man from any inferior animal whatever is absolutely incom- 

 patible with a belief of the existence in man of an immortal 

 spirit ; for by no conceivable process can that which is essen- 

 tially not material be developed from any combination of mere 

 material elements. It is nowhere stated of any inferior animal 

 that "God breathed into his nostrils the breath of lives'^; and 

 it may not unreasonably be assumed that the plural noun 

 chayim stands in the same relation to man's tripartite nature 

 that Elohim does to the tripartite existence of the Godhead. 



4. Before proceeding in an attempt to confirm the principle of 

 the conservation of energy to the satisfaction, it may be iioped, 

 of even the writers of the above essays, it is quite necessary to 

 come to a distinct understanding as to the precise meaning of 

 the terms employed, and especially those of " Force and 

 " Energy/^ since the writer has seen reason to modify in some 

 measure the views on this subject expressed in the introduction 

 to the last edition of his ^' Elements of Natural Philosophy.^'' 



5. The commonly received relative signification of the terms 

 " Force and " Energy is of considerable antiquity ; the 

 terms dynamis and energeia are employed in the ethics of 

 Aristotle, and may perhaps be best represented by the terms 

 " potentiality and actuality/' related as that which has the 

 power of producing activity is to that which acts. 



6. The usual definition of force is, that which produces or 



TENDS TO PRODUCE CHANGE IN THE STATE OY MATTER WITH 



RESPECT TO ITS REST OR MOTION. But if it bc the cssencc of a 

 definition, that while it comprehends the predicate or thing 

 defined it excludes all else, then this definition is open to grave 

 objections; it is perfectly true that force will produce or tend 

 to produce, &c., but the inverse proposition, viz., " that which 

 produces, or tends to produce,^' &c., is necessarily force, is by 

 no means equally true, for " change in the state of matter with 

 respect to its rest or motion may be produced by other matter 

 in motion (and therefore possessing energy) without the 

 intervention of any force. This definition, therefore, appears 

 to the writer as tending to confound ''force'' and "energy." 



7. Force has been thus defined by our ablest recent master of 

 experimental physics* : — '* What I mean by the word force is 

 the source or sources of all possible actions of the particles or 

 materials of the universe.'' But this definition is open to 

 much the same objection as the former, because the " source 

 of possible actions " of matter is not necessarily force. Both 



* Faraday MSS. Croonian Lectures on Matter and Force, by H. Bence 

 Jones, M.D., p. 35. 



