196 POPULAR SCIENCE MONTHLY 



mechanics should he the first model of mathematical physics; but since 

 then this science has developed; it is still developing, even rapidly 

 developing. And it is already necessary to modify in certain points 

 the scheme I outlined in 1900 and from which I drew two chapters of 

 ' Science and Hypothesis.' In an address at the St. Louis exposition 

 in 1904, I sought to survey the road traveled; the result of this in- 

 vestigation the reader shall see farther on. 



The progress of science has seemed to imperil the best established 

 principles, those even which were regarded as fundamental. Yet noth- 

 ing shows they will not be saved; and if this comes about only im- 

 perfectly, they will still subsist even though they are modified. The 

 advance of science is not comparable to the changes of a city, where 

 old edifices are pitilessly torn down to give place to new, but to the 

 continuous evolution of zoologic types which develop ceaselessly and 

 end by becoming unrecognizable to the common sight, but where an 

 expert eye finds always traces of the prior work of the centuries past. 

 One must not think then that the old-fashioned theories have been 

 sterile and vain. 



Were we to stop there, we should find in these pages some reasons 

 for confidence in the value of science, but many more for distrusting 

 it; an impression of doubt would remain; it is needful now to set 

 things to rights. 



Some people have exaggerated the role of convention in science; 

 they have even gone so far as to say that law, that scientific fact itself, 

 was created by the scientist. This is going much too far in the direc- 

 tion of nominalism. No, scientific laws are not artificial creations; we 

 have no reason to regard them as accidental, though it be impossible 

 to prove they are not. 



Does the harmony the human intelligence thinks it discovers in 

 nature exist outside of this intelligence? No, beyond doubt, a reality 

 completely independent of the mind which conceives it, sees or feels it, 

 is an impossibility. A world as exterior as that, even' if it existed, 

 would for us be forever inaccessible. But what we call objective 

 reality is, in the last analysis, what is common to many thinking beings, 

 and could be common to all; this common part, we shall see, can only 

 be the harmony expressed by mathematical laws. It is this harmony 

 then which is the sole objective reality, the only truth we can attain ; 

 and when I add that the universal harmony of the world is the source 

 of all beauty, it will be understood what price we should attach to the 

 slow and difficult progress which little by little enables us to know 

 it better. 



