B84 COSMIC PniLOSOPnr. [pt. il 



systems of atoms is taken for granted in every proposition of 

 chemistry ; as, for instance, when we say that it will take 

 four molecules of any monatomic substance, like hydrogen, 

 to saturate a single molecule of any tetratomic substance, 

 like carbon. Now to assert the equality of action and re- 

 action, whether between masses, molecules, or atoms, is to 

 assert that force is persistent. " The allegation really amounts 

 to this, that there cannot be an isolated force, beginning and 

 ending in nothing ; but that any force manifested, implies an 

 equal antecedent force from which it is derived, and against 

 which it is a reaction. Further, that the force so originating 

 cannot disappear without result ; but must expend itself in 

 some other manifestation of force, which, in being produced, 

 becomes its reaction ; and so on continually." x Clearly, 

 therefore, the assertion that force is persistent is the funda- 

 mental axiom of physics : it is the deepest truth which 

 analytic science can disclose. 



But now what warrant have we for this fundamental 

 axiom ? How do we know that force is persistent ? It 

 force is not persistent, if a single unit of force can ever be 

 added to or subtracted from the sum-total at any moment 

 existing, our entire physical science is, as we have seen, a 

 mere delusion. In such case, it is a delusion to believe that 

 action and reaction are always equal, that the strongest bow, 

 bent by the strongest muscles, will always send its arrow to 

 the greatest distance if otherwise unimpeded ; it is a delusion 

 to believe that the pressure of the atmosphere and its tem- 

 perature must always affect the height of enclosed columns 

 of alcohol or mercury, or that a single molecule of nitrogen 

 will always just suffice to saturate three molecules of chlo- 

 rine. And, this being the case, our concrete sciences also 

 fall to the ground, and our confidence in the stability of 

 nature is shown to be baseless ; since for aught we can say to 

 the contrary, the annihilation of a few units of the earth's 

 1 Spencer, First Principles, p. 188. 



