Review of Correlation and Conservation of Forces [From North American Review 100.2 (April 1865): 619-622.] ¹²

The Correlation and Conservation of Forces: a Series of Expositions, by Prof. Grove, Prof. Helmholtz, Dr. Mayer, Dr. Faraday, Prof. Liebig, and Dr. Carpenter; with an Introduction and brief Biographical Notices of the chief Promoters of the New Views. By Edward L. Youmans, M. D. New York: D. Appleton &Co. 1865. 12mo. pp. xlii., 438.

The essays collected in this volume have already an established reputation as summary expositions of the most interesting and instructive results of modern physical researches; and Dr. Youmans has done a great service to the American public, in presenting it with selections so well chosen and in such compact and readable shape.

That Dr. Youmans has great skill in book-making appears both in the present volume and in his recently published class-book of Chemistry. In the latter he has incorporated modern ideas of physical science with an apparently distinct apprehension of their true range and value. But this is strangely at variance with the vague talk with which he introduces these essays. It is unfortunate that the impression this Introduction is calculated to make about the scope and character of the essays should be allowed to prepossess the mind of the reader.

Dr. Youmans speaks of the general subject of these essays as “a new philosophy” and as “the new doctrine of force.” But the emphatic part of the general doctrine is not about the nature of force

as an entity or a causal agency, but about the quantitative elements and relations in those general orders of succession in physical phenomena which are manifested in motions. The word “force” is used only for a convenience, and by most of the writers with the same careful limitation and separation from any substantive signification as in mathematical mechanics. Dr. Mayer says: —

“The exact sciences are concerned with phenomena and measurable quantities. The first cause of things is Deity, — a being ever inscrutable by the intellect of man; while ‘higher causes,’ ‘supersensuous forces,’ and the rest, with all their consequences, belong to the delusive middle region of naturalistic philosophy and mysticism.”

The other essayists hold similar views, and disconnect the objects of scientific inquiry from those of religious thought and feeling. But their editor, occupying that “delusive middle region of naturalistic philosophy” which Dr. Mayer describes, and without heeding his warning, speaks of the progress which these essays are designed to illustrate, as showing a tendency “ever from the material toward the abstract, the ideal, the spiritual.” He confounds the scientific distinction between concrete material objects and abstract formal relations, with the philosophical distinction between the material and the spiritual, and illustrates what he understands by materialism, by instancing the crude devices of ancient astronomy.

“At length,” he says, “the labors of astronomers, terminating with Newton, struck away these crude devices, and substituted the action of a universal immaterial force. The course of astronomic science has thus been on a large scale to withdraw attention from the material and sensible, and to fix it upon the invisible and supersensuous. It has shown that a pure principle forms the immaterial foundation of the universe. From the baldest materiality we rise at last to a truth of the spiritual world, of so exalted an order that it has been said ‘to connect the mind of man with the Spirit of God.’

“The tendency thus illustrated by astronomy is characteristic in a marked degree of all modern science. Scientific inquiries are becoming less and less questions of matter, and more and more questions of force; material ideas are giving place to dynamical ideas.”

The editor speaks throughout this essay as if he were publishing a new Gospel of Force, according to Grove, Helmholtz, Mayer, Faraday, and others, — a design which no one would more earnestly reprobate than these distinguished physicists. Nothing can be conceived more erroneous than presenting these remarkable essays as illustrations and proofs of Mr. Herbert Spencer’s dynamism. The editor may honestly admire Mr. Spencer’s vagaries, but it is difficult to conceive how any

one with the scientific attainments which Dr. Youmans’s books exhibit, can have undesignedly so misrepresented the character of the writings he has here collected.

Modern science uses the words “force” and “cause” always under protest, and not to express any substantive object of scientific research. The are used to avoid paraphrase, and to express in each particular case that part of a series of related phenomena which, for some scientific reason, is to be separately considered; and they generally comprise those antecedent conditions of any phenomenon which bring it into the most extensive rational connection with other and more general phenomena. Professor Grove says of causes: —

“The common error, if I am right in supposing it to be such, consists in the abstraction of cause, and in supposing in each case a general secondary cause, — a something which is not the first cause, but which, if we examine it carefully, must have all the attributes of a first cause, and an existence independent of and dominant over matter.”

Of forces he says: —

“Do we know more of the phenomenon, viewed without reference to other phenomena, by saying it is produced by force? Certainly not. All we know or see is the effect; we do not see force, — we see motion or moving matter.”

Scientific ideas of cause and force are the same as those of the Positive Philosophy, though they are not derived from this source; the Positive Philosophy being itself derived from a one-sided attention to the ideas of modern science.

Dr. Mayer uses “force” and “phenomenon,” not as antithetical, but as species and genus. He divides phenomena into two species, “forces” and “properties.” Properties are unchangeable phenomena; forces are convertible phenomena, but convertible according to unchangeable laws, through balanced and correlated processes. The “indestructibility of matter” and “the conservation of force” mean in science only that certain measurable properties of matter persist unchanged throughout all natural changes, and that forces or convertible phenomena are so related that no changes can affect the measures according to which these forces are mutually convertible. Both these doctrines are concerned with measurable phenomena, and have nothing to do with the vague “matter” and “force” of naturalistic philosophy. There is nothing of an a priori or philosophic character about them.

If there be anything which should be credited exclusively to empirical science it is the establishment of these doctrines, which have only a superficial resemblance to anything which speculative philosophy has ever excogitated. Nevertheless Dr. Youmans, who ought to have known better, claims for Mr. Herbert Spencer

“the honor of crowning this sublime inquiry by showing that the law of the conservation, or as he prefers to term it ‘the Persistence of Force,’ as it is the underlying principle of all being, is also the fundamental truth of all philosophy. With masterly analytic skill he has shown that this principle, of which the human mind has just become fully conscious, is itself the profoundest law of the human mind, the deepest foundation of consciousness. He has demonstrated that the law of the Persistence of Force, of which the most piercing intellects of past times had but partial and unsatisfying glimpses, and which the latest scientific research has disclosed as a great principle of nature, has a yet more transcendent character; is, in fact, an a priori truth of the highest order, — a truth which is necessarily involved in our mental organization, which is broader than any possible induction, and of higher validity than any other truth whatever.”

The extravagant absurdity of this claim is only surpassed by that of Mr. Spencer’s pretensions, who is quoted as follows: —

“We might, indeed, be certain, even in the absence of any such analysis as the foregoing, that there must exist some principle which, as being the basis of science, cannot be established by science. All reasoned out conclusions whatever must rest on some postulate. As before shown, we cannot go on, merging derivative truths in these wider and wider truths from which they are derived, without reaching at last a widest truth, which can be merged in no other or derived from no other. And whoever contemplates the relation in which it stands to the truths of science in general will see that this truth, transcending demonstration, is the Persistence of Force. . . . . Such, then, is the foundation of any possible system of positive knowledge. Deeper than demonstration, deeper even than definite cognition, deep as the very nature of mind, is the postulate at which we have arrived.”

Mr. Spencer’s “Persistence of Force” may be deeper than definite cognition, — indeed, we have found it so; but the law of the conservation of force is essentially comprehensible and definite. It is exclusively concerned with the phenomenal and the measurable; and though it has not yet been demonstrated with mathematical certainty as a universal law of nature, yet experiment has rendered its universality so probable that no reasonable doubt of it remains in the minds of physicists.

The introductory remarks of Professor Grove’s essay on “the Correlation of Physical Forces,” contain an excellent discussion of the scientific use of the words “cause” and “force,” and may serve to correct the false impressions which the reader will get from the editor’s Introduction.