Franz Brentano (1874)
Source: Psychology from an Empirical Standpoint, (1874) Routledge & Kegan Paul, First two chapters, "Concept and Purpose of Psychology" and "Psychological Method with Special Reference to its Experiential Basis".
There are certain phenomena which once seemed familiar and obvious and appeared to provide an explanation for things which had been obscure. Subsequently, however, these phenomena began to seem quite mysterious themselves and began to arouse astonishment and curiosity. These phenomena, above all others, were zealously investigated by the great thinkers of antiquity. Yet little agreement or clarity has been reached concerning them to this day. It is these phenomena which I have made my object of study. In this work I shall attempt to sketch in general terms an accurate picture of their characteristics and laws. There is no branch of science that has borne less fruit for our knowledge of nature and life, and yet there is none which holds greater promise of satisfying our most essential needs. There is no area of knowledge, with the single exception of metaphysics, which the great mass of people look upon with greater contempt. And yet there is none to which certain individuals attribute greater value and which they hold in higher esteem. Indeed, the entire realm of truth would appear poor and contemptible to many people if it were not so defined as to include this province of knowledge. For they believe that the other sciences are only to be esteemed insofar as they lead the way to this one. The other sciences are, in fact, only the foundation; psychology is, as it were, the crowning pinnacle. All the other sciences are a preparation for psychology; it is dependent on all of them. But it is said to exert a most powerful reciprocal influence upon them. It is supposed to renew man's entire life and hasten and assure progress. And if, on the one hand, it appears to be the pinnacle of the towering structure of science, on the other hand, it is destined to become the basis of society and of its noblest possessions, and, by this very fast, to become the basis of all scientific endeavour as well.
1. The word "psychology" means science of the soul. In fact, Aristotle, who was the first to make a classification of science and to expound its separate branches in separate essays, entitled one of his works peri psychis. He meant by "soul" the nature, or, as he preferred to express it, the form, the first activity, the first actuality of a living being. And he considers something a living being if it nourishes itself, grows and reproduces and is endowed with the faculties of sensation and thought, or if it possesses at least one of these faculties. Even though he is far from ascribing consciousness to plants, he nevertheless considered the vegetative realm as living and endowed with souls. And thus, after establishing the concept of the soul, the oldest work on psychology goes on to discuss the most general characteristics of beings endowed with vegetative as well as sensory or intellectual faculties.
This was the range of problems which psychology originally encompassed. Later on, however, its field was narrowed substantially. Psychologists no longer discussed vegetative activities. On the assumption that it lacked consciousness, the entire realm of vegetative life ceased to be considered within the scope of their investigations. In the same way, the animal kingdom, insofar as it, like plants and inorganic things is an object of external perception, was excluded from their field of research. This exclusion was also extended to phenomena closely associated with sensory life, such as the nervous system and muscles, so that their investigation became the province of the physiologist rather than the psychologist.
This narrowing of the domain of psychology was not an arbitrary one. On the contrary, it appears to be an obvious correction necessitated by the nature of the subject matter itself. In fact, only when the unification of related fields and the separation of unrelated fields is achieved can the boundaries between the sciences be correctly drawn and their classification contribute to the progress of knowledge. And the phenomena of consciousness are related to one another to an extraordinary degree. The same mode of perception gives us all our knowledge of them, and numerous analogies relate higher and lower phenomena to one another. The things which external perception has shown us about living beings are seen as if from a different angle or even in a completely different form, and the general truths which we find here are sometimes the same principles which we see governing inorganic nature, and sometimes analogous ones.
It could be said, and not without some justification, that Aristotle himself suggests this later and more correct delimitation of the boundaries of psychology. Those who are acquainted with him know how frequently, while expounding a less advanced doctrine, he sets forth the rudiments of a different and more correct viewpoint. His metaphysics as well as his logic and ethics provides examples of this. In the third book of his treatise On the Soul, where he deals with voluntary actions, he dismisses the thought of investigating the organs that serve as intermediaries between a desire and the part of the body toward whose movement the desire is directed. For, he says, sounding exactly like a modern psychologist, such an investigation is not the province of one who studies the soul, but of one who studies the body. I say this only in passing so as perhaps to make it easier to convince some of the enthusiastic followers of Aristotle who still exist even in our own times.
We have seen how the field of psychology became circumscribed. At the same time, and in quite an analogous manner, the concept of life was also narrowed, or, if not this concept - for scientists still ordinarily use this term in its broad original sense - at least the concept of the soul.
In modern terminology the word "soul" refers to the substantial bearer of presentations and other activities which are based upon presentations and which, like presentations, are only perceivable through inner perception. Thus we usually call soul the substance which has sensations such as fantasy images, acts of memory, acts of hope or fear, desire or aversion.
We, too, use the word "soul" in this sense. In spite of the modification in the concept, then, there seems to be nothing to prevent us from defining psychology in the terms in which Aristotle once defined it, namely as the science of the soul. So it appears that just as the natural sciences study the properties and laws of physical bodies, which are the objects of our external perception, psychology is the science which studies the properties and laws of the soul, which we discover within ourselves directly by means of inner perception, and which we infer, by analogy, to exist in others.
Thus delimited, psychology and the natural sciences appear to divide the entire field of the empirical sciences between them, and to be distinguished from one another by a clearly defined boundary.
But this first claim, at least, is not true. There are facts which can be demonstrated in the same way in the domain of inner perception or external perception. And precisely because they are wider in scope, these more comprehensive principles belong exclusively neither to the natural sciences nor to psychology. The fact that they can be ascribed just as well to the one science as to the other shows that it is better to ascribe them to neither. They are, however, numerous and important enough for there to be a special field of study devoted to them. It is this field of study which, under the name metaphysics, we must distinguish from both the natural sciences and psychology.
Moreover, even the distinction between the two less general of these three great branches of knowledge is not an absolute one. As always happens when two sciences touch upon one another, here too borderline cases between the natural and mental sciences are inevitable. For the facts which the physiologist investigates and those which the psychologist investigates are most intimately correlated, despite their great differences in character. We find physical and mental properties united in one and the same group. Not only may physical states be aroused by physical states and mental states by mental, but it is also the case that physical states have mental consequences and mental states have physical consequences.
Some thinkers have distinguished a separate science which is supposed to deal with these questions. One in particular is Fechner, who named this branch of science "psychophysics" and called the famous law which he established in this connection the "Psychophysical Law." Others have named it, less appropriately, "physiological psychology."
Such a science is supposed to eliminate all boundary disputes between psychology and physiology. But would not new and even more numerous disputes arise in their place between psychology and psychophysics on the one hand and between psychophysics and physiology on the other? Ort is it not obviously the task of the psychologist to ascertain the basic elements of mental phenomena? Yet the psychophysicist must study them too, because sensations are aroused by physical stimuli. Is it not the task of the physiologist to trace voluntary as well as reflex actions back to the origins through an uninterrupted causal chain? Yet the psychophysicist, too, will have to investigate the first physical effects of mental causes.
Let us not, then, be unduly disturbed by the inevitable encroachment of physiology upon psychology and vice versa. These encroachments will be no greater than those which we observe, for example, between physics and chemistry. They do nothing to refute the correctness of the boundary line we have established; they only show that, justified as it is, this distinction, like every other distinction between sciences, is somewhat artificial. Nor will it be in any way necessary to treat the whole range of so-called psychophysical questions twice, i.e. once in physiology and once in psychology. In the case of each of these problems we can easily show which field contains the essential difficulty. Once this difficulty is solved, the problem itself is as good as solved. For example, it will definitely be the task of the psychologist to ascertain the first mental phenomena which are aroused by a physical stimulus, even if he cannot dispense with looking at physiological facts in so doing. By the same token, in the case of voluntary movements of the body, the psychologist will have to establish the ultimate and immediate mental antecedents of the whole series of physical changes which are connected with them, but it will be the task of the physiologist to investigate the ultimate and immediate physical causes of sensation, even though in so doing he must obviously also look at the mental phenomenon. Likewise, with reference to movements that have mental causes, the physiologist must establish within his own field their ultimate and proximate effects.
Concerning the demonstration that there is a proportional relationship between increases in physical and mental causes and effects, i.e. the investigation of the so-called "Psychophysical Law," it seems to me that the problem has two parts, one of which pertains to the physiologist, while the other is the task of the psychologist. The first is to determine which relative differences in the intensity of physical stimuli correspond to the smallest noticeable differences in the intensity of mental phenomena. The second consists in trying to discover the relations which these smallest noticeable differences bear to one another. But is not the answer to the latter question immediately and completely evident? Is it not clear that all the smallest noticeable differences must be considered equal to one another ? This is the view which has been generally accepted. Wundt himself, in his Physiological Psychology (p. 295), offers the following argument: "A difference in intensity which is just barely noticeable is . . . a psychic value of constant magnitude. In fact, if one just noticeable difference were greater or smaller than another, then it would be greater or smaller than the just noticeable, which is a contradiction." Wundt does not realize that this is a circular argument. If someone doubts that all differences which are just noticeable are equal, then as far as he is concerned, being "just noticeable" is no longer a characteristic property of a constant magnitude. The only thing that is correct and evident a priori is that all just noticeable differences are equally noticeable, but not that they are equal. If that were so, every increase which is equal would have to be equally noticeable and every increase which is equally noticeable would have to be equal. But this remains to be investigated, and the investigation of this question, which is the job of the psychologist because it deals with laws of comparative judgement, could yield a result quite different from what was expected. The moon does seem to change position more noticeably when it is nearer the horizon than when it is high in the sky, when in fact it changes the same amount in the same amount of time in either case. On the other hand, the first task mentioned above undoubtedly belongs to the physiologist. Physical observations have more extensive application here. And it is certainly no coincidence that we have to thank a physiologist of the first rank such as E. H. Weber for paving the way for this law, and a philosophically trained physicist such as Fechner for establishing it in a more extended sphere.
So the definition of psychology which was given above appears to be justified, and its position among its neighbouring sciences to have been clarified.
2. Nevertheless, not all psychologists would agree to defining psychology as the science of the soul, in the sense indicated above. Some define it, rather, as the science of mental phenomena, thereby placing it on the same level as its sister sciences. Similarly, in their opinion, natural science is to be defined as the science of physical phenomena, rather than as the science of bodies.
Let us clarify the basis of this objection. What is meant by "science of mental phenomena" or "science of physical phenomena"? The words "phenomenon" or "appearance" are often used in opposition to "things which really and truly exist." We say, for example, that the objects of our senses, as revealed in sensation, are merely phenomena; colour and sound, warmth and taste do not really and truly exist outside of our sensations, even though they may point to objects which do so exist. John Locke once conducted an experiment in which, after having warmed one of his hands and cooled the other, he immersed both of them simultaneously in the same basin of water. He experienced warmth in one hand and cold in the other, and thus proved that neither warmth nor cold really existed in the water. Likewise, we know that pressure on the eye can arouse the same visual phenomena as would be caused by rays emanating from a so-called colored object. And with regard to determinations of spatial location, those who take appearances for true reality can easily be convinced of their error in a similar way. From the same distance away, things which are in different locations can appear to be in the same location, and from different distances away, things which are in the same location can appear to be in different locations. A related point is that movement may appear as rest and rest as movement. These facts prove beyond doubt that the objects of sensory experience are deceptive. But even if this could not be established so clearly, we would still have to doubt their veracity because there would be no guarantee for them as long as the assumption that there is a world that exists in reality which causes our sensations and to which their content bears certain analogies, would be sufficient to account for the phenomena.
We have no right, therefore, to believe that the objects of so-called external perception really exist as they appear to us. Indeed, they demonstrably do not exist outside of us. In contrast to that which really and truly exists, they are mere phenomena.
What has been said about the objects of external perception does not, however, apply in the same way to objects of inner perception. In their case, no one has ever shown that someone who considers these phenomena to be true would thereby become involved in contradictions. On the contrary, of their existence we have that clear knowledge and complete certainty which is provided by immediate insight. Consequently, no one can really doubt that a mental state which he perceives in himself exists, and that it exists just as he perceives it. Anyone who could push his doubt this far would reach a state of absolute doubt, a scepticism which would certainly destroy itself, because it would have destroyed any firm basis upon which it could endeavour to attack knowledge.
Defining psychology as the science of mental phenomena in order to make natural science and mental science resemble each other in this respect, then, has no reasonable justification.
There is another, quite different reason which generally motivates those who advocate such a definition, however. These people do not deny that thinking and willing really exist. And they use the expression "mental phenomena" or "mental appearances" as completely synonymous with "mental states", "mental processes," and "mental events," as inner perception reveals them to us. Nevertheless, their objection to the old definition, too, is related to the fact that on such a definition the limits of knowledge are misunderstood. If someone says that natural science is the science of bodies, and he means by "body" a substance which acts on our sense organs and produces presentations of physical phenomena, he assumes that substances are the cause of external appearances. Likewise, if someone says that psychology is the science of the soul, and means by "soul" the substantial bearer of mental states, then he is expressing his conviction that mental events are to be considered properties of a substance. But what entitles us to assume that there are such substances ? It has been said that such substances are not objects of experience; neither sense perception nor inner experience reveal substances to us. Just as in sense perception we encounter phenomena such as warmth, colour and sound, in inner perception we encounter manifestations of thinking, feeling and willing. But we never encounter that something of which these things are properties. It is a fiction to which no reality of any sort corresponds, or whose existence could not possibly be proved, even if it did exist. Obviously, then, it is not an object of science. Hence natural science may not be defined as the science of bodies nor may psychology be defined as the science of the soul. Rather, the former should be thought of simply as the science of physical phenomena, and the latter, analogously, as the science of mental phenomena. There is no such thing as the soul, at least not as far as we are concerned, but psychology can and should exist nonetheless, although, to use Albert Lange's paradoxical expression, it will be a psychology without a soul.
We see that the idea is not as absurd as the expression makes it seem. Even viewed in this way psychology still retains a wide area for investigation.
A glance at natural science makes this clear. For all the facts and laws which this branch of inquiry investigates when it is conceived of as the science of bodies will continue to be investigated by it when it is viewed only as the science of physical phenomena. This is how it is actually viewed at present by many famous natural scientists who have formed opinions about philosophical questions, thanks to the noteworthy trend which is now bringing philosophy and the natural sciences closer together. In so doing, they in no way restrict the domain of the natural sciences. All of the laws of coexistence and succession which these sciences encompass according to others, fall within their domain according to these thinkers, too.
The same thing is true of psychology. The phenomena revealed by inner perception are also subject to laws. Anyone who has engaged m scientific psychological research recognises this and even the layman can easily and quickly find confirmation for it in his own inner experience. The laws of the coexistence and succession of mental phenomena remain the object of investigation even for those who deny to psychology any knowledge of the soul. And with them comes a vast range of important problems for the psychologist, most of which still await solution.
In order to make more intelligible the nature of psychology as he conceived it, John Stuart Mill, one of the most decisive and influential advocates of this point of view, has given in his System of Logic synopsis of the problems with which psychology must be concerned.
In general, according to Mill, psychology investigates the laws which govern the succession of our mental states, i.e. the laws according to which one of these states produces another.
In his opinion, some of these laws are general, others more special. A general law, for example, would be the law according to which, "whenever any state of consciousness has once been excited in us, no matter by what cause . . . a state of consciousness resembling the former but inferior in intensity, is capable of being reproduced in us, without the presence of any such cause as excited it at first." Every impression, he says, using the language of Hume, has its idea. Similarly, there would also be certain general laws which determine the actual appearance of such an idea. He mentions three such Laws of Association of Ideas. The first is the Law of Similarity: "Similar ideas tend to excite one another." The second is the Law of Contiguity: "When two impressions have been frequently experienced . . . either simultaneously or in immediate succession, then when one of these impressions, or the idea of it recurs, it tends to excite the idea of the other." The third is the Law of Intensity: "Greater intensity in either or both of the impressions, is equivalent, in rendering them excitable by one another, to a greater frequency of conjunction."
The further task of psychology, according to Mill, is to derive from these general and elementary laws of mental phenomena more specific and more complex laws of thought. He says that since several mental phenomena often work concurrently, the question arises whether or not every such case is a case of a combination of causes in other words, whether or not effects and initial conditions are always related in the same way, as they are in the field of mechanics, where a motion is always the result of motion, homogeneous with its causes and in a certain sense the sum of its causes; or whether the mental realm also exhibits cases similar to the process of chemical combination, where you see in water none of the characteristics of hydrogen and oxygen, and in cinnabar none of the characteristics of mercury and sulphur. Mill himself believed it to be an established fact that both types of case exist in the domain of inner phenomena. Sometimes the processes are analogous to those in mechanics and sometimes to those in chemical reactions. For it may happen that several ideas coalesce in such a way that they no longer appear as several but seem to be a single idea of a completely different sort. Thus, for example, the idea of extension and three dimensional space develops from kinaesthetic sensations.
A series of new investigations is linked with this point. In particular the question will be raised as to whether belief and desire are cases of mental chemistry, i.e. whether they are the product of a fusion of ideas. Mill thinks that perhaps we must answer this question negatively. In whatever way it should be decided, perhaps even affirmatively, it would nevertheless be certain that entirely different fields of investigation are opened here. And so there emerges the new task of ascertaining, by means of special observations, the laws of succession of these phenomena, i.e. of ascertaining whether or not they are the products of such psychological chemistry, so to speak. In respect to belief, we would inquire what we believe directly; according to what laws one belief produces another; and what are the laws in virtue of which one thing is taken, rightly or erroneously, as evidence for another thing. In regard to desire, the primary task would consist in determining what objects we desire naturally and originally, and then we must go on to determine by what causes we are made to desire things originally indifferent or even disagreeable to us.
In addition, there is yet another rich area for investigation, one in which psychological and physiological research become more closely involved with one another than elsewhere. The psychologist, according to Mill, has the task of investigating how far the production of one mental state by others is influenced by confirmable physical states. Individual differences in susceptibility to the same psychological causes can be conceived as having a threefold basis. They could be an original and ultimate fact, they could be consequences of the previous mental history of those individuals, and they could be the result of differences in physical organisation. The attentive and critical observer will recognise, Mill thinks, that by far the greatest portion of a person's character can be adequately explained in terms of his education and outward circumstances. The remainder can, by and large, only be explained indirectly in terms of organic differences. And obviously this holds true not merely for the commonly recognised tendency of the deaf toward mistrustfulness, of the congenitally blind toward lustfulness, of the physically handicapped toward irritability, but also for many other, less easily intelligible phenomena. If there are still, as Mill grants, other phenomena, instincts in particular, which cannot be explained in any other way except directly in terms of one's particular physical organisation, we see that a wide field of investigation is assured for psychology in the area of ethology, i.e. formulating the laws of the formation of character.
This is a survey of psychological problems from the point of view of one of the most important advocates of psychology as a purely phenomenalistic science. It is really true that in none of the above-mentioned respects is psychology harmed by this new conception of it or by the point of view which leads to such a conception. As a matter of fact, in addition to the questions raised by Mill and those implicit in them, there are still others which are equally significant. Thus there is no shortage of important tasks for psychologists of this school, among whom are, at the present time, men who have made themselves pre-eminently of service to the advancement of science.
Nevertheless, the above conception of psychology seems to exclude at least one question which is of such importance that its absence alone threatens to leave a serious gap in this science. The very investigation which the older conception of psychology considered its main task, the very problem which gave the first impetus to psychological research can, apparently, no longer be raised on this view of psychology. I mean the question of continued existence after death. Anyone familiar with Plato knows that above all else it was the desire to ascertain the truth about this problem which led him to the field of psychology. His Phaedo is devoted to it, and other dialogues such as the Phaednus, Timaeas and the Republic come back to the question time and again. And the same thing is true of Aristotle. Admittedly he sets forth his proofs for the immortality of the soul in less detail than Plato, but it would be a mistake to conclude from this that the problem was any less important to him. In his logical works, where the doctrine of apodictic or scientific demonstration was necessarily the most important issue, he still discusses the problem, condensed into a few pages in the Posterior Analytics, in striking contrast to other long, extended discussions. In the Metaphysics he speaks of the deity only in a few short sentences in the last book, yet this study was avowedly so essential to him that he actually applied the name "theology" to the entire science, as well as the names "wisdom" and "first philosophy." In the same way, in his treatise On the Soul, he discusses man's soul and its immortality only very briefly, even when he is doing more than merely mentioning it in passing. Yet the classification of psychological problems at the beginning of this work clearly indicates that this question seemed to him to be the most important object of psychology. We are told there that the psychologist has the task, first of all, of investigating what the soul is, and then of investigating its properties, some of which appear to inhere in it alone and not in the body, and, as such, are spiritual. Furthermore he must investigate whether the soul is composed of parts or whether it is simple, and whether all the parts are bodily states or whether there are some which are not, in which case its immortality would be assured. The various aporiai which are linked with these questions show that we have hit upon the point which aroused this great thinker's thirst for knowledge most of all. This is the task to which psychology first devoted itself, and which gave it its first impetus for development. And it is precisely this task which appears, at the present time, to have fallen into disrepute and to have become impossible, at least from the standpoint of those who reject psychology as the science of the soul. For if there is no soul, then, of course, the immortality of the soul is out of the question.
This conclusion appears to be so immediately obvious that we cannot be surprised if some partisans of the conception here developed, A. Lange, for one, consider it to be self-evident. And so psychology offers us a drama similar to the one which occurred in the natural sciences. The alchemists' striving to produce gold from mixtures of elements first instigated chemical research, but the mature science of chemistry abandoned such ambitions as impossible. And somewhat in the manner of the well-known parable about the promise of the dying father, here too the heirs of earlier investigators have fulfilled the predictions of their predecessors. In the parable the sons industriously dug up the vineyard in which they believed a treasure was hidden, and if they did not find the buried gold, they reaped the fruit of the well-tilled soil instead. Something similar has happened to chemists, and would be happening to psychologists too. The mature science would have to abandon the question of immortality, but we could say that, as consolation, the zealous efforts which stemmed from a desire for the impossible have led to the solution of other questions whose far-reaching significance cannot be called into question.
Nevertheless, these two cases are not wholly identical. In place of the alchemists' dreams, reality offered a higher substitute. But in comparison with Plato's and Aristotle's hopes of reaching certainty concerning the continued existence of our better part after the dissolution of the body, the laws of association of ideas, of the development of convictions and opinions, and of the origin and growth of desire and love, would hardly be real compensation. The loss of this hope would appear to be far more regrettable. Consequently, if the opposition between these two conceptions of psychology really implied the acceptance or rejection of the question of immortality, this issue would become of paramount importance and would compel us to undertake metaphysical research concerning the existence of substance as the bearer of mental states.
Yet, whatever appearance of necessity there is for restricting the range of inquiry in this connection, it may still be no more than an appearance. In his time David Hume strongly opposed the metaphysicians who claimed to have found within themselves a substance which was the bearer of mental states. "For my part," he says, "when I enter most intimately into what I call myself, I always stumble on some particular perception or other, of heat or cold, light or shade, love or hatred, pain or pleasure. I never can catch myself at any time without a perception, and never can observe anything but the perception, When my perceptions are removed for any time, as by sound sleep; so long am I insensible of myself, and may truly be said not to exist." If certain philosophers claim that they perceive themselves as something simple and permanent, Hume does not want to contradict them, but of himself and of everyone else (this sort of metaphysician alone excepted), he is convinced "that they are nothing but a bundle or collection of different perceptions, which succeed each other with an inconceivable rapidity, and are in a perpetual flux and movement." We see, therefore, that Hume ranks unequivocally among the opponents of a substantial soul. Nevertheless, Hume himself remarks that in a conception such as his, all the proofs of immortality retain absolutely the same strength as in the traditional conception to which it is opposed. Of course, Albert Lange interprets this declaration as a mockery, and he may very likely be right, for it is known that Hume did not elsewhere scorn the use of malicious irony as a weapon. What Hume says, however, is not so obviously ridiculous as Lange and perhaps Hume himself might think. For even though it is self-evident that those who deny the existence of a substantial soul cannot speak of the immortality of the soul in the proper sense of the word, it still does not follow that the question of the immortality of the soul loses all meaning because we deny the existence of a substantial bearer of mental phenomena. This becomes evident as soon as you recognise that with or without a substantial soul you cannot deny that there is a certain continuity of our mental life here on earth. If someone rejects the existence of a substance, he must assume that such a continuity does not require a substantial bearer. And the question whether our mental life somehow continues even after the destruction of the body will be no more meaningless for him than for anyone else. It is wholly inconsistent for thinkers of this persuasion to reject, for the reasons mentioned, the question of immortality even in this, its essential sense, though it certainly would be more appropriate to call it immortality of life than immortality of the soul.
This was fully recognised by John Stuart Mill. In the passage from his Logic cited earlier, it is true that we do not find the question of immortality listed among those problems to be dealt with by psychology. In his work on Hamilton, however, he has developed with utmost clarity the very idea that we have just formulated.
Likewise, at the present time in Germany no important thinker has expressed his rejection of a substantial substrate for both mental and physical states as often and as categorically as Theodor Fechner. In his Psychophysics, in his Atomenlehre and in other writings, he criticises this doctrine, sometimes in earnest, sometimes humorously. Nevertheless, he candidly acknowledges his belief in immortality. It is clear, therefore, that even if one accepts the metaphysical view which led modern thinkers to substitute the definition of psychology as the science of mental phenomena for the traditional definition as the science of the soul, the field of psychology would not thereby be narrowed in any way, and, above all, it would not suffer any essential loss.
It would appear to be just as inadmissible, however, to accept this view without a thorough metaphysical investigation, as it is to reject it without a test. Just as there are eminent men who have questioned and denied that phenomena have a substantial bearer there also have been and still are other very famous scientists who firmly believe that they do. H. Lotze agrees with Aristotle and Leibniz on this point, as does Herbert Spencer, among contemporary English empiricists. And, with his characteristic frankness, even John Stuart Mill has recognised, in his work on Hamilton, that the rejection of substance as the bearer of phenomena is not entirely free from difficulties and uncertainties, especially in the mental realm. If, then, the new definition of psychology were connected with the new metaphysics just as inseparably as the old definition was with the old, we would be forced either to look for a third definition, or to descend into the fearful depths of metaphysics.
Happily, the opposite is true. There is nothing in the new definition of psychology which would not have to be accepted by adherents of the older school as well. For whether or not there are souls, the fact is that there are mental phenomena. And no one who accepts the theory of the substantiality of the soul will deny that whatever can be established with reference to the soul is also related to mental phenomena. Nothing, therefore, stands in our way if we adopt the modern definition instead of defining psychology as the science of the soul. Perhaps both are correct. The differences which still exist between them are that the old definition contains metaphysical presuppositions from which the modern one is free; that the latter is accepted by opposing schools of thought, while the former already bears the distinctive mark of one particular school; and the one, therefore, frees us from general preliminary researches which the other would oblige us to undertake. Consequently, the adoption of the modern conception simplifies our work. Furthermore, it offers an additional advantage: any exclusion of an unrelated question not only simplifies, but also reinforces the work. It shows that the results of our investigation are dependent on fewer presuppositions, and thus lends greater certainty to our convictions.
We, therefore, define psychology as the science of mental phenomena, in the sense indicated above. The preceding discussion should be sufficient to clarify the general meaning of this definition. Our subsequent investigation of the difference between mental and physical phenomena will provide whatever further clarification is needed.
3. If someone wanted to compare the relative value of the scientific field which we have just described with that of the natural sciences, using as a measuring stick only and exclusively the interest aroused at the present time by these two types of investigations, psychology would undoubtedly be overshadowed. It is a different matter if we compare the goals which each of the two sciences pursue. We have seen what kind of knowledge the natural scientist is able to attain. The phenomena of light, sound, heat, spatial location and locomotion which he studies are not things which really and truly exist.' They are signs of something real, which, through its causal activity, produces presentations of them. They are not, however, an adequate representation of this reality, and they give us knowledge of it only in a very incomplete sense. We can say that there exists something which, under certain conditions, causes this or that sensation. We can probably also prove that there must be relations among these realities similar to those which are manifested by spatial phenomena shapes and sizes. But this is as far as we can go. We have no experience of that which truly exists, in and of itself, and that which we do experience is not true. The truth of physical phenomena is, as they say, only a relative truth. The phenomena of inner perception are a different matter. They are true in themselves. As they appear to be, so they are in reality, a fast which is attested to by the evidence with which they are perceived. Who could deny, then, that this constitutes a great advantage of psychology over the natural sciences?
The high theoretical value of psychological knowledge is obvious in still another respect. The worthiness of a science increases not only according to the manner in which it is known, but also with the worthiness of its object. And the phenomena the laws of which psychology investigates are superior to physical phenomena not only in that they are true and real in themselves, but also in that they are incomparably more beautiful and sublime. Colour and sound, extension and motion are contrasted with sensation and imagination, judgement and will, with all the grandeur these phenomena exhibit in the ideas of the artist, the research of a great thinker, and the self-dedication of the virtuous man. So we have revealed in a new way how the task of the psychologist is higher than that of the natural scientist.
It is also true that things which directly concern us claim our attention more readily than things foreign to us. We are more eager to know the order and origin of our own solar system than that of some more remote group of heavenly bodies. The history of our own country and of our ancestors attracts our attention more than that of other people with whom we have no close ties. And this is another reason for conferring the higher value upon the science of mental phenomena. For our mental phenomena are the things which are most our own. Some philosophers have even identified the self with a collection of mental phenomena, others with the substantial bearer of such a collection of phenomena. And in ordinary language we say that physical changes are external to us while mental changes take place within us.
These very simple observations can easily convince anyone of the great theoretical significance of psychological knowledge. But even from the point of view of practical significance - and perhaps this is what is most surprising - psychological questions are in no way inferior to those which occupy the natural sciences. Even in this respect there is hardly another branch of science which can be placed on the same level with psychology unless perhaps it is one which merits the same consideration on the grounds that it is an indispensable preparatory step toward the attainment of psychological knowledge.
Let me point out merely in passing that psychology contains the roots of aesthetics, which, in a more advanced stage of development, will undoubtedly sharpen the eye of the artist and assure his progress. Likewise, suffice it to say that the important art of logic, a single improvement in which brings about a thousand advances in science, also has psychology as its source. In addition, psychology has the task of becoming the scientific basis for a theory of education, both of the individual and of society. Along with aesthetics and logic, ethics and politics also stem from the field of psychology. And so psychology appears to be the fundamental condition of human progress in precisely those things which, above all, constitute human dignity. Without the use of psychology, the solicitude of the father as well as that of the political leader, remains an awkward groping. It is because there has been no systematic application of psychological principles in the political field until now, and even more because the guardians of the people have been, almost without exception, completely ignorant of these principles, that we can assert along with Plato and with many contemporary thinkers that, no matter how much fame individuals have attained, no truly great statesman has yet appeared in history. Even before physiology was systematically applied to medicine, there was no lack of famous physicians, as shown by the great confidence they won and by the astonishing cures attributed to them. But anyone who is acquainted with medicine today knows how impossible it would have been for there to have been a single truly great physician prior to the last few decades. The others were all merely blind empiricists, more or less skilful, and more or less lucky. They were not, and could not have been what a trained and discerning physician must be. Up to the present time the same thing holds true of statesmen. The extent to which they, too, are merely blind empiricists is demonstrated every time that an extraordinary event suddenly changes the political situation and even more clearly every time one of them finds himself in a foreign country where conditions are different. Forsaken by their empirically derived maxims, they become completely incompetent and helpless.
How many evils could be remedied, both on the individual and social level, by the correct psychological diagnosis, or by knowledge of the laws according to which a mental state can be modified ! What an increase in mental power mankind would achieve if the basic mental conditions which determine the different aptitudes for being a poet, a scientist, or a man of practical ability could be fully ascertained beyond any doubt by means of psychological analysis! If this were possible, we could recognise the tree, not from its fruit, but from its very first budding leaves, and could transplant it immediately to a place suited to its nature. For aptitudes are themselves very complex phenomena; they are the remote consequences of forces whose original activity suggests these consequences no more than the shape of the first buds suggests the fruit which the tree will bear. In both cases, however, we are dealing with relationships that are subject to similar laws. And just as botany can make accurate predictions, a sufficiently developed psychology must be able to do the same. In this and in a thousand other different ways, its influence would become most beneficial. Perhaps it alone will be in a position to provide us the means to counteract the decadence which sadly interrupts the otherwise steadily ascending cultural development from time to time. It has long been noted, and correctly so, that the often used metaphorical expressions, "old nation," and "old civilisation," are not strictly appropriate, because, while organisms only partially regenerate themselves, society renews itself completely in each successive generation; we can speak of peoples and epochs becoming sick, but not old. There are, however, such sicknesses which have always appeared periodically up to now, and which, because of our lack of medical skill, have regularly led to death. Hence, even though the really essential analogy is missing, the similarity to old age in external appearance is undeniable.
It is apparent that the practical tasks I assign to psychology are far from insignificant. But is it conceivable that psychology will ever really approach this ideal? Doubt on this point seems to be well-founded. From the fact that up to now, for thousands of years, psychology has made practically no progress, many would like to believe that they are justified in concluding with certainty that it will also do little in the future to further the practical interests of mankind.
The answer to this objection is not far to seek. It is revealed by a simple consideration of the place which psychology occupies in the system of sciences.
The general theoretical sciences form a kind of hierarchy in which each higher step is erected on the basis of the one below it. The higher sciences investigate more complex phenomena, the lower ones phenomena that are simpler, but which contribute to the complexity. The progress of the sciences which stand higher in the scale 9 naturally presupposes that of the lower ones. It is, therefore, evident that, apart from certain weak empirical antecedents, the higher S sciences will attain their development later than the lower. In particular, they will not be able to reach that state of maturity in which they can meet the vital needs of life at the same time as the lower sciences. Thus we saw that mathematics had long been turned to practical applications, while physics still lay dozing in its cradle and did not give the slightest sign of its capacity, subsequently so brilliantly proved, to be of service to the needs and desires of life. Similarly, physics had long attained fame and multiple practical applications when, through Lavoisier, chemistry discovered the first firm basis upon which it could stand, in the next few decades, in order to revolutionise, if not the earth, at least the cultivation of the earth, and with it so many other spheres of practical activity. And once again, chemistry had already achieved many splendid results while physiology was yet to be born. And it is not necessary to go back too many years to find the beginnings of a more satisfactory development in physiology, and attempts at practical application followed immediately. They were incomplete perhaps, but nonetheless served to demonstrate that only from physiology is a re-birth of medicine to be expected. It is easy to explain why physiology developed so late. The phenomena it studies are much more complex than those studied by the earlier sciences and are dependent upon them, just as the phenomena of chemistry are dependent upon those of physios and the phenomena of physics are dependent upon those of mathematics. But it is just as easy to understand, then, why psychology has not borne more abundant fruit up until now. Just as physical phenomena are under the influence of mathematical laws, and chemical phenomena are under the influence of physical laws, and those of physiology under the influence of all these laws, so psychological phenomena are influenced by the laws governing the forces which shape and renew the bodily organs involved. Consequently, if someone knew from direct experience absolutely nothing about the state of psychology up to the present time, and were acquainted only with the history of the other theoretical sciences and with the recent birth of physiology and indeed even chemistry, he could affirm, without in any way being a sceptic about psychological matters, that psychology has achieved nothing as yet, or that it has achieved very little, and that at best it is only recently that it has shown a tendency toward a more substantial development. This implies that the most important fruits which psychology may bear for practical life, lie in the future. So, should this person turn his attention to the history of psychology, he would merely find in its barrenness confirmation of his expectations; and he would find himself in no way committed to an unfavourable judgement as to its future accomplishments.
We see that the backward condition in which psychology has remained appears to be a necessity, even if we do not doubt the possibility of a rich development in the future. That there is such a possibility is shown by the promising, though weak, beginning it has already in fact made. Once a certain level of its possible development has been reached, the practical consequences will not fail to materialise. For the individual and even more for the masses, where the imponderable circumstances which impede and promote progress balance each other out, psychological laws will afford a sure basis for action.
We may, therefore, confidently hope that psychology will not always lack both inner development and useful applications. Indeed the needs which it must satisfy have already become pressing. Social disorders cry out more urgently for redress than do the imperfections in navigation and railway commerce, agriculture and hygiene. Questions to which we might give less attention, if it were up to us to choose, force themselves upon everyone's attention. Many people have already seen this to be the most important task of our time. We could mention several great scientists who are devoting themselves, with this end in view, to the investigation of psychological laws and to methodological inquiries concerning the derivation and confirmation of conclusions to be applied in practice.
It cannot possibly be the task of political economy to put an end to the present confusion and to re-establish the peace in society which has been increasingly lost amid the clash of conflicting interests. Political economy has a role to play, but neither the whole task nor the major part depends upon it. And indeed even the growing interest which is being accorded to it can serve to corroborate these statements. In the introduction to his Principles of Political Economy, John Stuart Mill has touched upon the relation between this science and psychology. The differences in the production and distribution of goods by different peoples and at different times, in his opinion, would depend to a certain extent on differences in the states of their knowledge of physical matters, but would also have psychological causes. "Insofar as the economic condition of nations turns upon the state of physical knowledge," he continues, "it is a subject for the physical sciences, and the arts founded on them. But insofar as the causes are moral or psychological, dependent on institutions and social relations or on the principles of human nature, their investigation belongs not to physical, but to moral and social science, and is the object of what is called Political Economy."
It seems beyond doubt, therefore, that in the future - and to a certain extent perhaps the not too distant future - psychology will exert a considerable influence upon the practical aspects of life. In this sense we could characterise psychology, as others have already done, as the science of the future, i.e. as the science to which, more than any other, the future belongs; the science which, more than any other, will mould the future; and the science to which, in the future, other sciences will be of service and to which they will be subordinate in their practical application. For this will be the position of psychology once it reaches maturity and is capable of effective action. Aristotle called politics the master art to which all others serve as subsidiaries. As we have seen, however, in order to be what it should be, it is necessary that politics pay heed to psychology, just as the lesser arts must heed the teachings of natural science. Its theory, I would like to suggest, will merely be a different arrangement and further development of psychological principles directed toward the attainment of a practical goal.
We have advanced four reasons which appear to be sufficient to show the outstanding importance of the science of psychology: the inner truth of the phenomena it studies, the sublimity of these phenomena, the special relationship they have to us, and finally, the practical importance of the laws which govern it. To these we must add the special and incomparable interest which psychology possesses insofar as it instructs us about immortality and thus becomes, in another sense, the science of the future. The question concerning the hope of a hereafter and our participation in a more perfect state of the world falls to psychology. As we have noted, psychology has already made attempts to solve this problem, and it does not seem that all its efforts in that direction have been without success. If this really is the case, we have here, without doubt, its highest theoretical achievement, which would be of the greatest practical importance as well, besides lending new value to psychology's other theoretical achievements. When we depart from this life we separate ourselves from all that is subject to the laws of natural science. The laws of gravitation, of sound, of light and electricity disappear along with the phenomena for which experience has established them. Mental laws, on the other hand, hold true for our life to come as they do in our present life, insofar as this life is immortal.
So Aristotle had good reason for placing psychology above all the other sciences, as he did at the beginning of his treatise On the Soul, even though in so doing he took into consideration its theoretical advantages exclusively. He says,
Holding as we do that, while knowledge of any kind is a thing to be honoured and prized, one kind of it may, either by reason of its greater exactness or of a higher dignity and greater wonderfulness in its objects, be more honourable and precious than another, on both counts we should naturally be led to place in the front rank the study of the soul.
What undoubtedly causes surprise is the fact that Aristotle here asserts that even with respect to its exactitude psychology is superior to the other sciences. For him the exactitude of knowledge is bound up with the imperishability of the object. According to him, that which changes continuously and in every respect evades scientific investigation, whereas that which is most permanent possesses the most abiding truth. Be that as it may, we, too, cannot deny that the laws of psychology at least possess a permanent important truth.