# Avenarius and the Standpoint of Pure Experience/The Description of Experience
## THE DESCRIPTION OF EXPERIENCE
### I

Pure experience means mere experience, experience just as it comes, consisting of things, thoughts and relations, and these consisting of it. It is not conceived subjectively nor does it presume any particular metaphysic of an objective reality. It is the simple presence or absence of whatever is empirically present or not present. And as we are in this discussion concerned with cognitive experience, by pure experience we shall mean experience characterized as the immediate cognition of facts, which facts may be things or relations, thoughts, feelings, convictions or uncertainty.
Avenarius gives a long list of examples of experience, and although some account was given above of his way of describing experience, a few illustrations from his own pages may serve to introduce a consideration of his general undertaking: "It is an experience that the sun shone yesterday, that it was obscured on the day before, that a recent year was perhaps an unusually rainy one, or perhaps unusually dry. . . . Among people of primitive culture an individual will declare it his experience that the moon, in case of an eclipse, is holding her child in her arms, that one visits distant places in sleep, that a shadowy being with a character something like a breath (hauchartig) is the source of feeling and movement in the body; and that a body can exist with a soul or without it, and that a soul can exist both embodied and disembodied. Stages of culture not so far from our own have the experience that shrieking drives away the monster that darkens the sun, and that incantations drive out the evil spirit which has entered into a body. In our own civilization, the demented patient experiences the command of God to throw himself out of the window,—he will fly like a bird [if he does so]."
A list like this could be prolonged indefinitely, but its significance is apparent from a few examples. Every such case of experience is a case of insight. The person who has the insight is not aware that he contributes anything toward the construction of what he perceives. He is sure that he is not mutilating any facts. He reports the truth as he perceives it. The command of God, a bit of geometry, excursions of the soul, facts of chemistry or mechanics are all facts which are directly observed and reported. From our ​point of view some reports of experience may be true reports of fact while others are not, but this is to say that experience is not necessarily valid experience. And the charge of incorrect observation must always be a character of another experience.
Now this cognitive experience can be made the object of scientific study. To say that an explanation of cognitive experience must be wholly futile because the judgments which state the explanation will themselves express only other cognitive experience is to misunderstand the purpose. The real effort in a psychophysical account of pure experience is not so much to get back of pure experience, as to get a larger acquaintance with it— to extend cognitive experience so as to include judgments about cognitive experience itself. Of course we explain cognitive experience by reducing it to cognitive experience, but this is our way of getting a fuller and richer cognitive experience. Whether we employ psychophysical concepts or mere introspection is a question of method. Because psychology makes extensive use of psychophysical concepts, and speaks of an outer world as the source of stimuli, psychology is not therefore metaphysics. Psychology has its point of view and its favorite method. Its data are observed data. Its aim is to observe other data. Any instruments which lead to richer observations are legitimate, and do not commit the psychologist to a metaphysic just because the aim is to come around again to another observation, and not to rest in the concept of an ultimate ground of phenomena which can not be observed.

## II

This, however, is the distinction between description and explanation as ultimate goals. We may say that the aim of science is the widest possible acquaintance with phenomena, where the word phenomena does not imply the metaphysical distinction of appearance and reality. Methods of observation appropriate to different regions of phenomena, and points of view for the apperception and orderly synthesis of phenomena, are developed. In the course of this work of observation and description various points of view are elaborated which have the function of explaining phenomena rather than of synthesizing and describing them, although both explanation and description may be accomplished. A point of view which both explains and describes is the principle of evolution. A point of view which as yet can be said only to explain is the reference of mental states to physical processes in the brain as the ground of consciousness. This latter point of view it is which has brought forth the much-discussed concept of psychophysical parallelism. At the risk of digression, a brief orientation on this concept will clear the ground for considering the application which Avenarius has made of it in his 'Kritik der Reinen Erfahrung.'
​We know of course that a great deal of consciousness depends upon brain-conditions. If we could make out these brain-conditions for given mental states, we should, to the extent we had done so, succeed in explaining the latter. We are able to explain many phenomena of consciousness in a general way. It is an explanation, though a very incomplete one, to say that a sufficient blow on the head puts an end to consciousness, to say that the sensations of sight or hearing or the power of speech can be eliminated by accidents of a given type to the brain. Well,—explanation is interesting. No one is obliged to take explanatory points of view if he does not wish to explain, but if he cares for the explanation of mental states he must assume that they are explainable. lie must look for causal connections wherever they can be found, and not conclude that on the whole he will not look for causal connections in precisely the region where, to a certain extent, they leap at the eyes.
Just why certain physical processes should have phenomena of consciousness as sequences no one pretends to say,—but the same mystery exists in all caudal relations. If one ask why the stream of consciousness continues to flow, why it didn't stop a minute ago instead of keeping on, one can only say it is because the heart con tinues to beat, the blood to circulate, and the brain to function. One can ask, if one has the courage, why the earth doesn't stop in its orbit, or why the sun doesn't stop shining. The fact simply is that consciousness keeps on in its dramatic and picturesque career, and if we wish to explain some details of that career, we look for laws of regularity between antecedent and consequent, and we assume, as a point of view that clears the ground and simplifies the problem, that consciousness is explainable in all respects, so far as the facts themselves are concerned. And whether one talks of antecedent and consequent or of parallel states seems hardly to matter at all.
In consciousness, such phenomena as the noon whistle of a neighboring factory, the sound of a man shoveling coal, a bicycle-bell, a piano across the street, the rattle of a wagon, may follow one after another. All sorts of sensations are continually starting up in consciousness in the most chaotic fashion. Any causal connection between them is out of the question. But this means that if sensations are explainable at all, they are explainable by something that is conceived as consisting of something else than psychic states. But if the mental states are conceived as depending upon physical states, and these latter as causally related, we get the mental states indirectly into a real series, and get rid of chance.
This is a point on which psychologists have done a good deal of hedging, no doubt because psychology is still open to the suspicion ​of entertaining metaphysical motives. Wundt will not admit any causal connection between the physical and psychical series; each seems to flow on regardless of the other, but somehow bound to take notice of the other after the fashion of a preestablished harmony. His article, 'Ueber psychische Causalität,' etc., is a polemic against what he calls the materialistic psychology, in which a causal relation is assumed between physical states and states of consciousness. I really see no reason why one should not be frankly and outspokenly materialistic in a natural science. It is understood that the question about ultimate reality is not raised at all, and until this question is raised there is no metaphysic.
But it certainly comes to the same thing in science to say that a physical state is the universal antecedent, or the universal concomitant, or the cause of a given mental state. When consciousness is disordered because of an observable accident to the brain, one says the condition of the brain thus introduced is the cause of the disordered consciousness. There seems no more purpose in speaking of it as a merely parallel physical state which is, however, not a cause of a mental state, than to speak of a stroke of apoplexy and the bursting of a blood-vessel as parallel physical states, but not to be taken as causes of changes in consciousness. Epistemology and the higher criticism of concepts may ask in what sense the word 'cause' is here used, but if the psychologist can say that without the physical state, the mental state would not have occurred, he has enough ground for using the word 'cause' in a frank and practical way. But in doing so he will be raising no question about reality, he will simply be assuming that his phenomena are explainable by causal relations.
Thus the relations which the psychophysical point of view assumes are relations for the purpose of explanation, but it is an explanation within the limits of phenomena, and no metaphysical implications are permitted. The explanation is not an ultimate explanation; the triumph of the point of view would be to be brought around again into the mental series, to be able to predict the mental states from the physical ones. That is, the triumph would lie not in an explanation, but in a description, and this hope, this possibility it is which makes explanations important parts of scientific undertakings. The explanation which confessedly is no help to a new observation may be interesting, but it hardly seems important. And if it helps to a new observation it fulfills its function, whatever its concepts may be. There may indeed be a metaphysical concept of psychophysical parallelism, such a doctrine as that of Spinoza, for ​instance, but when the concept appears in psychology to-day, the presumption is that it is a point of view for the work in hand.
As an illustration of psychophysical parallelism on a very elaborate scale and of the distinction between description and explanation, I purpose to go somewhat at length into the principle work of Richard Avenarius, his 'Kritik der Reinen Erfahrung.' I am the more disposed to this undertaking since Avenarius has. it seems to me, been very generally misunderstood, and I think unjustly.

### III

I will say at once that the aim of the 'Kritik der Reinen Erfahrung' is to be a contribution to natural science, and that it is not a system of metaphysics. The interest that it appeals to is primarily the interest in psychology; it appeals also to the interest in sociology and history.
That it should not have been so understood is explicable enough. The title reminds us of Kant. A 'Kritik der Reinen Erfahrung' must, one thinks, have a good deal in common with the 'Kritik der Reinen Vernunft.' Also, the author was a professor of philosophy at Zurich; his earlier works were a monograph on Spinoza and an attempt to define philosophy as the effort to conceive the world according to a mechanical principle. His later work, 'Der Menschliche Weltbegriff,' had a good deal to say about idealism, and he himself was the editor of one of the principal philosophical quarterlies.
In view of these facts, one took up the 'Kritik der Reinen Erfahrung' expecting to find, if not positive metaphysics, at least a criticism of metaphysical concepts. If we add to this a disposition to skip the notes in fine print, we have reasons enough for misunderstanding the work before us.
A remark which Avenarius makes in a note is a good introduction to his point of view. "As we have learned," he says, "to think of the nourishment of organisms, of their recovery from injuries and sickness, of their adaptations to changes in their environment without the intervention of the soul, so we have now to learn to think of the so-called purposive changes in the central nervous system without calling in a soul (Geist) to help explain, a soul whose own psychic changes would have to be first explained."
We may like this point of view or we may not; it is, in either case, an important psychological point of view at the present time. Psychology seeks to describe those mental activities which are its subject-matter by formulating laws of their occurrence and in making out psychophysical relations wherever they can be found, and ​it is felt that it would be to give up the whole task to admit a principle of original and arbitrary energy as a factor in the explanation. We constantly hear that this is materialism, and for one who does not distinguish between science and metaphysics it is materialism. But that distinction should, in the light of present-day discussion, be fairly obvious.
Avenarius undertakes to write a psychology of the processes of knowledge. Whether his psychology is a good one is a point for psychologists to decide. The important thing for us to notice is that the 'Kritik der Reinen Erfahrung' is psychology.
There is at the outset a certain fund of information to build upon. Whatever our metaphysic may be, we 'know' in psychology that consciousness depends upon processes in the brain of some sort, that the nervous system is responsive to stimuli, that the whole body, and the nervous system as part of it, is constantly engaged in breaking down tissue, and is in need of appropriate nourishment and of periodical repose. We know that the organism and its parts are capable of exhaustion, and, within limits, of recovery from exhaustion. There is a teleological aspect of the reactions which the organism makes to a great many stimuli. This aspect it is which has given to the soul concept such a stubborn foothold in psychology. But though we are unable to make a psychological use of this concept, we may not, therefore, overlook the facts which it was intended to explain. We can observe, too, a certain rhythmical character in life as a whole and in many particular processes. The alternation of day and night occasions regular intervals of work and rest, with points of maximal vigor and fatigue, and transitions back and forth between them.
We are assured also that there is a region which we call the central nervous system which receives stimuli and determines reactions. We know, too, that the physiological system acquires habits and is capable of acquiring skill. These things depend upon processes of some sort in an organ, the brain, but upon what processes in particular we know hardly at all.
Can we conceive an organ of such a type as to account for enough of such phenomena as to make it a useful concept for psychological purposes? Avenarius thinks we can, and he proceeds to describe a central nervous system with such characters as would explain, he thinks, a great many phenomena in a psychological way.
Avenarius describes a way of apperceiving the central nervous system. Certain phenomena being given, there is wanted a concept to make them intelligible. Avenarius is, in so far, in the same position as the one who elaborates a system of atomic relations to account for chemical phenomena.
The central nervous system is called by Avenarius the System ​C. This designation is chosen for purposes of convenience, and for limiting,' the discussion of the system C to those characters which he wishes to lay stress upon. The system C appears to be really the brain, but the word brain has many associations and suggestions which Avenarius wishes to leave out of account.
The system C is conceived as situated in the world among objects, from which it receives stimuli of various sorts, to many of which the reaction is a cognition. The undertaking is chiefly a psychology of cognitive experience, and accordingly non-cognitive reactions are left out of account. Avenarius states the situation as follows:
"Let any part of our environment be in such a relation to human individuals that when the former is a.s8umed, the latter state an experience; 'something is experienced, something is an experience or is a product of experience, or depends upon experience.'"
The statements of experience are called E-values, the stimuli themselves are called R-values (Reiz). An E'- value depends directly not upon any R-value, but upon the system C, and any particular E-value is a consequence primarily of the constitution of C at the time when it gave expression to E.
Changes of some sort certainly take place in the brain. We say that tissue is broken down and built up. The process of wear and tear we believe to be due in great part, at least, to physiological excitations due to the world without. The rebuilding of tissue depends, we are sure, upon the blood-supply to the brain. We are familiar with feelings of exhaustion and of recovery of vigor, and we are reasonably sure that these feelings depend on corresponding conditions of the brain, and that between the condition which accompanies a loss of vigor and that which accompanies the feeling of restored vigor a series of states of the brain intervenes. We know also that there can be too much nourishment of the whole organism and presumably of the brain and we know that the excess can be worked off, that is, that a certain destruction of brain tissue brings back a normal condition of that organ, a point of balance between nourishment and work which we would preserve if we could. This ideal point of balance about which we seem continually to oscillate, Avenarius calls the 'Vitalerkaltiingsmaximum,' or the point of complete vital preservation. When that point is reached, the system C is in a state of stability. Such a point we do seem to pass and repass continually.
We may regard this condition of stability within C as the balance of two factors, one of them all those influences which make for the exhaustion of C, the other, the influences which make for the restoration and nourishment of C. The former of these, being the sum of ​the R-values which play upon C and stimulate it to reactions, Avenarius calls f(R). The other he calls f(S).
And since the stability of C means that these two opposing factors are equal to each other and therefore nullify each other, Avenarius expresses the situation by the equation f(R)=-f(S), or f(R)+f(S)=0, which means that the result of the cooperation of f(R) and f(S) is that the system C does not depart from stability.
But if, starting with the system C in stability, we vary either f(R) or f(S), then it will no longer be true that f(R)+f(S)=0. To the degree to which one of the factors has been altered, the system C has departed from a state of stability. There has ensued a 'Vital Difference' and this vital difference is the difference between f(R) and f(S). One of the two factors is more effective in its influence than the other, and the difference between the two opposed forces is the vital difference. Since one of the factors is regarded as negative as related to the other, the difference is thus expressed: f(R) + f(S) > 0. The equation f(R) + f(S) =0 signifies that the vital difference has a value of zero, while the equation f(R)+f(S) >0 signifies that the vital difference is greater than zero.
The system C, however, tends always to return to stability, and the process of return must be a process of annulling the vital difference. There is thus a transition from stability through a condition of instability characterized by the existence of a vital difference back to stability, where the vital difference is reduced to zero. This series of states from stability to stability, Avenarius calls a vital series.
The vital series as thus described is a series of changes in the system C. The reason for assuming such series of changes is that parallel series of conscious states can be observed. The process of attention is an example. We start from what we may call a condition of indifference, or rest, or stability, then something awakens our interest and we begin to attend to some sort of a problem. We continue in a state of indecision and doubt and perplexity, looking forward, however, toward the solution which we hope to find. At last the solution comes, and we are at peace with ourselves again.
Now if to the changes of consciousness there is a parallel series of brain-events, they must form a series, and since each term of the series must be adequate to its effect in consciousness, the physiological series may be described with reference to its dependent mental states, and its terms considered as bearing relations to one another similar to the relations and proportions in the consciousness series. This is not so empty or so metaphysical as it may sound. We take it for granted, in a general way, that of the changes in brain tissue ​which produce changes in consciousness, the greater the one change the greater the other. And although the one series of changes is quantitative and the other qualitative, we do speak of a more and less, and carry on a good deal of comparison in the region of qualities. We have, in any case, a physiological series, and dependent upon this a series of mental states, or rather we have a continuous nervous process and a continuous stream of consciousness depending upon the former, and these continuous processes we can break up into parallel lengths, called vital series. The physiological series is called the Independent Vital Series, the series in consciousness is called the Dependent Vital Series.
It is unfortunate that the method of exposition chosen by Avenarius makes it appear superficially that the dependent vital series is deduced from the concept of the independent series, together with the general presuppositions, and that therefore nothing about the dependent series can be any better established than the concept of the independent series.
Obviously, however, the dependent series is a movement in consciousness which can be observed, and it is to account for these series of conscious states, which are data of experience, that the physiological series is assumed.
In the above case of an attention-process as a dependent vital series, three stages can be observed: first, the appearance of the problem, the awakening of interest and the consequent feeling of restlessness and dissatisfaction if the solution does not immediately appear. This is the 'Initial' stage; then comes the continued effort to solve the problem, the 'Medial' stage; and finally the appearance of the solution, characterized by satisfaction, abating anxiety, the settling down upon an opinion or a cognition. This is the 'Final' stage. Corresponding to these three stages of the dependent series are three stages of the independent series,—the appearance of the vital difference and a departure of the system C from stability, the continuance for a longer or shorter time with an approximately constant vital difference, and then the reduction of the vital difference to zero, with consequent return to stability.
The system C maintains itself by getting back to stability after disturbances. This functional activity can be performed in a way that is better or worse for the life of the system C itself, that is, we can conceive an ideal system C. Such an organ would, after any disturbance, return to stability with the shortest interval of a vital series. This would be accomplished if the system C were trained to recover stability by means of well-learned and completely habitual vital series, that is, if the system C by virtue of its liability to habit has learned to recover stability with maximum facility.
​Now we are sure that the nervous system is subject to habit, and that this is one of the factors which is most important in making life well organized, in simplifying the mental outlook, in making experience coherent and developing a consistent will. Our point of view obliges us, therefore, to assume a parallel physiological development.
Certain independent (physiological) vital series thus become habitual, and the functional excellence of the system C is in proportion as the fund of habitual series is adequate to all the reactions of the system. Such an 'eingeübte' series Avenarius calls a 'vital series of the first order.' Other series with a more or less novel character he calls 'vital series of a higher order.' Evidently the functional development of the system C lies in the reduction of series of higher orders to series of the first order. This means the gradual introduction of order into the behavior of the system C by means of its own education, if we may so describe it.
By habit we reduce the complex environment to its simplest terms. We learn to ignore large masses of it, or rather we react upon various manifolds according to certain constant characters or values which we find in them. If we translate this into physiological terms, it gives us a sort of physiological selection. The nervous system has become responsive to certain selected portions of its environment. That is, the education of the system C has been controlled by certain R-values to the exclusion of others. This concept of physiological habit is of the first importance in the theory of Avenarius, but it is so important because the fact of habit is of such great importance in life.
The consequence of habit is that experience becomes less and less diversified. All sorts of E-values no longer occur. In its effects upon experience, growth by habit is a process of exclusion, which, so far as the character of the system C is concerned, could go on indefinitely. It is a process by which the mind comes to give a final definite character to the manifold presented to it by the world, —a process by which a maximum experience of the world expresses itself in a resulting apperception of the world. This final apperception of the world depends upon the possession of a predicate which is applicable to every fact which experience testifies to as existent, and this means, in the terminology of Avenarius, that a final stage of the system C has been found by which any vital difference may be annulled. By virtue of its capacity for acquiring habits, the system C has found an answer to the question, 'What is everything?'
This idea of a limiting stage of the process of progressive determination of experience is, of course, only an idea, but it is not, ​therefore, an insignificant idea. It is the concept of the natural limit of that kind of process which we are perfectly familiar with as habit.
It is easy to get the impression that every vital series must be started by an outer R-value. This, however, is not the case. If we recall the formula for stability, f(R)+ f(S) =0, we perceive that a vital series can be initiated by a variation of f(S) as well as of f(R).
The system C is, after all, the brain,—blood is being constantly supplied to it and its own complex constitution and energy must be a continual source of instability.
A judgment is an E-value. Judgments accordingly follow the same law of habit that all E-values follow. There is a progressive exclusion of possible judgments, a progressive definition of experience in the narrower sense, an evolution of pure experience by virtue of the law of habit. It is this evolution of pure experience in which Avenarius is primarily interested.
One has only to compare different civilizations and stages of culture to observe that the world may contain for one race and for one time very different objects of experience from those which it contains for another race or another time. Our own way of experiencing the world is certainly the outcome of an evolution. The discussion about possible objects of experience in the first section of this paper sought to make clear that almost anything can be an object of experience. We conceive of our experience to-day as being very much more valid, more adjusted to the facts of nature, more 'scientific' than the experience of our ancestors a few centuries back.
"We are disposed to think that we have awakened from credulity and superstition, and that we look out upon the world with a sane and critical observation. Perhaps we do, but it is interesting to note that experience has come to be what it is for the man of science among us as the result of the continual modification of a primitive and wholly uncritical experience.
About that primitive experience we, of course, know very little, but there is reason enough to suppose that it had a decidedly 'animistic' character. In that primitive stage of culture in our own prehistoric past no doubt many things could be objects of experience which could not be objects of our experience. There has been a progressive elimination of certain objects of experience, and a progressive enrichment of experience by the acquisition of other objects. When we are in an imaginative mood we sometimes lament that nature has lost for us the vivifying presence of the gods of the soil, the groves and the streams. But in a rationalizing mood, we say that we no longer introject into nature the likeness of ourselves. ​We hold that our concept of nature is a valid concept, the product of critical and unbiased observation. Translated into the language of Avenarius, this means that our E-values correspond to our R-values. We say about nature only what she says about herself. The E-values which express primitive animistic experience are certainly decidedly different in some respects from those E-values which express the experience of a Helmholtz or a Huxley. Yet they are alike in being all E-values. Whether justly or not, we do speak of an enlightened scientific experience and contrast it with one that is relatively superstitious, and the enlightened experience, as well as the other, has its roots in that primitive experience which we may suppose to have been absolutely imaginative and credulous.
But few of us are accomplished men of science. Not every one has moved so far from the starting-point. And yet we may say that there is a large group of minds that take what we may call the scientific point of view, whose experience does not include mythological objects. Other minds, those that make up the great majority in our own civilization, while not distinguished by very consciously scientific points of view, do yet have an experience, more resembling the experience of a scientific mind than that of the primitive animistic mind. Yet there still remain, Avenarius thinks, some traces of the original fund of animistic objects. The further development of this idea, the description and criticism of the remnant of animism, has for Avenarius a special polemical interest, which would lead us too far aside to follow up. What Avenarius would have us observe is that the evolution of experience is still in progress, and that what lies ahead must be a continuation of what lies behind. The progress thus far has been the development of that concept of nature which natural science has come to regard as the proper one, and the very general elimination of animism. The continuance of the same process should mean the complete elimination of animism, making the modern concept of nature wholly consistent and the complete acceptance of the world so defined as an object of experience.
All this history of experience can be made the matter of a psychological study which should seek to describe the process from a psychophysical point of view. This is what Avenarius has done.
The line of thought by which Avenarius himself approached this problem helps somewhat to throw light on the definition of the problem itself as Avenarius understood it. Avenarius has expressed great indebtedness to Mach, and his approval of the latter's 'Principle of Economy.' Mach has stated this principle in the following terms: "Science itself, therefore, may be regarded as a minimal problem, consisting of the completest possible presentment of facts ​with the least possible expenditure of thought." That is, the aim of science is to give such a conceptual description of experience as shall be most comprehensive and readily intelligible.
"With this in mind let us make science the object of a psychological inquiry. It seems evident enough that the mind is an instrument for accomplishing purposes. It makes a difference to the organism whether the mind functions well or ill. But in attributing this teleological value to the mind, we have demanded two things. Not only must there be an organ to function in a purposive way, but this functioning must be carried out as well as the given conditions make possible. Other things being equal, that functional adjustment will be the best one which is made with the least expenditure of energy.
This may sound like an effort to translate psychology into pseudo mechanics, but I think there is really no mystery. No one would deny, I fancy, that, other things being equal, that adjustment of the organism is the best which is least exhausting to it. Vital energy, whatever that may be or depend upon (and I do not wish to imply any unique 'vital force'), is finite in quantity, so that it makes a great deal of dift'erence whether our energy is wasted or not. But if we banish the concept of a 'vital force' and mean by force only what is meant in mechanics, and then undertake to give a psychophysical account of the way in which Maeh's 'Principle of Economy' works, remembering that the idea of mechanical force is due to the sense of effort and energy in experience, it seems not inappropriate to find the mechanical equivalent of the principle of economy in the principle of least resistance. Accordingly, an early essay by Avenarius is entitled, 'Philosophy as Conceiving the World according to the Principle of Least Resistance. '
It may perhaps be said that this is an attempt to describe science itself as the line of least resistance, whereas science means effort, the expenditure of force. How much less is the effort involved in being indifferent to scientific problems! The man who cares nothing for science is, other things being equal, more economical, as regards his energy, than the eager scientist. Science is not, this view would hold, the line of least resistance, but a line of very great resistance.
This objection is, however, not so well founded as it seems to be at first glance. We find ourselves with a large program of theoretical interests on our hands. These interests are more or less lively attitudes on our part. We find ourselves responding to what interests us. We can not put the problems aside and be indifferent to them; they haunt us, and demand our attention, I am speaking, of course, of the men who care for problems, of the men who have ​made science and philosophy and are making it. The need of solving a problem is a real practical need. How much science should we at present have if there had not been a large amount of that human restlessness, which we call interest, on matters of theory.
This scientific uneasiness depends upon a capacity for discovering problems and being worried by them. The presence of some unexplained, uncomprehended thing is a cause of effort, of striving, of using up energy. The energy is expended for a purpose, the solving of the problem; and of various solutions that may offer themselves that one is accepted as the best which calls for the smallest expenditure of energy. The elegant demonstration is the one which makes use of few resources. Clearness and transparency of method and result mean usually that relatively little effort is needed to understand them.
Let us admit then, for the purpose of this discussion, that the principle of economy is the guiding principle in science, and that the principle of least resistance is its parallel principle in nerve-tissue.
Every special science seeks to get what it might call a valid experience of its objects, and this means that it tries to get the objects pure and uncontaminated by any personal equation. No doubt the principle of economy leads, to a certain extent, to a misrepresentation of objects, but this is the ignoring of what is regarded as irrelevant from the point of view of the special interests, whereas a subjective enrichment of the object is the putting into it of what might make a difference in the description. This much seems clear, science feels at liberty to ignore as much detail in the objects as it is not interested in, but it denies the right to add anything.
Now if we admit that the special sciences are seeking to get their objects pure and if we imagine that there is a special science for each region of phenomena, and if we call this experience of pure objects a pure experience, then the special sciences are collectively aiming at a pure experience of the world.
This was the meaning of pure experience as Avenarius used the term in his 'Philosophic als Denken der Welt Gemass dem Princip des Kleinsten Kraftmasscs, ' and it is one of the meanings of the term in the ' Kritik der Reinen Erfahrung. ' But since such a pure experience is defined from an epistemological and not from a psychological point of view, the concept does not appear in the same form in the later work.
The special sciences are distributed, each to its own field. Within each field, novel facts are comprehended by reducing them to a group of known facts, which group undertakes to be as small as possible. In the same way the effort to understand the world would be the ​effort to reduce to a single concept the characters, common to the pure experience, which the special sciences are able to secure. This effort, based upon the special sciences, to describe the common character of the whole world, is, says Avenarius, philosophy. It is the effort to answer the question. What is everything? With so much in mind, we are prepared to understand the following quotation: "In accordance with the principle of least resistance there is accomplished the reference of a single presentation to a general concept, and in so far as this presentation is strange and novel it is made known by this reference. Accordingly, conceptual understanding is a force-economizing, theoretical apprehension of an object, and the totality of objects will be most economically conceived, if they can be apprehended under one general concept. This effort to conceive the totality of objects with the minimum expenditure of force is philosophy. The all-comprehending concept must state what is common to all particular objects. This common aspect mast be given in pure experience. Individual cases of pure experience are secured by means of observation in the special sciences, and the purification of experience, in general, results from the elimination of what is found to not really belong to the objects of experience."
It may appear that we are getting a good way from the system C and its vital series. The digression has its purpose, however, in that it will help us to understand the way in which Avenarius himself viewed his problem, by seeing that problem in its earlier stages. Let us now connect the essay we have just been considering with an article by Avenarius entitled 'The Relation of Psychology to Philosophy.' In the essay just considered, Avenarius describes philosophy as a certain kind of human effort, the effort to get a unified conception of the universe, to ask the question, What is everything? and to tell what it is.
This question, What is the nature of the world ? How is the world constituted? is the question of philosophy. When this question is first asked, there is no doubt concerning our power to know how the world is constituted if we can only find it out. At the same time, psychology contributes little or nothing in giving shape to philosophy. Psychology hardly exists as an independent field, but forms a chapter in some system of metaphysics. The fate of metaphysical systems, however, contradictions discovered within and without, made the problem of knowledge more and more prominent, so that instead of the question. How is the world constituted? we have the question, How is the world known? When this question is first ​critically asked reality is still attributed to objects which lie outside of experience, but great emphasis is laid upon the subjective factor in knowledge. It is taken for granted that perception does not give an object as it really is, that the whole content is not given in perception, but, on the other hand, it is assumed that the whole content given in perception does not really belong to the object. Objective reality is thus, at the same time, more and less than experience.
The original question, How is the world constituted? demands now a distinction between what can be taken as valid experience of objects and experience which misrepresents its objects. By this emphasis laid upon the problem of knowledge, and the recognition that the mind is so constituted as perhaps to interfere with its own cognitive purposes, psychology becomes of decided importance for philosophy, and it is not long before the world of real objects shrinks to a region of things in themselves, set over against forms of experience. It is a matter of recent history how the content of the world, which seemed to be lost on the objective side, was brought back from the subjective side, and how from this point of view the great systems of idealism grew up. But whether deservedly or not, those systems have fallen into disrepute, one factor in this situation being the progress of physical science. And to-day if one asks how we know the world, the scientist will point to his instruments for observation and experiment and say, * With these we know the world.'
But knowledge secured by the aid of instruments for exact measurement is not the less subjective. Truer, perhaps, it would have been to say, 'By the use of these instruments do we conceive the world.'
The question, How is the world constituted? has become, provisionally at least, the question, How is the world conceived! And to this question one may now give a somewhat unexpected answer. The world is conceived by a nervous organism reacting in a certain way to its environment, and the question, How is the world conceived! becomes the question. How does this organism behave in conceiving the world? or, "What kind of a natural process is philosophy! Philosophy is a certain type of human activity, and if one agrees that activities of thought depend upon processes in nervous tissue, one has a ground for asking, as a scientist, what sort of natural process philosophy is.
Avenarius undertakes to carry out frankly the psychophysical point of view. He conceives that types of experience depend upon typical processes within an organ. The organ he afterwards called by the name of 'System C' and its processes he sought to describe as 'Vital Series.'
​This brings us back to the 'Kritik der Reinen Erfahrung,' but it brings us back prepared to observe the application of the method of the 'Kritik' to the description of philosophy as a natural process. If the question, 'How do we conceive the world?' in this new form can be answered with any measure of success, we may be able to reach some conclusions about the conditions on which the fate of systems of philosophy depends, and be able to state what conditions must be fulfilled by a philosophy which shall endure.
It was remarked above that the appearance of a problem means a certain restlessness on the part of him who sees the problem. We ought to distinguish between real problems and pretended problems. By real problems I mean questions that strike us as really problematic, questions whose solution one way or another makes a difference to us, questions which are problems not merely by virtue of a definition, but by virtue of the kind of interest they arouse. Besides the genuine problems there are problems which do not show any really problematic character. The problem about solipsism is a problem of this sort. A healthy man can not possibly find any real problem here. We may admit that the reality of other selves is problematic, but we shall be quite unable to experience the problematic character which we admit.
Progress in science and philosophy is largely due to a capacity for discovering real problems. Oriental peoples have this genius in a far less degree than Europeans. The problems of the Oriental consciousness are solved. Only the Western consciousness is tormented with doubts about reality, duty, the past and the future. Avenarius loves to dwell on the satisfaction and relief which the solution of a real problem affords, and on the teasing, restless, unsatisfied state which accompanies an unsolved real problem.
The distinction between the real problem and the artificial problem would appear to be a real and important distinction from the psychological point of view, where the purpose is an accurate description of experience. For this point of view, the so-called artificial problem is no problem at all. That is, its parallel brain-process can not be the one which gives rise to the problematic character. Accordingly, the word 'problem' will designate, in what remains to be said about Avenarius, always the real and genuine problem, the problem with the biological disturbance behind it. Evidently a philosophy which is to endure, which shall be, as Avenarius puts it, 'biologisch haltbar' must be an E-value or a group of E-values which express a permanent stability of the system C. These E-values have, in the process of physiological selection which marks the evolution of habit, come to prevail over other E-values. They have come to prevail because they represent the constant character of nature.
​We find an analogue of such a brain-condition in the accomplished man of the world. He is adjusted to all the situations he is liable to meet. Nothing surprises him or throws him out of composure. So long as the world remains the sort of place he has found it to be, he knows how to live in it, and how to adjust himself to its demands. And this attitude of adjustment is not a theoretical attitude; he does not have a theory about the world he knows; he has the certainty of reine Erfahrung. He has 'sized up' the world and knows what it is, and the world, as he understands it, is the world of his experience with nothing problematic about it. Such a final and definite comprehension of the world is, in the above case, evidently arrived at by a process of growth from something less mature, less aufgeklärt, and accordingly not well fitted to maintain itself in the face of a large and varied experience.
We have here an evolution of experience, and at the beginning we have a certain fund of convictions and experience and 'knowledge,' and at the end we have another fund of experience. Such a fund of experience Avenarius calls an 'Erkenntnissmenge.' Evidently the second Erkenninissmenge is obtained by a gradual modification of the first. In actual experience, we know well enough how this happens. The world does not correspond to our expectations and we have to make our expectations correspond to the world. But what Avenarius wants is a comprehension of just this process in psychophysical terms. And the process to be comprehended is not the history of an individual system C.
Whatever 'Weltbcgriff our remote ancestors may have had, it no doubt expressed their assurance about the world and not their doubts and problems concerning it. But, as we can observe, doubts and problems arose; the E-values of the Weltbegriff lost their qualities of existence, acquaintance and security, and became problematized. Or as Avenarius puts it, the 'world concept' turned into the 'world problem.' It was bound to do this, because the world had been conceived animistically by the imaginative projection into it of characters which it did not possess, while the system C has got to be formed by the real R-values and not by mythical ones.
But, as in the case of the man of the world, so here the goal of the process is the deliverance from illusion, the winning of a clarified idea of the world which is in accord with the facts. But, some will exclaim, what kind of a system C will that be which can have a history like this, beginning in the dim past and reaching into the future?
At this point I take leave to recall the social basis of the concept of validity. Validity as a fact in actual experience, as a character ​of actual judgments, depends upon social agreement. If only one, or only a very few astronomers had been able to see spots on the sun, the judgment 'there are sun-spots' would have had no validity in science. The crank with his hobby may conceivably be right all the time, but such validity as his judgments might possess is something different from the validity which characterizes accepted judgments.
Just as science is not the private possession of any one individual, so a primitive view of the world is share<l in common. But philosophical views of the world to-day can not be said to be held in common to any great extent. In so far philosophy is at a disadvantage as compared with science, for there is not enough agreement in philosophical judgments to give them the character validity.
We have thus a cooperation of different minds as the basis of validity. But from a psychophysical point of view this means the cooperation of different nervous systems, or a social system C. Such a system C as this can have a history which no individual could have. Avenarius calls such a system a 'Congregal System,' and represents it by the symbol ΣC.
Now it is easy to ridicule this concept, but it is unquestionably a perfectly legitimate one. It does describe the situation. The situation involves the psychophysical aspect of experience, the history and evolution of experience, and the fact that the education of an individual depends in the very highest degree upon his relations with other individuals, and that judgments about objective things derive their validity from social cooperation in these judgments.
It seems to me rather a proof of the value of the concept of the individual system C that it can be so readily extended to include all those individual systems which do determine one another in their judgments, and thus do really constitute a system.
By virtue of such a system as ΣC, the experience of one generation depends upon the experience of previous ones, and the process of eliminating the E-values which are not determined by R-values is made possible. These E-values which are to be got rid of represent the remnants of primitive animism, which was, of course, a falsification of nature by an imaginative introjective process. The heritage of animism which we have on our hands is, Avenarius thinks, the soul-concept and its consequences in philosophy.
The soul is conceived to be something within the body,—it is the basis of a literal distinction between inner and outer. The concept of the soul is, indeed, not prominent to-day, but the distinction between inner experience and outer experience, internal sense and external sense, is common enough. If there had been no soul-concept, the course of philosophy would no doubt have been very different from what it actually has been; it seems very probable that ​there would have been no Kantian theory of the categories, and that we should not have seen Schopenhauer announcing as the most obvious of truisms that the world is my representation. By thus explaining idealism as the final result of the soul-concept which was itself a bit of introjection left over from the original animistic reine Erfahrung, Avenarius includes it among the E-values which will be eliminated in the course of the history of ΣC, if that history is not interrupted.
As the subjective additions to nature are eliminated from our view of the world, we approach a purely descriptive concept. We no longer speak of the world of our experience as the phenomenal world, while the real world is something else, we know not quite what. The world we observe is accepted as the real world, precisely as the plain man accepts it. And if we ask what the whole world is, our answer to this question will seek to state what the whole world has in common as the object of our clarified experience which has at last got the world pure. The judgment about the whole world will then state merely what can be observed by any one, and not what is the product of the poetic imagination of a few,—as when one says, everything is a bit of one absolute experience. The final Weltbegriff will express a knowledge of genuine R-values only, which affect the peripheral nerves. This concept of nature being the product of maximum experience will not be liable to variation.
I think it is clear enough in a general way what Avenarius is trying to state, although it is not always clear in detail. We have a historical process, the evolution of experience. This historical process has, as its first stage, a view of the world, which if put into words would tell simply how nature is experienced. This Welthegriff describes what is reine Erfahrung. By constant variation the Weltbegriff comes to describe the world as it is not experienced. The actual experience of the world gives the lie to the 'critical* theory of it. The process approaches a Weltbegriff which describes the world as it is experienced. The experience which this view of the world asserts is an E-value and expresses such a 'final' state of the system C as can follow upon the presentation of any R-value.
As to the content of this E-value Avenarius can say only that it will be 'Vorgefundenes.' This may seem a poor outcome, but it means that the world is whatever it is observed to consist of. Trees are trees and houses are houses and clouds are clouds. They are not thoughts of God nor experience of the absolute nor phantasms of our own. There will be no effort to go behind what experience offers. Every single fact will be just this that we observe, the empirical fact before us. This is what Avenarius means by saying ​that the clarified and pennanent Weltbegriff will declare, 'Everything is this.' And is not this precisely the philosophy, or, if you prefer, the lack of it, of the 'plain man'? He it is that does full justice to the empirical diversity of the world. Science seeks to remove diversity by reducing things to common denominators. Metaphysics has not, since Aristotle at least, shown and disposition to recognize diversity. Possibly one should make an exception of Leibniz, but speaking generally, metaphysics has usually sought to absorb the empirical world with all its diversity and uniqueness into some form of an existent One, and there is much to suggest that this. One is the mystic ONE of Neo-Platonism.
But the 'plain man' never pretends that one thing is like another except for practical purposes. For him the common feature throughout the world is the fact that everything in it is a 'this.' And if one must ask the question 'Was ist alles?' one can answer from the point of view of pure experience only 'Alles ist dies. '
The 'Kritik der Reinen Erfahrung' really undertakes to describe the form of the evolution which our experience of the world has undergone and is still undergoing,—a form which might go along with one content or another. We should keep in mind that Avenarius is dealing with fact or with what we accept as equivalent to fact. We have the kind of experience that is expressed in what, following Avenarius, I have called 'the natural view of the world.' We have also the idealistic theory of reality, and this claims to be a scientific theory, and one which is more scientifically complete than any other metaphysic. But it describes reality in a way that obliges the man who does the actual work of making us acquainted with the world to assume a somewhat apologetic attitude.
We have also the fact that the actual idealism of history is a result of the fortunes of the idea of the soul and the idea of God, both of which must be assumed to have had entirely natural origins. This is, of course, no refutation of idealism, but it strengthens the presumption that something is wrong somewhere about the premises of idealism. The difficulty of making out just where the error lies may well be due to the fact that we are all bred up in the point of view which leads so logically into idealism. Avenarius saw on all hands a discontent with idealism, and I think it is fairly evident that this discontent has increased since Avenarius wrote, and is increasing. ​The key to the logic of the situation has not yet been found, although I think the first step toward finding it has been taken.
'The dualistic discontent,' as Avenarius calls it, expresses a desire to conceive the world in a way corresponding to our natural experience of it. In view of the continuity of experience, such an evolution as that described by Avenarius seems, then, extremely plausible, when once attention is called to it.
We can not cast off all at once habits of mind cultivated by centuries of faith; they bind us in ways we can not name. But the theological tradition is giving way, and in proportion as it does, we come more and more to feel that the truth about the world is to be found in a complete description of its empirical content. It seems not at all unlikely that the theological tradition will in time cease to affect metaphysics, and that in consequence metaphysics will no longer give the lie to common sense. Of the metaphysics of this third stage Avenarius says only that it will be 'biologisch haltbar.' He does not say it will be true.
If we are to understand by metaphysics the speculation which puts such stress on distinguishing 'appearance' from 'reality,' which defines reality as the source of appearance, a reality to some extent knowable but mostly unknowable, if metaphysics means this, Avenarius does seem to cast it ruthlessly overboard. As the task of philosophy he predicts that of stating the character common to all objects of experience. And for one who really occupies the pure experience position, and is not concerned with polemical attitudes toward any other, the common character of all objects of experience must be the most abstract, the most unimportant and the most uninteresting of predicates. Far more important and interesting will be what is concrete and actual.
To come back into the terminology of the 'Kritik der Reinen Erfahrung,' the final view of the world will express a knowledge of genuine R-values only such as affect the system C. This concept of nature being the result of complete determination by habit, will not be liable to change.
Of course it is not meant that this final Weltbegriff is necessarily going to be attained, but only that the process is of such a kind as to have this for its limit. The process may be interrupted by a catastrophe at any moment.

### IV

In the introduction to the 'Principles of Mechanics,' of Herz we find the following statement: "In endeavoring thus to draw inferences as to the future from the pant, we always adopt the following process. We form for ourselves images or symbols of external objects, and the form which we give them is such that the necessary consequents of the images in thought are always the images of the necessary consequents in nature of the things pictured. . . . The images of which we here speak are our conceptions of things. With the things themselves they are in conformity in one important respect, viz., in satisfying the above-mentioned requirement. For our purpose it is not necessary that they should be in conformity with the things in any other respect whatever." The concepts must be 'permissible,' that is, logically self-consistent; they must be correct, or not contradicted by experience; and they must be appropriate, that is, embody the 'principle of economy.'
Herz, thus, in agreement with Mach and Carl Pearson, describes the scientific concept as a construction of the investigator. It is an instrument with a function, that of leading to new observations and predicting sequences of phenomena.
This point of view is, however, radically opposed to the older view which defined its aim as the discovery of the real causes of observable phenomena. It was taken for granted that the phenomena of nature depended upon movements of matter,— and that matter in motion was a definite transcendent object of knowledge. The following from Helmholtz expresses this point of view. "The theoretical portion of physical science seeks to discover the unknown causes of events from their observable effects; it seeks to understand them according to the law of causality. We are forced to this task by the principle that every change in nature must have an adequate cause. . . . The final goal of the theoretical sciences is thus to discover the ultimate unchanging causes of changes in nature."
Herz himself at one time predicted that the great problem of physical science would be the nature and the laws of the space-filling ether. "It seems more and more probable that this question will take precedence of all others." 'Herz spoke then wholly committed to old preconceptions,' says Kleinpeter in the article from which I take the quotation; and it goes without saying that Herz ​had assumed a fundamentally different point of view when he wrote the 'Mechanics.'
Kirehhoff in the introduction to his 'Vorlesungen über Mathematische Physik' gives expression to the new point of view. He says: "The point of departure which I have chosen is not the ordinary one. It is customary to define mechanics as the science of forces, and forces as the causes which produce motion or strive to produce motion, . . . In the cause of the precision, which is, in other respects, characteristic of conclusions in mechanics, it seems desirable to get rid of ambiguous terms (Dunkelheiten) even if we are obliged to narrow the task of mechanics. I, therefore, propose, as this task, the description of the movements which occur in nature, a description as complete and as simple as possible."
One of the frankest statements that the scientific concept is a construction of the mind and not necessarily an image of transubjective things, is the prefatory note of Herz to book I. of his 'Mechanics.' It is as follows: "The subject-matter of the first book is completely independent of experience. All the assertions made are a priori in Kant's sense. They are based upon the laws of the internal intuition of, and upon the logical forms followed by, the person who makes the assertion; with his external experience they have no other connection than these intuitions and forms may have."
The second book contains the application of the system of concepts to the phenomena of experience. The contrast and relationship between volume I. and volume II. of the 'Kritik der Reinen Erfahrung' are almost identical with that between books I. and II. of the 'Mechanics' of Herz. Avenarius would not and could not claim that the concepts and definitions which fill volume I. are entirely a priori constructions. But they are psychological inventions for the purposes of scientific apperception, inventions, however, which are adapted to the phenomena. But the lines of procedure of Herz and Avenarius seem very similar. Herz described scientific method as the formation and use of images or sjinbols of external objects such that 'the necessary consequents of the images in thought are always the images of the necessary consequents in nature of the things pictured.' Now critics of Avenarius have complained of the dialectical way in which his 'Kritik' develops; but such a character is inevitable if there are to be any consequences of the symbol which shall be symbols of facts. Whether Avenarius has met with any success in this effort, whether his outcome is really a logical consequence of his symbol, or whether it could have been stated ​out any reference to a system C and its determination by recurrent vital series, is a decision which lies outside the present undertaking. I am disposed to believe that the results which Avenarius finally reached were won partly by means of his symbol. When we have all three groups, the concepts, the phenomena of experience and the final conclusions and statements, we can, perhaps, say that the latter group needed only the group of experience-facts to produce it. But if a group of concepts are of assistance of any sort in reaching conclusions, the concepts have served their purpose, whatever critics may think of them.
The efforts of Kirchhoff, of Herz, and I may say of Avenarius, show the effort to eliminate explanation from science as an ultimate goal, and to limit its task to description which shall be as simple and as complete as possible. But from this point of view it is not pretended that science is a statement of nature's eternal truths, and, as Kleinpeter observes, it follows that there is for humanity 'no objective truth enthroned above gods and men, as the ancient Greeks imagined.'
We admit readily the wisdom of this point of view, and yet some of us are sure to feel not quite satisfied. Science does well indeed to get rid of metaphysics, to accept its method as method and not as revelation. Yet a Veritas there must be, we say, and by what right does science forbid us to seek it because she seeks something else?
If we look for the essentially logical distinction between the two points of view above indicated, between that which seeks a knowledge of ultimate causes, and that which seeks complete and economical descriptions, we observe that it is in the existential judgment, which is present in the older point of view, while absent in the later one. It is evident, also, that the older point of view, therefore, is a metaphysical point of view. The great role which materialism played thirty and forty years ago was an inevitable result of the great triumphs of physical science, when physicists defined the goal of their science as metaphysical insight, insight into the eternal laws of the movements of matter of which all change in the world is the resulting effect.
It is no doubt more intelligent to recognize science as the effort to describe experience rather than to try to regard it as explaining experience in any ultimate sense. Yet many will feel that the older point of view had a more substantial purpose than the new one. It at least was seeking the Veritas which must exist. We might not like materialism, but the science of that faith was a courageous science not afraid of the truth wherever it might be found.
​He who feels this attitude longs for the existential judgment. His mood is not satisfied with science as now defined; description is not enough, and he demands the explanation of experience. The experience which is to be explained is the experience with some of whose aspects we became acquainted in the first section of this paper. It is experience characterized by the outer world and the fellow man as transcendent objects,—in a word, by the natural view of the world.
* ↑ Kr. der R. Erf.,' II., p. 342.
* ↑ *See Münsterberg, 'Aufgaben und Methoden der Psychologie,' p. 117.
* ↑ 'Logik,' Vol. II., 2te. Abtheilung, pp. 255, 257, 259.
* ↑ Philosophische Studien, Bd. X., Heft 1.
* ↑ 'Kr. der R. Erf.,' I., p. 202.
* ↑ 'Kr. der R. Erf.,' I., p. .3.
* ↑ 'Kr. der R. Erf.,' Vol. I., p. xiii; Vol. II., p. 492.
* ↑ The Science of Mechanics,' translated from 2d ed., Chicago, 1893, p, 490.
* ↑ 'Philosophie als Denken der Welt,' p. 43.
* ↑ 'Ueber die Stellung der Psychologic zur Philosophie,' Vierteljahrschrift für Wissenschaftliche Philosophie, I., p. 471.
* ↑ I owe this illustration to Professor Royce.
* ↑ 'Der Menschliche Weltbegriff,' p. 114.
* ↑ 'Kr. der R. Erf.,' II., p. 376.
* ↑ L. c. Compare Professor Dewey in the Journal of Philosophy. Psychology and Scientific Methods, Vol. II., No. 15. " Experience is always of thats; and the most comprehensive and inclusive experience of the universe which the philosopher himself can obtain is the experience of a characteristic that."
* ↑ William James in the Journal of Philosophy, Psychology and Scientific Methods, Vol. I., No. 18, 'Does Consciousness Exist.'
* ↑ Translation by Jones and Walley, p. 1.
* ↑ L. c., p. 2.
* ↑ Helmholtz, 'Ueber die Erhaltung der Kraft,' p. 2, Berlin, 1847.
* ↑ 'Ueber E. Mach's und H. Herz's Principielle AuflFassung der Physik,' by Kleinpeter in Archiv für Phil., II. Abtheilung, Bd. V., Heft. 2, p. 176.
* ↑ Vol. I., p. iii.
* ↑ P. 45.