THE AIM AND ACHIEVEMENTS OF SCIENTIFIC METHOD. 121 



it is not surprising that investigators have turned aside from 

 " the high priori road," and, accepting the Carnot-Clausius 

 theorem as a law of our experience which holds good of all 

 transactions in which temperature changes occur, have sought 

 to unify the phenomena of the provinces of mechanics, 

 chemistry, and physics into one science of " energetics " which, 

 contenting itself with measuring the bare faces of sensible 

 phenomena,* expressly declines to attempt to " explain " one 

 set of objective phenomena in terms of another and so comes 

 to exhibit a practice that accords with the philosophical 

 tenets of this essay. 



The essential features of this method may be summed up 

 by the statement that it seeks some principle of determining 

 equilibrium in the " configuration " of a system (taking this 

 term in the wide sense explained on p. 118) that shall be 

 equivalent to the principle of virtual velocities which is 

 fundamental in dynamics, yet shall not, like the latter, be 

 expressed in an idiom peculiar to one of the special sciences 

 whose particulars are to be related. 



The argument which seeks this goal starts from the 

 experiences summarized in Clausius' law that if a system 

 goes through a series of modifications of a reversible character 

 its entropy suffers an unique and unambiguous change which 

 depends only on the initial and final states of the system ;f 

 while if the modifications are not reversible the change of 

 entropy which would have occurred under the conditions of 

 reversibility will be exceeded by an amount which Clausius 

 called the " sum of the non-compensated transformations." J 

 If now we agree to restrict our attention to cases in which the 

 transformations occur at a constant temperature, this additional 

 quantity of entropy can be regarded as corresponding to 



* James?, " Humanism and Truth," Mind, N.S., No. 52, p. 459. 

 t Seep. 113, supra. 



| Duhem, Le Potential Thermodynamique, 1886, p. 6, from which, in 

 the main, this section is derived. 



