September 19, 1913] 



SCIENCE 



383 



simpler constituents, yet the conservation of mass 

 seemed to lie at the very foundation of creation. 

 But nowadays the student finds little to disturb 

 him, perhaps too little, in the idea that mass 

 changes with velocity; and he does not always 

 realize the full meaning of the consequences which 

 are involved. 



This readiness to accept and incorporate 

 new facts into the scheme of physics may 

 have led to perhaps an undue amount of 

 scientific scepticism, in order to right the 

 balance. 



But a still deeper variety of comprehen- 

 sive scepticism exists, and it is argued that 

 all our laws of nature, so laboriously ascer- 

 tained and carefully formulated, are but 

 conventions after all, not truths: that we 

 have no faculty for ascertaining real truth, 

 that our intelligence was not evolved for 

 any such academic purpose ; that all we can 

 do is to express things in a form convenient 

 for present purposes and employ that mode 

 of expression as a tentative and pragmat- 

 ically useful explanation. 



Even explanation, however, has been dis- 

 carded as too ambitious by some men of 

 science, who claim only the power to de- 

 scribe. They not only emphasize the how 

 rather than the why — as is in some sort in- 

 evitable, since explanations are never ulti- 

 mate — but are satisfied with very abstract 

 propositions, and regard mathematical 

 equations as preferable to, because safer 

 than, mechanical analogies or models. 



To use an acute and familiar expression of 

 Gustav Kirchhoff, it is the object of science to 

 describe natural phenomena, not to explain them. 

 When we have expressed by an equation the cor- 

 rect relationship between different natural phe- 

 nomena we have gone as far as we safely can, and 

 if we go beyond we are entering on purely specu- 

 lative ground. 



But the modes of statement preferred 

 by those who distrust our power of going 

 correctly into detail are far from satisfac- 

 tory. Professor Schuster describes and 

 comments on them thus: 



Vagueness, which used to be recognized as our 

 great enemy, is now being enshrined as an idol to 

 be worshipped. We may never know what con- 

 stitutes atoms, or what is the real structure of the 

 ether; why trouble, therefore, it is said, to find 

 out more about them. Is it not safer, on the con- 

 trary, to confine ourselves to a general talk on 

 entropy, luminiferous vectors and undefined sym- 

 bols expressing vaguely certain physical relation- 

 ships? What really lies at the bottom of the great 

 fascination which these new doctrines exert on the 

 present generation is sheer cowardice; the fear of 

 having its errors brought home to it. . . . 



I believe this doctrine to be fatal to a healthy 

 development of science. Granting the impossi- 

 bility of penetrating beyond the most superficial 

 layers of observed phenomena, I would put the 

 distinction between the two attitudes of mind in 

 this way: One glorifies our ignorance, while the 

 other accepts it as a regrettable necessity. 



In further illustration of the modern 

 sceptical attitude, I quote from Poincare: 



Principles are conventions and definitions in 

 disguise. They are, however, deduced from experi- 

 mental laws, and these laws have, so to speak, been 

 erected into principles to which our mind attrib- 

 utes an absolute value. . . .. 



The fundamental propositions of geometry, for 

 instance Euclid's postulate, are only conventions; 

 and it is quite as unreasonable to ask if they are 

 true or false as to ask if the metric system is 

 true or false. Only, these conventions are con- 

 venient. . . . 



Whether the ether exists or not matters little — 

 let us leave that to the metaphysicians; what is 

 essential for us is that everything happens as if 

 it existed, and that this hypothesis is found to be 

 suitable for the explanation of phenomena. After 

 all, have we any other reason for believing in the 

 existence of material objects? That, too, is only 

 a convenient hypothesis. 



As an antidote against over-pressing 

 these utterances I quote from Sir J. Lar- 

 mor's preface: 



There has been of late a growing trend of 

 opinion, prompted in part by general philosophical 

 views, in the direction that the theoretical con- 

 structions of physical science are largely facti- 

 tious, that instead of presenting a valid image of 

 the relations of things on which further progress 

 can be based, they are still little better than a 

 mirage. . . . 



