1 March 1920, Stuttgart
My dear friends,
The present course of lectures will constitute a kind of continuation of the one given when I was last here. I will begin with those chapters of physics which are of especial importance for laying a satisfactory foundation for a scientific world view, namely the observations of heat relations in the world. Today I will try to lay out for you a kind of introduction to show the extent to which we can create a body of meaningful views of a physical sort within a general world view. This will show further how a foundation may be secured for a pedagogical impulse applicable to the teaching of science. Today we will therefore go as far as we can towards outlining a general introduction.
The theory of heat, so-called, has taken a form during the 19th century which has given a great deal of support to a materialistic view of the world. It has done so because in heat relationships it is very easy to turn one's glance away from the real nature of heat, from its being, and to direct it to the mechanical phenomena arising from heat.
Heat is first known through sensations of cold, warmth, lukewarm, etc. But man soon learns that there appears to be something vague about these sensations, something subjective. A simple experiment which can be made by anyone shows this fact.
Imagine you have a vessel filled with water of a definite temperature, \(t\); on the right of it you have another vessel filled with water of a temperature \(t-t_1\), that is of a temperature distinctly lower than the temperature in the first vessel. In addition, you have a vessel filled with water at a temperature \(t+t_1\). When now, you hold your fingers in the two outer vessels you will note by your sensations the heat conditions in these vessels. You can then plunge your fingers which have been in the outer vessels into the central vessel and you will see that to the finger which has been in the cold water the water in the central vessel will feel warm, while to the finger which has been in the warm water, the water in the central vessel will feel cold. The same temperature therefore is experienced differently according to the temperature to which one has previously been exposed. Everyone knows that when he goes into a cellar, it may feel different in winter from the way it feels in summer. Even though the thermometer stands at the same point circumstances may be such that the cellar feels warm in the winter and cool in the summer. Indeed, the subjective experience of heat is not uniform and it is necessary to set an objective standard by which to measure the heat condition of any object or location. Now, I need not here go into the elementary phenomena or take up the elementary instruments for measuring heat. It must be assumed that you are acquainted with them. I will simply say that when the temperature condition is measured with a thermometer, there is a feeling that since we measure the degree above or below zero, we are getting an objective temperature measurement. In our thinking we consider that there is a fundamental difference between this objective determination in which we have no part and the subjective determination, where our own organization enters into the experience.
For all that the 19th century has striven to attain it may be said that this view on the matter was, from a certain point of view, fruitful and justified by its results. Now, however, we are in a time when people must pay attention to certain other things if they are to advance their way of thinking and their way of life. From science itself must come certain questions simply overlooked in such conclusions as those I have given. One question is this: Is there a difference, a real objective difference, between the determination of temperature by my organism and by a thermometer, or do I deceive myself for the sake of getting useful practical results when I bring such a difference into my ideas and concepts? This whole course will be designed to show why today such questions must be asked. From the principal questions it will be my object to proceed to those important considerations which have been overlooked owing to exclusive attention to the practical life. How they have been lost for us on account of the attention to technology you will see. I would like to impress you with the fact that we have completely lost our feeling for the real being of heat under the influence of certain ideas to be described presently. And, along with this loss, has gone the possibility of bringing this being of heat into relation with the human organism itself, a relation which must be all means be established in certain aspects of our life. To indicate to you in a merely preliminary way the bearing of these things on the human organism, I may call your attention to the fact that in many cases we are obliged today to measure the temperature of this organism, as for instance, when it is in a feverish condition. This will show you that the relation of the unknown being of heat to the human organism has considerable importance. Those extreme conditions as met with in chemical and technical processes will be dealt with subsequently. A proper attitude toward the relation of the unknown being of heat to the human organism has considerable importance. Those extreme conditions as met with in chemical and technical processes will be dealt with subsequently. A proper attitude toward the relation of the heat-being to the human organism cannot, however, be attained on the basis of a mechanical view of heat. The reason is, that in so doing, one neglects the fact that the various organs are quite different in their sensitiveness to this heat-being, that the heart, the liver, the lungs differ greatly in their capacity to react to the being of heat. Through the purely physical view of heat no foundation is laid for the real study of certain symptoms of disease, since the varying capacity to react to heat of the several organs of the body escapes attention. Today we are in no position to apply to the organic world the physical views built up in the course of the 19th century on the nature of heat. This is obvious to anyone who has an eye to see the harm done by modern physical research, so-called, in dealing with what might be designated the higher branches of knowledge of the living being. Certain questions must be asked, questions that call above everything for clear, lucid ideas. In the so-called “exact science,” nothing has done more harm than the introduction of confused ideas.
What then does it really mean when I say, if I put my fingers in the right and left hand vessels and then into a vessel with a liquid of an intermediate temperature, I get different sensations? Is there really something in the conceptual realm that is different from the so-called objective determination with the thermometer? Consider now, suppose you put thermometers in these two vessels in place of your fingers. You will then get different readings depending on whether you observe the thermometer in the one vessel or the other. If then you place the two thermometers instead of your fingers into the middle vessel, the mercury will act differently on the two. In the one it will rise; in the other it will fall. You see the thermometer does not behave differently from your sensations. For the setting up of a view of the phenomenon, there is no distinction between the two thermometers and the sensation from your finger. In both cases exactly the same thing occurs, namely a difference is shown from the immediately preceding conditions. And the thing our sensation depends on is that we do not within ourselves have any zero or reference point. If we had such a reference point then we would establish not merely the immediate sensation but would have apparatus to relate the temperature subjectively perceived, to such a reference point. We would then attach to the phenomenon just as we do with the thermometers something which really is not inherent in it, namely the variation from the reference point. You see, for the construction of our concept of the process there is no difference.
It is such questions as these that must be raised today if we are to clarify our ideas, or all the present ideas on these things are really confused. Do not imagine for a moment that this is of no consequence. Our whole life process is bound up with this fact that we have in us no temperature reference point. If we could establish such a reference point within ourselves, it would necessitate an entirely different state of consciousness, a different soul life. It is precisely because the reference point is hidden for us that we lead the kind of life we do.
You see, many things in life, in human life and in the animal organism, too, depend on the fact that we do not perceive certain processes. Think what you would have to do if you were obliged to experience subjectively everything that goes on in your organism. Suppose you had to be aware of all the details of the digestive process. A great deal pertaining to our condition of life rests on this fact that we do not bring into our consciousness certain things that take place in our organism. Among these things is that we do not carry within us a temperature reference point — we are not thermometers. A subjective-objective distinction such as is usually made is not therefore adequate for a comprehensive grasp of the physical.
It is this which has been the uncertain point in human thinking since the time of ancient Greeks. It had to be so, but it cannot remain so in the future. For the old Grecian philosophers, Zeno in particular, had already orientated human thinking about certain processes in a manner strikingly opposed to outer reality. I must call your attention to these things even at the risk of seeming pedantic. Let me recall to you the problem of Achilles and the tortoise, a problem I have often spoken about.
Let us assume we have the distance traveled by Achilles in a certain time \(a\). This represents the rate at which he can travel. And here we have the tortoise \(s\), who has a start on Achilles. Let us take the moment when Achilles gets to the point marked \(1\). The tortoise is ahead of him. Since the problem stated that Achilles has to cover every point covered by the tortoise, the tortoise will always be a little ahead and Achilles can never catch up. But, the way people would consider it is this. You would say, yes, I understand the problem all right, but Achilles would soon catch the tortoise. The whole thing is absurd. But if we reason that Achilles must cover the same path as the tortoise and the tortoise is ahead, he will never catch the tortoise. Although people would say this is absurd, nevertheless the conclusion is absolutely necessary and nothing can be urged against it. It is not foolish to come to this conclusion but on the other hand, it is remarkably clever considering only the logic of the matter. It is a necessary conclusion and cannot be avoided. Now what does all this depend on? It depends on this: that as long as you think, you cannot think otherwise than the premise requires. As a matter of fact, you do not depend on thinking strictly, but instead you look at the reality and you realize that it is obvious that Achilles will soon catch the tortoise. And in doing this you uproot thinking by means of reality and abandon the pure thought process. There is no point in admitting the premises and then saying, “Anyone who thinks this way is stupid.” Through thinking alone we can get nothing out of the proposition but that Achilles will never catch the tortoise. And why not? Because when we apply our thinking absolutely to reality, then our conclusions are not in accord with the facts. They cannot be. When we turn our rationalistic thought on reality it does not help us at all that we establish so-called truths which turn out not to be true. For we must conclude if Achilles follows the tortoise that he passes through each point that the tortoise passes through. Ideally this is so; in reality he does nothing of the kind. His stride is greater than that of the tortoise. He does not pass through each point of the path of the tortoise. We must, therefore, consider what Achilles really does, and not simply limit ourselves to mere thinking. Then we come to a different result. People do not bother their heads about these things but in reality they are extraordinarily important. Today especially, in our present scientific development, they are extremely important. For only when we understand that much of our thinking misses the phenomena of nature if we go from observation to so-called explanation, only in this case will we get the proper attitude toward these things.
The observable, however, is something which only needs to be described. That I can do the following for instance, calls simply for a description: here I have a ball which will pass through this opening. We will now warm the ball slightly. Now you see it does not go through. It will only go through when it has cooled sufficiently. As soon as I cool it by pouring this cold water on it, the ball goes through again. This is the observation, and it is this observation that I need only describe. Let us suppose, however, that I begin to theorize. I will do so in a sketchy way with the object merely of introducing the matter. Here is the ball; it consists of a certain number of small parts — molecules, atoms, if you like. This is not observation, but something added to observation in theory. At this moment, I have left the observed and in doing so I assume an extremely tragic role. Only those who are in a position to have insight into these things can realize this tragedy. For you see, if you investigate whether Achilles can catch the tortoise, you may indeed begin by thinking “Achilles must pass over every point covered by the tortoise and can never catch it.” This may be strictly demonstrated. Then you can make an experiment. You place the tortoise ahead and Achilles or some other who does not run even so fast as Achilles, in the rear. And at any time you can show that observation furnishes the opposite of what you conclude from reasoning. The tortoise is soon caught.
When, however, you theorize about the sphere, as to how its atoms and molecules are arranged, and when you abandon the possibility of observation, you cannot in such a case look into the matter and investigate it — you can only theorize. And in this realm you will do no better than you did when you applied your thinking to the course of Achilles. That is to say, you carry the whole incompleteness of your logic into your thinking about something which cannot be made the object of observation. This is the tragedy. We build explanation upon explanation while at the same time we abandon observation, and think we have explained things simply because we have erected hypotheses and theories. And the consequence of this course of forced reliance on our mere thinking is that this same thinking fails us the moment we are able to observe. It no longer agrees with the observation.
You will remember I already pointed out this distinction in the previous course when I indicated the boundary between kinematics and mechanics. Kinematics describes mere motion phenomena or phenomena as expressed by equations, but it is restricted to verifying the data of observation.
The moment we pass over from kinematics to mechanics where force and mass concepts are brought in, at this moment, we cannot rely on thinking alone, but we begin simply to read off what is given from observation of the phenomena. With unaided thought we are not able to deal adequately even with the simplest physical process where mass plays a role. All the 19th century theories, abandoned now to a greater or lesser extent, are of such a nature that in order to verify them it would be necessary to make experiments with atoms and molecules. The fact that they have been shown to have a practical application in limited fields makes no difference. The principle applies to the small as well as to the large. You remember how I have often in my lectures called attention to something which enters into our considerations now wearing a scientific aspect. I have often said: From what the physicists have theorized about heat relations and from related things they get certain notions about the sun. They describe what they call the “physical conditions” on the sun and make certain claims that the facts support the description. Now I have often told you, the physicists would be tremendously surprised if they could really take a trip to the sun and could see that none of their theorizing based on terrestrial conditions agreed with the realities as found on the sun. These things have a very practical value at the present, a value for the development of science in our time. Just recently news has gone forth to the world that after infinite pains the findings of certain English investigators in regard to the bending of starlight in cosmic space have been confirmed and could now be presented before a learned society in Berlin. It was rightly stated there “the investigations of Einstein and others on the theory of relativity have received a certain amount of confirmation. But final confirmation could be secured only when sufficient progress had been made to make spectrum analysis showing the behavior of the light at the time of an eclipse of the sun. Then it would be possible to see what the instruments available at present failed to determine.” This was the information given at the last meeting of the Berlin Physical Society. It is remarkably interesting. Naturally the next step is to seek a way really to investigate the light of the sun by spectrum analysis. The method is to be by means of instruments not available today. Then certain things already deduced from modern scientific ideas may simply be confirmed. As you know it is thus with many things which have come along from time to time and been later clarified by physical experiments. But, people will learn to recognize the fact that it is simply impossible for men to carry over to conditions on the sun or to the cosmic spaces what may be calculated from those heat phenomena available to observation in the terrestrial sphere. It will be understood that the sun's corona and similar phenomena have antecedents not included in the observations made under terrestrial conditions. Just as our speculations lead us astray when we abandon observation and theorize our way through a world of atoms and molecules, so we fall into error when we go out into the macrocosm and carry over to the sun what we have determined from observations under earth conditions. Such a method has led to the belief that the sun is a kind of glowing gas ball, but the sun is not a glowing ball of gas by any means. Consider a moment, you have matter here on the earth. All matter on the earth has a certain degree of intensity in its action. This may be measured in one way or another, be density or the like, in any way you wish, it has a definite intensity of action. This may become zero. In other words, we may have empty space. But the end is not yet. That empty space is not the ultimate condition I may illustrate to you by the following: Assume to yourselves that you had a boy and that you said, “He is a rattle-brained fellow. I have made over a small property to him but he has begun to squander it. He cannot have less than zero. He may finally have nothing, but I comfort myself with the thought that he cannot go any further once he gets to zero!” But you may now have a disillusionment. The fellow begins to get into debt. Then he does not stop at zero; the thing gets worse than zero. It has a very real meaning. As his father, you really have less if he gets into debt than if he stopped when he had nothing.
The same sort of thing, now, applies to the condition on the sun. It is not usually considered as empty space but the greatest possible rarefaction is thought of and a rarefied glowing gas is postulated. But what we must do is to go to a condition of emptiness and then go beyond this. It is in a condition of negative material intensity. In the spot where the sun is will be found a hole in space. There is less there than empty space. Therefore all the effects to be observed in the sun must be considered as attractive forces not as pressures of the like. The sun's corona, for instance, must not be thought of as it is considered by the modern physicist. It must be considered in such a way that we have the consciousness not of forces radiating outward as appearances would indicate, but of attractive force from the hole in space, from the negation of matter. Here our logic fails us. Our thinking is not valid here, for the receptive organ or the sense organ through which we perceive it is our entire body. Our whole body corresponds in this sensation to the eye in the case of light. There is no isolated organ, we respond with our whole body to the heat conditions. The fact that we may use our finger to perceive a heat condition, for instance, does not militate against this fact. The finger corresponds to a portion of the eye. While the eye therefore is an isolated organ and functions as such to objectify the world of light as color, this is not the case for heat. We are heat organs in our entirety. On this account, however, the external condition that gives rise to heat does not come to us in so isolated a form as does the condition which gives rise to light. Our eye is objectified within our organism. We cannot perceive heat in an analogous manner to light because we are one with the heat. Imagine that you could not see colors with your eye but only different degrees of brightness, and that the colors as such remained entirely subjective, were only feelings. You would never see colors; you would speak of light and dark, but the colors would evoke in you no response and it is thus with the perception of heat. Those differences which you perceive in the case of light on account of the fact that your eye is an isolated organ, such differences you do not perceive at all in the case of heat. They live in you. Thus when you speak of blue and red, these colors are considered as objective. When the analogous phenomenon is met in the case of heat, that which corresponds to the blue and the red is within you. It is you yourself. Therefore you do not define it. This requires us to adopt an entirely different method for the observation of the objective being of heat from the method we use of the objective being of light. Nothing had so great a misleading effect on the observers of the 19th century as this general tendency to unify things schematically. You find everywhere in physiologies a “sense physiology.” Just as though there were such a thing! As though there were something of which it could be said, in general, “it holds for the ear as for the eye, or even for the sense of feeling or for the sense of heat. It is an absurdity to speak of a sense physiology and to say that a sense perception is this or that. It is possible only to speak of the perception of the eye by itself, or the perception of the ear by itself and likewise of our entire organism as heat sense organ, etc. They are very different things. Only meaningless abstractions result from a general consideration of the senses. But you find everywhere the tendency towards such a generalizing of these things. Conclusions result that would be humorous were they not so harmful to our whole life. If someone says — Here is a boy, another boy has given him a thrashing. Also then it is asserted — Yesterday he was whipped by his teacher; his teacher gave him a thrashing. In both cases there is a thrashing given; there is no difference. Am I to conclude from this that the bad boy who dealt out today's whipping and the teacher who administered yesterday's are moved by the same inner motives? That would be an absurdity; it would be impossible. But now, the following experiment is carried out: it is known that when light rays are allowed to fall on a concave mirror, under proper conditions they become parallel. When these are picked up by another concave mirror distant form the first they are concentrated and focused so that an intensified light appears at the focus. The same experiment is made with so-called heat rays. Again it may be demonstrated that these too can be focused — a thermometer will show it — and there is a point of high heat intensity produced. Here we have the same process as in the case of the light; therefore heat and light are fundamentally the same sort of thing. The thrashing of yesterday and the one of today are the same sort of thing. If a person came to such a conclusion in practical life, he would be considered a fool. In science, however, as it is pursued today, he is no fool, but a highly respected individual.
It is on account of things like this that we should strive for clear and lucid concepts, and without these we will not progress. Without them physics cannot contribute to a general world view. In the realm of physics especially it is necessary to attain to these obvious ideas.
You know quite well from what was made clear to you, at least to a certain extent, in my last course, that in the case of the phenomena of light, Goethe brought some degree of order into the physics of that particular class of facts, but no recognition has been given to him.
In the field of heat the difficulties that confront us are especially great. This is because in the time since Goethe the whole physical consideration of heat has been plunged into a chaos of theoretical considerations. In the 19th century the mechanical theory of heat as it is called has resulted in error upon error. It has applied concepts verifiable only by observation to a realm not accessible to observation. Everyone who believes himself able to think, but who in reality may not be able to do so, can propose theories. Such a one is the following: a gas enclosed in a vessel consists of particles. These particles are not at rest but in a state of continuous motion. Since these particles are in continuous motion and are small and conceived of as separated by relatively great distance, they do not collide with each other often but only occasionally. When they do so they rebound. Their motion is changed by this mutual bombardment. Now when one sums up all the various slight impacts there comes about a pressure on the wall of the vessel and through this pressure one can measure how great the temperature is. It is then asserted, “the gas particles in the vessel are in a certain state of motion, bombarding each other. The whole mass is in rapid motion, the particles bombarding each other and striking the wall. This gives rise to heat.” They may move faster and faster, strike the wall harder. Then it may be asked, what is heat? It is motion of these small particles. It is quite certain that under the influence of the facts such ideas have been fruitful, but only superficially. The entire method of thinking rests on one foundation. A great deal of pride is taken in this so-called “mechanical theory of heat,” for it seems to explain many things. For instance, it explains how when I rub my finger over a surface the effort I put forth, the pressure or work, is transformed into heat. I can turn heat back into work, in the steam engine for instance, where I secure motion by means of heat. A very convenient working concept has been built up along these lines. It is said that when we observe these things objectively going on in space, they are mechanical processes. The locomotive and the cars all move forward etc. When now, through some sort of work, I produce heat, what has really happened is that the outer observable motion has been transformed into motion of the ultimate particles. This is a convenient theory. It can be said that everything in the world is dependent on motion and we have merely transformation of observable motion into motion not observable. This latter we perceive as heat. But heat is in reality nothing but the impact and collision of the little gas particles striking each other and the walls of the vessel. The change into heat is as though the people in this whole audience suddenly began to move and collided with each other and with the walls etc. This is the Clausius theory of what goes on in a gas-filled space. This is the theory that has resulted from applying the method of the Achilles proposition to something not accessible to observation. It is not noticed that the same impossible grounds are taken as in the reasoning about Achilles and the tortoise. It is simply not as it is thought to be. Within a gas-filled space things are quite otherwise than we imagine them to be when we carry over the observable into the realm of the unobservable. My purpose today is to present this idea to you in an introductory way. From this consideration you can see that the fundamental method of thinking originated during the 19th century, begins to fail. For a large part of the method rests on the principle of calculating from observed facts by means of the differential concept. When the observed conditions in a gas-filled space are set down as differentials in accordance with the idea that we are dealing with the movements of ultimate particles, then the belief follows that by integrating something real is evolved. What must be understood is this: when we go from ordinary reckoning methods to differential equations, it is not possible to integrate forthwith without losing all contact with reality. This false notion of the relation of the integral to the differential has led the physics of the 19th century into wrong ideas of reality. It must be made clear that in certain instances one can set up differentials but what is obtained as a differential cannot be thought of as integrable without leading us into the realm of the ideal as opposed to the real. The understanding of this is of great importance in our relation to nature.
For you see, when I carry out a certain transformation period, I say that work is performed, heat produced and from this heat, work can again be secured by reversal of this process. But the processes of the organic cannot be reversed immediately. I will subsequently show the extent to which this reversal applies to the inorganic in the realm of heat in particular. There are also great inorganic processes that are not reversible, such as the plant processes. We cannot imagine a reversal of the process that goes on in the plant from the formation of roots, through the flower and fruit formation. The process takes its course from the seed to the setting of the fruit. It cannot be turned backwards like an inorganic process. This fact does not enter into our calculations. Even when we remain in the inorganic, there are certain macrocosmic processes for which our reckoning is not valid. Suppose you were able to set down a formula for the growth of a plant. It would be very complicated, but assume that you have such a formula. Certain terms in it could never be made negative because to do so would be to disagree with reality. In the face of the great phenomena of the world I cannot reverse reality. This does not apply, however, to reckoning. If I have today an eclipse of the moon I can simply calculate how in time past in the period of Thales, for instance, there was an eclipse of the moon. That is, in calculation only I can reverse the process, but in reality the process is not reversible. We cannot pass from the present state of the earth to former states — to an eclipse of the moon at the time of Thales, for instance, simply by reversing the process in calculation. A calculation may be made forward or backward, but usually reality does not agree with the calculation. The latter passes over reality. It must be defined to what extent our concepts and calculations are only conceptual in their content. In spite of the fact that they are reversible, there are no reversible processes in reality. This is important since we will see that the whole theory of heat is built on questions of the following sort: to what extent within nature are heat processes reversible and to what extent are they irreversible?