ch. i.] MATTER, MOTION, AND FORCE. 285 



centrifugal force may cause us to fall upon the sun to- 

 morrow. 



But how do we know that all science is not a delusion, since 

 there still exist upon the earth's surface persons who will 

 tell us that it is so ? "Why do we so obstinately refuse to doubt 

 the constancy of the power manifested in nature ? What proof 

 have we that no force is ever created or destroyed ? 



Logically speaking, we have no proof. An axiom which 

 lies below all frameable propositions cannot be deductively 

 demonstrated. Below the world stands the elephant on the 

 back of the tortoise, and if under the tortoise w r e put the god 

 Vishnu, where is Vishnu to get a foothold ? Nor can our 

 axiom be demonstrated inductively, without reasoning in a 

 circle. We cannot adduce the observed equality of action 

 and reaction in proof of the persistence of force, because this 

 persistence is taken for granted in every observation by 

 which the equality of action and reaction is determined. 

 Obviously it is impossible to prove the truth of an axiom by 

 any demonstration in every step of which the truth of the 

 axiom must be assumed. 



But these results need not surprise or disturb us. As we 

 saw, when discussing the Test of Truth, the process of 

 demonstration, which consists in continually " merging 

 derivative truths in those wider and wider truths from which 

 they are derived," must eventually reach a widest truth, 

 which cannot be contained in or derived from any other. 

 At the bottom of all demonstration there must lie an 

 indemonstrable axiom. And the truth of this axiom can 

 only be certified by the direct application of the test of 

 inconceivability. We are compelled to believe in the per- 

 sistence of force, because it is impossible to conceive a 

 variation in the unit by which force is measured. It is 

 impossible to conceive something becoming nothing or 

 nothing becoming something, without establishing in thought 

 ail equatioo between something and nothing; and thia 



