ISO 



NATURE 



[Dec. 24, 1874 



be necessary to enable the reader to make out the truth 

 by considering the matter for himself. 



Among the scientific investigators who have especially 

 directed their efforts towards the purification of physical 

 science from all metaphysical infection and from all arbi- 

 trary hypotheses, and, on the contrary, have striven to 

 make it more and more a simple and faithful expres- 

 sion of the laws of the facts, Sir W. Thomson occupies 

 one of the first places, and he has consciously made pre- 

 cisely this his aim from the beginning of his scientific 

 career. This very thing seems to me to be one of the 

 chief services rendered by the present book, while in Mr. 

 Zollner's eyes it forms its fundamental defect. The latter 

 would like to see, instead of the "inductive" method of 

 the scientific investigator, a predominantly "deductive" 

 method introduced. We have all hitherto employed the 

 inductive process to discover new laws, or, as the case 

 may be, hypotheses ; the deductive to develop their conse- 

 quences for the purpose of their verification. I do not 

 find in Mr. Zollner's book a distinct declaration by which 

 his new mode of procedure may be distinguished from 

 that generally followed. Judging from what he aims at 

 as his ultimate object, it comes to the same thing as 

 Schopenhauer's JVIetaphysics. The stars are to love and 

 hate one another, feel pleasure and displeasure, and to 

 try to move in a way corresponding to these feelings. 

 Indeed, in blurred imitation of the principle of Least 

 Action (pp. 326, 327), Schopenhauer's Pessimism, which 

 declares this world to be indeed the best of possible 

 worlds, but worse than none at all, is formulated as an 

 ostensibly generally applicable principle of the smallest 

 amount of discomfort, and this is proclaimed as the 

 highest law of the world, living as well as lifeless. 



Now, that a man who mentally treads such paths 

 should recognise in the method of Thomson and Tait's 

 book the exact opposite of the right way, or of that which 

 he himself considers such, is natural ; that he should 

 seek the ground of the contradiction, not where it is 

 really to be found, but in all conceivable personal weak- 

 nesses of his opponents, is quite in keeping with the 

 intolerant manner in which the adherents of metaphysical 

 articles of faith are wont to treat their opponents, in order 

 to conceal from themselves and from the world the weak- 

 ness of their own position. Mr. ZoUner is convinced 

 "that the majority of the present representatives of the 

 exact sciences are wanting in a clearly conceived intelli- 

 gence of the first principles of the theory of perception" 

 (p. viii.) This he tries to confirm by reference to sup- 

 posed gross errors made by several of them. 



Here then, ol course, Messrs. Thomson and Tait must 

 submit to the ordeal. They have, in paragraphs 381-385 

 of the present book given expression to their conviction 

 as to the right use of scientific hypotheses. They, in 

 paragraph 385, find fault with hypotheses which are too 

 remote trom observable facts, and select, as instances of 

 their injurious influence, naturally only such as, by their 

 exiensive diffusion and by the authority of their origi- 

 nators, have been really influential. In this connection 

 they place side by side the law of electrical action at a 

 distance propounded by our countryman, VV. Weber, and 

 the emission theory of light as worked out by Newton. 

 This juxtaposition is the best proof that the English 

 authors had nothing in view that should wound a healthy 

 German national feeling. 



It has not as yet, I believe, come to such a pass in 

 Germany — it is to be hoped it never will — that hypotheses 

 may not be criticised, whatever be the eminence of their 

 propounders. Should it actually ever come to this, then 

 indeed Mr. ZoUner and his metaphysical friends would 

 be justified in bewailing, or it may be in triumphing over, 

 the destruction of German science. No one can be 

 blamed for having advanced a hypothesis which the 

 further progress of science shows to be inadmissible, just 

 as it is no discredit for one who has to seek his way in 



an entirely unknown country to take the wrong road for 

 once, in spite of his utmost attention and consideration. 

 It is further obvious that whoever regards as erroneous a 

 hypothesis which has captivated the minds of a large 

 number ol scientific men must necessarily hold that it, for 

 the time being, injures and retards the progress of science, 

 and will be justified in expressing this opinion, if it 

 becomes his duty to advise, according to his matured 

 conviction, a student as to the path he should follow. 



One of the arguments which Sir W. Thomson has 

 adduced to prove the inadmissibility of Weber's hypo- 

 thesis, is that it contradicts the law of the conservation 

 of energy. I was also obliged to bring forward the same 

 allegation somewhat later in a paper * published in the 

 year 1870. Now Mr. Zollner, relying on the authority of 

 Mr. C. Neumann, has assumed that this allegation is 

 erroneous. On the contrary, Weber's law seems to him 

 to be another universal law of all forces in nature (it is 

 not explained how these different universal laws agree 

 with one another), and he devotes twentypages of his intro- 

 duction to the purpose of airing his indignation at the 

 intellectual and moral dulness of those who attack it. 

 Mr. Zollner will, no doubt, since then, have become aware 

 that it is at least imprudent, without other support than 

 the authority of one of the parties in a scientific debate, 

 to try to help the other by libellous remarks, apart from 

 the consideration that by such means one can contribute 

 nothing to the settlement of the dispute, but perhaps 

 much to its embitterment. Mr. C. Neumann was himself 

 a party in this affair ; my objections applied also to the 

 theory of electrodynamic actions, to which he then ad- 

 hered. He has since then given up this theory. He and 

 also Mr. W. Weber thought that they could maintain the 

 original theory of the latter, if they took into considera- 

 tion the co-operative action of molecular forces in the 

 case of closely approximated electrical masses. I then, 

 in my second contribution to the theory of electrodyna- 

 niics,f pointed out that the assumption of molecular forces 

 does not stop the leak in Weber's theory. In the mean- 

 time Mr. C. Neumann himself, before he knew of my 

 second paper, had given up the attempt to found a theory 

 of electrodynamics upon Weber's law, and had tried to 

 devise a nev/ law for that purpose. 



And here, in reference to the emphatic way in which 

 our opponent speaks of the deductive method, I would 

 make the following remarks on this example : — According 

 to the view hitherto held by the best scientific investi- 

 gators, the deductive method was not only justified, but 

 indeed required, when the admissibility of a hypothesis 

 was to be tested. Every legitimate hypothesis is an 

 attempt to establish a new and more general law 

 which shall include under it more facts than those 

 hitherto observed. The testing of it consists in this, 

 that we seek to develop all the consequences which 

 flow from it, in particular those which can be com- 

 pared with observable facts. I should therefore imagine 

 the first duty of those who would support Weber's 

 hypothesis to be, among other things, to see whether 

 this hypothesis can explain the most general fact, that 

 electricity, when no electromotive forces act on it, re- 

 mains at rest in all electrical conductors, and is there- 

 fore capable of continuing in stable equilibrium. If 

 Weber's hypothesis implies the contrary of this, as I have 

 attempted to prove, then the next thing to be done would 

 be to look out for such a modification of it as would 

 render stable equilibrium possible in the largest as well as 

 in the smallest conductors. According to my view, this 

 would have been a right course, and the one required by 

 the deductive method, but not to call a halt when incon- 

 venient consequences appear, and excuse oneself with the 

 plea that the right differential equations for the motion of 



* " Ucber die Bewegungsgleichungen der Elektrlcitat fiir ruhende 

 leitende Korper." Jjorchardt, Joiirnnl fur Mathematik, Bd. 72, 75. 

 + Borchardt, y,mrnal fur Matlicmntik, Rd. 75. 



