Landmarks of Scientific Socialism: "Anti-Duehring"

by Friedrich Engels

Before the time of Herr Duehring materialists were wont to speak of matter and motion. He reduces motion to mechanical force as its necessary original form and so renders incomprehensible the real connection between matter and motion which was also not evident to the earlier materialists. Yet the thing is easy enough. Matter has never existed without motion, neither can it. Motion in space, the mechanical motion of smaller particles to single worlds, the motion of molecules as in the case of heat, or as electric or magnetic currents, chemical analysis or synthesis, organic life, each single atom of the matter of the world—they all discover themselves in one or other of the forms of motion or in several of them together at any given moment. All quiescence, all rest, is only significant in relation to this or that given form of motion. A body for example may be upon the ground in mechanical quiescence, in mechanical rest. This does not prevent its participation in the movements of the earth and of the whole solar system, just as little does it prevent its smallest component parts from completing the movements conditioned by the temperature or its atoms from going through a chemical process. Matter without motion is just as unthinkable as motion without matter. Motion is just as uncreatable or indestructible as matter itself, the older philosophy of Descartes proclaimed precisely that the quantity of motion in the world has been fixed from the beginning. Motion cannot be generated therefore it can only be transferred. If motion is transferred from one body to another, one may as far as it is regarded as transferring itself, as active, consider it as the original cause of motion, but so far as it is transferred, as passive. This active motion we call force; the passive, expression of force. It is therefore just as clear as noon that force is just as great as its expression because the same motion fulfils itself in both.

A motionless condition of matter is therefore one of the hollowest and most absurd notions, a mere delirium. In order to arrive at it one is obliged to consider the relative absence of motion in the case of a body lying on the ground, as absolute rest, and then to transfer this idea to the entire universe. This is made easier by the reduction of motion in general to mere mechanical force. By the limitation of motion to mere mechanical force we can conceive of a force as at rest, as confined, as momentarily ineffective. If for example in the transference of motion which transference is very frequently a somewhat complicated process in the carrying out of which various intermediate steps are necessary, one may stay the actual transference at a chosen point and stop the process, as for example if one loads a gun and delays the moment when the charge shall be set at liberty by the pull of the trigger, through the firing of powder. Therefore one may conceive of matter as being loaded with force in the unprogressive static period, and this Herr Duehring appears to mean by his unity of matter and force if indeed he means anything at all. This notion is absurd, since it pictures as absolute for the entire universe a condition which is by nature only relative and to which therefore only a portion of matter can be subjected at one and the same time. Let us look at it from this point of view and we do not escape the difficulty of explaining first how the universe came to be loaded and in the second place, whose finger drew the trigger. We may revolve all we please but under the guidance of Herr Duehring we always come back over and over again to the finger of God.

From astronomy our realist philosopher passes on to mechanics and physics and complains that the mechanical theory of heat has brought us no further in the course of a generation than the point which Robert Mayer reached by his own efforts. Moreover the whole thing is very obscure. We must "always remember that with conditions of the movement of matter statical conditions are also given and that these last are not measured in mechanical work. If we have earlier typified nature as a great workwoman, and we still hold to the statement, we must now add that the static condition, the condition of rest, does not imply any mechanical labor. We are again without the bridge from the static to the dynamic and if latent heat, so called, is up to the present a stumbling block to the theory we can recognise a lack which may be denied in the cosmic process."

This whole oracular utterance is again merely an outpouring of bad science which very clearly perceives that it has got itself into a place from which it cannot be saved by creating motion from a state of absolute freedom from motion, and is ashamed to call upon its only saviour, the Creator of heaven and earth. If in mechanics, heat included, there is no bridge to be found from statics to dynamics, from equipoise to motion, why should Herr Duehring be obliged to find a bridge from his condition of absence of motion to motion? Thus he would have the luck to escape from his dilemma.

In ordinary mechanics the bridge from statics to dynamics is—the push from the outside. If a stone of the weight of a hundred grammes be lifted ten meters high and then flung free so that it should remain hanging in a self-contained condition and in a state of rest, you would have to appeal to a public of sucking infants to declare that the existing condition of that body represents no mechanical labor and that its removal from its earlier condition has no measure in mechanical work. Any passerby would tell Herr Duehring that the stone did not come on the string by its own efforts and the first good hand book in mechanics would inform him that if he let the stone fall again, the latter in its fall does just as much mechanical work as is necessary to lift it to the height of ten meters. The very simple fact that the stone is suspended represents mechanical force in itself, since if it remain long enough, the string breaks, as soon as it, as a result of its chemical constitution, is no longer strong enough to hold the stone. All mechanical phenomena, may, we must inform Herr Duehring, be reduced to just such simple fundamental forms, and the engineer is still unborn who cannot discover the bridge from statics to dynamics as long as he has sufficient initial force at his disposal.

It is quite a hard nut and bitter pill for our metaphysician that motion should find its measure in its opposite rest. It is such a glaring contradiction, and every contradiction is an absurdity in the eyes of Herr Duehring. It is nevertheless true that the hanging stone by reason of its weight and its distance from the ground represents a means of mechanical movement sufficiently easily measured in different ways, as for example through gravity direct, through glancing on an incline or through the undulation of a wave—and it is just the same with a loaded gun. The expression of motion in terms of its opposite rest presents no difficulty at all to the dialectic philosophy. The whole contradiction in its eyes is merely relative, for absolute rest, complete equipose does not exist. The movement of the particles strives towards equipose, the movement of the mass in turn destroys the equipose, so that rest and equipose where they occur are the results of arrested motion, and it is evident that this motion is capable of being measured in respect of its results, of being expressed in itself and of being restored in some form or other external to itself. But Herr Duehring would never be satisfied with such a simple explanation of the matter. Like a good metaphysician he creates a yawning gulf between motion and equipose which does not really exist and then wonders if he can find no bridge across the self-created chasm. He might just as well bestride his metaphysical Rosinante and hunt the "Ding an Sich" of Kant since it is in the last analysis nothing else than this which stands behind the undiscoverable bridge.

But what about the mechanical theory of heat and of latent heat which is a "stumbling block" in the path of the theory?

If one convert a pound of ice at freezing point under normal atmospheric pressure into a pound of water of the same temperature by means of heat there vanishes a quantity of heat which could heat the same pound of water from 0° centigrade to 79° centigrade, or seventy-nine pounds of water one degree centigrade. If one heat this pound of water to boiling point, that is, to one hundred degrees centigrade and change it into steam of the heat of one hundred degrees centigrade there vanishes up to the time when the last of the water is changed into steam a seven fold greater quantity of heat, capable of raising the temperature of 537.2 pounds of water one degree. This dissipated heat is called latent. It is transformed, by cooling the steam, into water again, and the water into ice, so the same mass of heat which was formerly latent, is again set free, that is, as heat capable of being felt and measured. This setting free of heat by the condensation of steam and the freezing of water is the reason that steam if it is cooled off at 100° transforms itself little by little into water, and that a mass of water at freezing point is but slowly transformed into ice. These are the facts. The question is what becomes of the heat while it is latent?

The mechanical theory of heat according to which the heat of a body at a certain temperature is dependent upon the greater or less vibration of the smallest physical parts (molecules) a vibration which can, under certain conditions, be transformed into some other form of motion, shows the whole thing completely, that the latent heat has performed work, has been expended in work. By the melting of the ice the close connection of the separate particles is broken asunder and changed into a loose relationship; by the conversion of water into steam at boiling point a condition is entered where the separate molecules exercise no noticeable influence upon each other, and under the influence of heat fly from one another in all directions. It is now evident that the separate molecules of a body in the gaseous state are endowed with much greater energy than in the fluid state, and in the fluid state than in the solid. Latent heat is therefore not dissipated, it is merely transformed and has taken on the form of molecular elasticity.

As soon as conditions are at an end under which the molecules can exercise this relative freedom with regard to each other as soon namely as the temperature falls below one hundred degrees to zero, this elasticity becomes released and the molecules come together with the same force with which they formerly flew apart, but only to appear again as heat, as exactly the same quantity of heat as was latent before. This explanation is of course a hypothesis, as is the whole mechanical theory of heat, in so far as no one has yet seen a molecule, much less a molecule in motion. Like all recent theories, this hypothesis is full of flaws but it can at least offer an explanation which does not conflict with the uncreatability and indestructibility of motion and it is able to give an account of the whereabouts of the heat in the transformation. Latent heat is therefore by no means an obstacle in the way of the mechanical theory of heat. On the contrary this theory for the first time provides a rational explanation of the subject and an obstacle arises from the fact in particular that the physicists make use of the old and ineffective expression "latent heat" to signify the heat transformed into some other shape by molecular energy.