ARMY SURGEON AT POTSDAM 39 



master of language : hence it may be fitly cited in this 

 connexion : 



'The principal contents of the present memoir show it to 

 be addressed to physicists chiefly, and I have therefore thought 

 it judicious to lay down its fundamental principles purely in the 

 form of a physical premise, and, independent of metaphysical 

 considerations, to develop the consequences of these principles, 

 and to submit them to a comparison with what experience has 

 established in the various branches of physics. The deduction 

 of the propositions contained in the memoir may be based on 

 either of two maxims ; either on the maxim that it is not 

 possible by any combination whatever of natural bodies to 

 derive an unlimited amount of mechanical force, or on the 

 assumption that all actions in nature can be ultimately referred 

 to attractive or repulsive forces, the intensity of which depends 

 solely on the distances between the points at which the forces 

 are exerted. That both these propositions are identical is 

 shown at the commencement of the memoir itself. Meanwhile 

 the important bearing which they have upon the final aim of 

 the physical sciences may with propriety be made the subject 

 of a special introduction. 



' The problem of the sciences just alluded to is, in the first 

 place, to seek the laws by which the particular processes of 

 nature may be referred to, and deduced from, general rules. 

 These rulesfor example, the law of the reflection and re- 

 fraction of light, the law of Mariotte and Gay-Lussac regarding 

 the volumes of gases are evidently nothing more than general 

 ideas by which the various phenomena which belong to them 

 are connected together. The finding out of these is the office 

 of the experimental portion of our science. The theoretic 

 portion seeks, on the contrary, to evolve the unknown causes 

 of the processes from the visible actions which they present ; 

 it seeks to comprehend these processes according to the laws 

 of causality. We are justified, and indeed impelled in this 

 proceeding, by the conviction that every change in nature 

 must have a sufficient cause. The proximate causes to which 

 we refer phenomena may, in themselves, be either variable 

 or invariable; in the former case the above conviction impels 

 us to seek for causes to account for the change, and thus 

 we proceed until we at length arrive at final causes which 



