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 
chaijim stands in the same relation to man’s tripartite nature 
that Elohirn 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 hoped, 
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 OF MATTER WITH 
respect to its rest or motion. But if it be the essence 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 
Junes, M.D., p. 35. 
