LIMITS OF OUR KNOWLEDGE OF NATURE, 17 



THE LIMITS OF OUR KXOWLEDGE OF JN^ATURE. 



Bt Pbofessor EMTL DU BOIS-EEYMOND,i 

 of the university of berlin. 



TRANSLATED FEOM THE GEEMAX, BY J. FITZGEEALD, A. M. 



JUST as a world-conqueror of ancient times, as he halts for a day 

 in the midst of his victorious career, might long to see the boun- 

 daries of the vast territories he has subjugated more clearly defined, 

 so that here he may levy tribute of some nation hitherto exempt, or 

 that there he may discern some natural barrier that cannot be over- 

 come by his horsemen, and which constitutes the true limit of his 

 power, in like manner it will not be out of place, if Natural Science, 

 the world-conqueror of our times, resting as on a festive occasion 

 from her labor, should strive to define the true boundaries of her im- 

 mense domain. And this undertaking I hold to be all the more legiti- 

 mate, because I believe there exist two widely-diflTused errors with re- 

 gard to the limits of natural science, and because I think it possible 

 that from the study of such a question, despite its apparent triviality, 

 some advantage might be derived even by those who do not at all 

 share in the errors of which I sjoeak. 



Hence I propose to investigate the limits of natural science ; and 

 first I must say what natural science is. 



Natural science — or, more definitely, knowledge of the physical 

 world with the aid of and in the sense of theoretical natural science 

 — means the reduction of all change, in the physical world to move- 

 ments of atoms produced independently of time by their central 

 forces ; or, in other words, natural science is the resolution of natural 

 processes into the mechanics of atoms. It is a fact of psychological 

 experience that, where such a resolution is practicable, our desire of 

 tracing things back to their causes is provisionally satisfied. The 

 propositions of mechanics are mathematically presentable, and have in 

 themselves the same apodictic certainty as the propositions of mathe- 

 matics. As the changes of the physical world are reduced to a con- 

 sent sum of potential and kinetic energy, which is inseparable from a 

 constant quantity of matter, there remains in these changes themselves 

 nothing further that needs explanation. 



What Kant says in the introduction to his " Metaphysical Elements 

 of Natural Science," viz., that " in each special natural science the 

 amount of science, properly so called, is equal to the amount of mathe- 

 matics it contains " — must, therefore, be further narrowed down, and 

 instead of mathematics we must read atomic mechanics. Plainly this 



^ An Address delivered at the Forty-fifth Congress of German Naturalists and Phy- 

 sicians at Leipsie. 



VOL. V. — 2 



