Page:Catholic Encyclopedia, volume 5.djvu/484

 ENERGY

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ENERGY

(Schafer). This, however, is a long way from experi- mental proof that the conservation of energy hokls in all vital processes with such rigid accuracy that every faintest change in the motor or sensory nerve-cells of the brain must have been completely determined by a preceding physical stimulus. Whether this proposi- tion be true or not, there is not as yet even a remote approach to experimental proof of it (cf. Ladd).

The Law Considered. — Character and Range. — About the character and range of the law, and its bear- ing on sundry philosophical problems, there has been and still is much dispute. As a rule, however, the most eminent scientists, e. g. men like Clerk Maxwell and Lord Kelvin, are most cautious and guarded in their enunciation of the law. Be it noted that, when strictly stated, this proposition, " The sum of the kinetic and potential energies of a conservative system amid all changes remains constant", first applies only to an isolated or closed system. But such systems are hypothetical or ideal. As a matter of fact, no group of agents in the present universe is or can be thus isolated. Next, the proposition may be stated, as a legitimate generalization, only of inanimate bodies and material energies. The law affords no justification for the assertion that the only energies in any particular system, still less in the universe as a whole, are mate- rial energies. Clerk Maxwell himself explicitly re- minds us that " we cannot assert that all energy must be either potential or kinetic, though we may not be able to conceive of any other form". Again, many physicists insist that this concept of energy con- tained in the formula proves, when examined closely, to be vague and elusive. H. Poiiicare asks: "What exactly remains constant?" And he concludes a searching analysis with the statement that " of the principle nothing is left but an enunciation: There is something which remains constant" (Science and Hy- pothesis, p. 127). As eminent a physicist as George F. Fitzgerald tells us that " the doctrine of the conser- vation of energy is most valuable, but it only goes a very little way in explaining phenomena" (Scientific Writings, p. 391). Helmholtz's extension of the prin- ciple in the statement, that " the total quantity of all the forces capable of work in the whole universe re- mains eternal and unchanged throughout all their changes", is a hazardous leap from positive science into very speculative metaphysics. This should be recognized. For even supposing the proposition true, it cannot be demonstrated a priori. It is not self- evident. It is obviously beyond the possibility of experimental proof. It assumes the present universe to be a closed system into which new agents or beings capable of adding to its energy have never entered. Lucien Poincar^'s contention is just: "It behooves us not to receive without a certain distrust the extension by certain philosophers to the whole Universe of a property demonstrated for those restricted systems which observation can alone reach. We know noth- ing of the Universe as a whole and every generalization of this kind outruns in singular fashion the limit of experiment." James Ward's account of its character is much the same: "Methodologically, in other woriis as a formal and regulative principle, it means much, really it means very little." It furnishes very little information about the past, present, or future of the universe.

Proof of the Law. — On what evidence precisely, then, does the principle rest? Here again we find con- siderable disagreement. E. Mach tells us: "Many deduce the principle from the impossibility of per- petual motion, which again they either derive from experience or deem self-evident. . . Others frankly claim only an experimental foundation for the princi- ple." He himself considers the justification of the law to be in part experimental, in part a logical or formal postulate of the intellect. We have already alluded to the view that it is implicit in Newton's laws

of motion. The principle of causality, according to others, is its parent, flayer himself quotes ex nihilo nil fit, and argues that creation or annihilation of a force lies beyond human power. Even Joule, who laboured so diligently to establish an experimental proof, would reinforce the latter with the proposition, that "it is manifestly absurd to suppose that the powers with which God has endowed matter can be destroyed". Preston judiciously observes: "The general principle of the conservation oi energy is not to be proved by mathematical formulie. A law of nature must be founded on experiment and observa- tion, and the general agreement of the law with facts leads to a general belief in its probable truth. Fur- ther, the conservation of energy cannot be absolutely proved even by experiment, for the proof of a law requires a universal experience. On the other hand, the law cannot be said to be untrue, even though it may seem to be contradicted by certain experiments, for in these cases energy may be dissipated in modes of which we are as yet unaware " ( p. 90). In view of the extravagant conclusions some writers have attempted to deduce from the doctrine, it is useful to note these serious divergencies of opinion as to what is its true justification among those who have a real claim to speak with authority on the subject.

We shall best approximate to the truth by distin- guishing three different parts of the doctrine of energy: the law of constancy; the law of transformation; and the law of dissipation or degradation. The law of transformation, that all known forms of material energy may be transmuted into each other, and are reconvertible, is a general fact which can only be ascer- tained and proved by experience. There is no a priori reason requiring it. The law of dissipation, that, as a matter of fact, in the course of the changes which take place in the present universe there is a constant ten- dency for portions of energy to become unusable, owing to the equal diffusion of heat through all parts of the system — this truth similarly seems to us to rest entirely on experience. Finally, with respect to the principle of quantitative constancy, the main proof must be experience — but experience in a broad sense. It has been shown by positive experiments with por- tions of inanimate matter that the more perfectly we can isolate a group of material agents from external interference, and the more accurately we can calculate the total quantity of energy possessed by the system at the beginning and end of a series of qualitative changes, the more perfectly our results agree. Fur- ther, modern physics constantly assumes this principle in most complex and elaborate calculations, and the agreement of its deductions with observed results veri- fies the assumption in a manner which would seem to be impossible were the principle not true. In fact, we may say that the assvunption of the truth of the law, when correctly formulated, lies now at the basis of all modern physical and chemical theories, just as the assumption of inertia or the constancy of mass is fun- damental to mechanics. At the same time we must not forget the hypothetical character of the conditions postulated, and the limitations in its application to particular concrete problems. Bearing tnis in mind, even if there occurs some novel experience, as, e. g., the fact that radium seemed capable of sustaining it- self at a higher temperature than surroimding objects and of emitting a constant supply of heat without any observable diminution of its own store of energy, science does not therefore immediately abandon its fundamental principle. Instead, it rightly seeks for some hypothesis by which this apparently rebellious fact can be reconciled with so widely ranging a general law — as, for example, the hypothesis that this eccen- tric substance possesses a peculiar power of constantly collecting energy from the neighbouring ether and then dispensing it in the form of heat; or, that the high complexity of the molecular constitution of