Herbert Spencer to Faraday   4 May 1857¹

The eternity of Force and not of forces

Economist Office Strand | May 4h 1857

Dear Sir

Being much interested in the subject of your late lecture on the conservation of Force² I respectfully ask you to consider, if you can possibly spare time, the following remarks.

You have doubts whether the considerations you advance are metaphysical or physical, but as you state that “we know matter only by its forces” ³, you can I think have no doubt that the subject you discuss is purely metaphysical. It concerns the convictions of mind of which all the discoveries of the chemist and all the calculations of the mathematician are parts and consequently embraces them all[.] It does not concern any properties of matter which we learn by observation and by our senses, but something beyond all properties, viz the possible annihilation or eternal existence of matter. This is not a question of sense, of course it is not a question of physics, and therefore is metaphysical[.] As such I treat it[.]

You “agree with those who admit the conservation of force to be a principle in physics as large and as sure as that of the indestructibility of matter”⁴, but as you also say that we know matter only by its forces, you imply that these forces are indestructible and you argue against the common mode of expressing the law of gravity, that it admits a [“]creation of power to an enormous amount” and “an annihilation of force”⁵. The point to which I beg to call your attention is the difference, apparently a very slight one, between the annihilation of force and the annihilation of forces, but which is all important. We continually find forces, as electricity and magnetism, lost or merged in one more general force, and we may find gravity so merged and lost, and yet the idea of force may for ever remain as long as man is in existence and the conviction of its eternity become only the more overwhelming as we merge all separate forces by our successive discoveries investigations and generalizations into one force. The forces of matter, so called are in truth only names which we for the help of our memories and the progress of our investigations give to a number of certain similar phenomena[.] You do not require to be told that there is no thing, answering to the terms gravity electricity caloric, as there are things answering to the terms a pound weight of lead, a Leyden jar and a rod hot poker; and the terms gravity electricity caloric etc are merely general names for many similar or precisely identical phenomena[.] In banishing every one of these names from our vocabulary we should not annihilate the phenomena; and by the same rule, should we banish them from science, we should not lessen nor destroy one atom of the force whatever it may be which is the cause of them all.

“The strict science of modern times” as you say has [“]tended more and more to produce the conviction that force can neither be created nor destroyed”⁶. This may with propriety I think be said to be one of the latest results of all inquiry and to be an ultimate result in which the mind will rest[.] Every days experience will confirm it. At the same time it is in harmony with our earliest and latest convictions. Every action of our lives is based on an internal conviction - expressed in the proverbial saying - a burnt child dreads the fire, that the force whatever is be which burns one day will burn the next and for ever. Under certain circumstances the fire may not burn, then doubt of the accuracy of the conviction arises, observation sets to work explains the circumstances but confirms the inherent conviction that force is one day what it was the day before[.] In such cases as the return of day and night which has never been interrupted the conviction is never followed by doubt and we invariably believe and always act on the belief that the sun will rise to morrow as he has risen to day; or if we express the matter more scientifically, we all practically and forever believe that the force which gives us day and night will continue to exist and to operate. If we carry our researches back to the beginning and onward to the possible annihilation of the race of man, we learn that day and night have been from the beginning and we believe that they will be hereafter; or that the force which produces them was before man and will, though he come to an end be eternal. In truth Astronomy and geology carry back the theme before history or man gets hold of it and prove that the force (or forces as science yet says) which now sustains man on the earth and sustains the earth and all the stars in their places has been in operation for countless ages bringing the crust of the earth to its present condition and keeping in harmony and order a wonderful universe parts of which it is mans greatest merit to comprehend. The last results of philosophy are then on this point strictly in accordance with our instinctive convictions and physics and metaphysics agree in the conclusion that force is indestructible[.]

To this great and universal principle you find the usual expression of the law of gravity an exception. “It appears[”] you say to [“]ignore entirely the principle of the conservation of force and to be in opposition to it”⁷ - because according to the expression it varies inversely as the square of the distance. The whole difficulty as the whole problem rests entirely on the word distance and the only definition to be given of this word must be obtained from metaphysics[.] Mathematics can neither explain nor define it[.] What is distance according to the square of which gravity is said to vary inversely? It is no thing[.] In mathematics it is only a succession of invisible points without length brea[d]th or thickness[.] It is a mere relation and the law of gravity which is said to vary as the square of the distance, varies as the square of no thing a sorry kind of law to counteract our instinctive convictions and all the deductions of science.

Distance as a relation has a definite meaning and now in consequence of almost instance telegraphic communication through great distances an immense interest. To understand its signification is of equal importance. What it means; or the sources of our ideas of it, to state which is to define it - is motion. First dawning on the mind by the muscular sensations of the hand in conjunction with the eye not yet trained to complete vision, as it gropes over the fount whence the infant draws his nourishment - then extended and confirmed by free use of arms and legs, then by wandering or being carried across a continent, combined with inherited knowledge, that other men have traversed continents, and finally observing and ascertaining that he is carried by the globe itself through the vast regions of space; the notion or idea of distance is formed in man. It corresponds to motion. It is the portion of space - the whole of which extends beyond the reach of our telescopes which motion on the surface of the earth, and the motion of the earth round the sun including its motion with the sun have enabled man to compass and to measure. It is for is an idea or state of mind arising from our muscular contractions, and the perceptions of our senses, including those of our predecessors as well as our own. When mathematicians therefore speak of gravity varying inversely as the distance, they only mean inversely to an idea of ours, or to the motion which is its source. Motion too is the source of our idea of time which corresponds to total known motion and both are in space which includes them includes all things and all the relations of things[.]

But space itself is no thing and it is not manifested to us as a force though our idea of it borrowed from motion is inseparable from all things[.] Every thing comes with it the idea of space[.] Even the communication by electricity, which transmitted westward actually annihilates time, (ie. is made with greater velocity than the revolving motion of the earth) has its battery at one spot, and its needle and dial plate at the other, and includes the idea of space though not of distance[.] Traveling like electricity seems and may be wholly independent of time or its measure motion. Its vis inertia is perfect rest. It like space too, if we cannot say that it includes, it belongs to all things. There is no thing though there are imponderable forces without gravity; It pervades the universe. It is greater than our idea of time measured by motion, The motion of longest duration yet ascertained. It was before the beginning of our reckoning the idea of it is involved in all the researches of the geologist and is wherever our reckoning reaches. It has no relation to time though time has a relation to it, ie, the motion which measures time is not independent of gravity. The same reasoning applies to the other word distance which is only a definite portion of space measured by motion as time is the whole of space yet known to man by motion. Gravity on this explanation is wholly independent of our idea of distance, and though we may be profoundly ignorant of its mode of operation - the expression of the law which you object to may be only a phrase, of which there are many in existence used to conceal our ignorance[.]

To me there seems to be many other relations which exist independent of time or of the motion by which time is measured. The existence of Queen Elizabeth⁸ influences at the moment the hopes and fears and character of English Men[.] So the existence of Julius Ceasar⁹ [sic], the Roman Republic, the Assyrian empire have a present influence, or operate with a certain force over all living men, The ideas of Berkeley¹⁰ as well as those of Shakespeare, the ideas of Mr Faraday and those of Mr Macaulay¹¹ are at this moment present to minds in the United States in Australia and in the [word illegible] of London. Our present ideas of all things - even of time included depend in part on ideas of our ancestors[.] The force whatever it might be which called these ideas originally into being is observably still in existence & still operating. Old empires and great writers have passed away, but not their influence. They and we and all of us exist in time ie in conjunction with the motion of the heavenly bodies, but the present evidence of the influence of the Assyrian and of ideas generated in England, extending to America and Australia has no other relation to time[.] It has no dependence on distance. It operates across oceans and ages by means of little marks which have no resemblance to the idea[.] The force in its origin was mental the present influence is solely and entirely mental[.] The minds of successive generations and of generations living far apart are linked together by the perishable body or even by signs which the perishable body makes, the links pass away and the influence or the force remains[.] This is quite as wonderful as the instant operation of electricity in different places, or as the constant operation of gravity be the law or the expression of the law what it may. The relations of electricity to space and of mental influence to time, a portion of space and gravity operating at a distance - or in relation to a portion of space seem kindred phenomena. They all negative the assumption that force cannot operate at a distance, or independently of the motion which measures time, electricity does so operate through many leagues, the mind does so operate through many ages. What is called attraction with all the forces which operate at insensible distances may be placed in the same category. No motion similar to that which is the source of our idea of time accompanies the operation[.] Except as all nature is in ultimate analysis mysterious there is nothing mysterious in gravity operating independently of motion or of distance, and nothing in its operations but the very contrary to teach us the eternity of force[.]

Let me add with reference to the transformation or absorption of forces one into another as mans generalizations proceed that the common supposition that what are now called elements are to be eternal is a mistake. Take iron as yet I believe an undecompounded metal as an example; in this condition it is generally speaking a production of ash[.] It is continually abraded corroded destroyed and dispersed[.] The common supposition is that the iron is always to be in existence[.] But it is susceptible of many combinations and as corroded or abraded may form combinations unknown to us so that the force which even in iron may never be by one atom diminished or destroyed while the metal itself having taken the new form may cease to be. The extraordinary progress of arts in modern time enabling us to pass from place to place with a velocity unknown to our ancestors, and to communicate from place to place with a still more,- to them