as I have already had occasion to say, nothing analogous to it is met with in the world of nature. Let us therefore not separate the will from the intelligence, let us incarnate them one in the other; and, instead of representing the function of the mind as having for its aim knowledge, foresight, the combination of means, and self-adaptation, we shall be much nearer the truth in representing to ourselves a being who wills to know, wills to foresee, and wills to adapt himself, for, after all, he wills to live.

Having said this, let us compare the psychological law and that of nature. Are they identical? We shall be told that they are not, since, as a fact, errors are committed at every moment by the sudden failures of human reason. This is the first idea which arises. Human error, it would seem, is the best proof that the two laws in question are not alike, and we will readily add that a falling stone does not mistake its way, that the crystal in the course of formation does not miss taking the crystalline shape, because they form part of physical nature, and are subject in consequence to its determinism. But this is faulty reasoning, and a moment of reflection demonstrates it in the clearest possible manner; for adaptation may miss its aim without the being who adapts himself and his surroundings necessarily obeying different laws. When the heat of a too early spring causes buds to burst forth prematurely which are afterwards destroyed by frost, there is produced a fault of adjustment which resembles an error of adaptation, and the bringing forward of this error does not necessarily imply that the tree and the whole of physical nature are obeying different laws. Moreover, the difference between the laws of nature and those of the understanding does not need deduction by reasoning from an abstract principle; it is better to say that it is directly observable, and this is how I find that it presents itself to us.

The essential law of nature is relatively easy to formulate, as it is comprised in the very definition of law. It simply consists in the sentence: uniformity under similar conditions. We might also say: a constant relation between two or several phenomena, which can also be expressed in a more abstract way by declaring that the law of nature rests on the combination of two notions, identity and constancy.

On the other hand, the laws of our psychical activity partly correspond to the same tendencies, and it would be easy to demonstrate that the microcosm of our thoughts is governed by laws which are also an expression of these two combined notions of constancy and identity. It is, above all, in the working of the intellectual machine, the best known and the most clearly analysed up till now, that we see the application of this mental law which resembles, as we say, on certain sides, the physical law: and the best we can do for our demonstration will doubtless be to dissect our reasoning powers. Reason, a process essential to thought in action, is developed in accordance with a law which resembles in the most curious manner a physical law. It resembles it enough to imitate it, to conform to it, and, so to speak, to mould itself on it.

Now, the reason does not follow the caprices of thought, it is subject to rules; it results from the properties of the images, those properties which we have above referred to, the material character of which we have recognised, and which are two in number—similarity and contiguity, as they are termed in the jargon of the schools. They are properties which have for their aim to bring things together, to unite, and to synthetise. They are unceasingly at work, and so apparent in their labour that they have long been known. We know, since the time of Aristotle, that two facts perceived at the same time reproduce themselves together in the memory—this is the law of contiguity; and that two facts perceived separately, but which are similar, are brought together in our mind—this is the law of similarity.

Now, similarity and contiguity form by combination the essential part of all kinds of reasoning, and this reasoning, thus understood, works in a fashion which much resembles (we shall see exactly in what degree) a physical law. I wish to show this in a few words. What renders my demonstration difficult and perhaps obscure is, that we shall be obliged to bring together rather unexpectedly categories of phenomena which are generally considered separate.

The distinctive attribute of the reason consists, as I have said, in the setting to work of these two elementary properties, similarity and contiguity. It consists, in fact, in extending continuity by similarity; in endowing with identical properties and similar accompaniments things which resemble each other; in other words, it consists in impliedly asserting that the moment two things are identical in one point they are so for all the rest. This will be fairly well understood by imagining what takes place when mental images having the above-mentioned properties meet. Suppose that B is associated with C, and that A resembles B. In consequence of their resemblance the passing from A to B is easy; and then B suggesting C by contiguity, it happens that this C is connected with A connected, though, in reality, they have never been tried together. I say they are associated on the basis of their relation to B, which is the rallying point. It is thus that, on seeing a piece of red-hot iron (A), I conclude it is hot (C), because I recollect distinctly or unconsciously another piece of red-hot iron (B), of which I once experienced the heat. It is this recollection B which logicians, in their analysis of logical, verbal, and formal argument, call the middle term. Our representation of the process of reasoning is not special to argument. It also expresses the process of invention, and every kind of progress from the known to the unknown. It is an activity which creates relations, which assembles and binds together, and the connections made between different representations are due to their partial identities, which act as solder to two pieces of metal.

It will now be understood that these relations between the images curiously resemble the external order of things, the order of our sensations, the order of nature, the physical law. This is because this physical law also has the same character and expresses itself similarly. We might say “all things which resemble each other have the same properties,” or “all things alike on one point resemble each other on all other points.” But immediately we do so, the difference between the physical and the mental law becomes apparent. The formula we have given is only true on condition that many restrictions and distinctions are made.

The process of nature is so to do that the same phenomenon always unfolds itself in the same order. But this process is not always comprehended in real life, for it is hidden from our eyes by the manifold combinations of chance; in the reality that we perceive there is a crowd of phenomena which resemble each other but are not really the same. There are a number of phenomena which co-exist or follow each other without this order of co-existence or succession being necessary or constant. In other words, there are resemblances which are the marks of something, as a logician would say, and others which are not the marks of anything; there are relations of time and space which are the expression of a law; there are some which are accidental, and may possibly never be reproduced.

It would be a wonderful advantage if every scientific specialist would make out a list of the non-significant properties that he recognises in matter. The chemist, for example, would show us that specific weight has hardly any value in diagnosis, that the crystalline form of a salt is often not its own, that its colour especially is almost negligible because an immense number of crystals are white or colourless, that precipitation by a given substance does not ordinarily suffice to characterise a body, and so on. The botanist, on his part, would show us that, in determining plants, absolute dimension is less important than proportion, colour less important than form, certain structures of organs less important than others. The pathologist would teach us that most pathological symptoms have but a trivial value; the cries, the enervation, the agitation of a patient, even the delirium which so affects the bystanders, are less characteristic of fever than the rate of his pulse, and the latter less than the temperature of the armpit or the dryness of the tongue, &c. At every moment the study of science reveals resemblances of facts and contiguities of facts which must be neglected for the sake of others. And if we pass from this profound knowledge of the objects to the empirical knowledge, to the external perception of bodies, it is in immense number that one espies around one traps laid by nature. The sound we hear resembles several others, all produced by different causes; many of our visual sensations likewise lend themselves to the most varied interpretations; by the side of the efficient cause of an event we find a thousand entangled contingencies which appear so important that to disentangle them we are as much perplexed as the savage, who, unable to discriminate between causes and coincidences, returns to drink at the well which has cured him, carefully keeping to the same hour, the same gestures, and the same finery.

The reason of this is that the faculty of similarity and the faculty of contiguity do not give the distinction, necessary as it is, between resemblances and co-existences which are significant and those which are not. The causal nexus between two phenomena is not perceived as something apart and sui generis; it is not even perceived at all. We perceive only their relation in time and space, and it is our mind which raises a succession to the height of a causal connection, by intercalating between cause and effect something of what we ourselves feel when we voluntarily order the execution of a movement. This is not the place to inquire what are the experimental conditions in which we subject phenomena to this anthropomorphic transformation; it will suffice for us to repeat here that, in perception, a chance relation between phenomena impresses us in the same way as when it is the expression of a law.

Our intellectual machine sometimes works in accord with the external law and at others makes mistakes and goes the wrong way. Then we are obliged to correct it, and to try a better adjustment, either by profounder experimenting with nature (methods of concordance, discordance, variations, &c.), or by a comparison of different judgments and arguments made into a synthesis; and this collaboration of several concordant activities ends in a conclusion which can never represent the truth, but only the probable truth. The study of the laws of the mind shows us too clearly, in fact, their fluidity with regard to the laws of nature for us not to accept probabilism. There exists no certitude—only very varied degrees of probability. Daily practice contents itself with a very low degree of probability; judicial logic demands a rather higher one, especially when it is a question of depriving one of our fellow-creatures of liberty or life. Science claims one higher still. But there is never anything but differences of degrees in probability and conjecture.

This, then, is the definition of psychology that we propose. It studies a certain number of laws which we term mental, in opposition to those of external nature, from which they differ, but which, properly speaking, do not deserve the qualification of mental, since they are—or at least the best known of them are—laws of the images, and the images are material elements. Although it may seem absolutely paradoxical, psychology is a science of matter—the science of a part of matter which has the property of preadaptation.


  1. Lange, Histoire du Matérialisme, II., 2me. partie, chap. iii.
  2. Let us remark, in passing, how badly nature has organised the system of communication between thinking beings. In what we experience we have nothing in common with our fellows; each one experiences his own sensations and not those of others. The only meeting point of different minds is found in the inaccessible domain of the noumena.
  3. Elie Rabier, Leçons de Philosophie, “Psychologie,” p. 33.
  4. This seems to have been the opinion of Democritus. The modern doctrine of radiation from the human body, if established, would go nearly as far as the supposition in the text. Up till now, however, it lacks confirmation.—Ed.
  5. I am compelled, much against my will, to use throughout this passage an equivocal expression, that of “mental law,” or law of consciousness, or psychological law. I indicate by this the laws of contiguity and of similarity; as they result from the properties of the images, and as these are of a material nature, they are really physical and material laws like those of external nature. But how can all these laws be called physical laws without running the risk of confusing them one with the other?
  6. Finality seems to be here used in the sense of the doctrine which regards perfection as the final cause of existence.—Ed.
  7. See a very interesting article by E. Goblot, “La Finalité sans Intelligence,” Revue de Métaphysique, July 1900.