434 SCIENCE PROGRESS. 



fection of all mechanical hypotheses will show itself 

 here again and will prevent the complete carrying out of 

 the idea. 



But even if the laws of natural phenomena may really 

 be reduced to the laws of the corresponding forms of 

 energy, what advantage do we gain therefrom ? First, the 

 very considerable one, that a science free from hypothesis 

 becomes possible. We seek no longer forces whose exist- 

 ence we cannot prove between atoms which we cannot 

 observe, but we judge a process by the kind and quantity 

 of the vanishing, and appearing energies. These we are 

 able to measure, and all that it is necessary to know may 

 be expressed in this manner. What an enormous general 

 advantage this is, will be clear to every one whose scientific 

 conscience has suffered under the continual amalgamation 

 of facts and hypothesis which the physics and chemistry of 

 to-day offer us as rational science. Energetics offers us a 

 means of fulfilling in its true sense the demand of Kirchhoff 

 so oft misunderstood, namely, the substitution of the de- 

 scription of phenomena for the so-called explanation of 

 nature. With this freedom from hypothesis appears a 

 methodical unity which, it may be unhesitatingly affirmed, 

 has up till now never been attained. I have already re- 

 ferred to the philosophical significance of this unity of 

 principle in the conception of natural phenomena ; although 

 obvious from the very nature of the case, I may still call 

 attention in particular to the enormous advantage with re- 

 gard to the teaching and understanding of science which 

 accrues from this philosophical unification. To illustrate 

 by an example : we may assert that all equations without 

 exception which connect two or more different classes of 

 phenomena must necessarily be equations between energy 

 values, others are altogether impossible. This follows as a 

 necessary result from the fact that besides the intuitive 

 ideas of space and time, energy is the only quantity which 

 is common to each and every class of phenomena ; and 

 therefore energy quantities are the only ones which can 

 possibly be equated between these classes. 



I must, unfortunately, refrain from entering into the 



