THE TEST OF TRUTH 



alternative step is one which the mind cannot 

 take. 



Such is indeed our only warrant for that 

 most certain of all facts — the existence of our 

 own states of consciousness. If you say that 

 you have a sensation of redness, and I require 

 you to prove the statement, you can only re- 

 iterate that such is the fact, the testimony of 

 consciousness as to the existence of its own 

 states being final, and admitting of no appeal. 

 You cannot conceive it to be otherwise. Dur- 

 ing the presence of the sensation of redness 

 it is impossible for any opposite state of con- 

 sciousness, such as the sensation of blueness, to 

 emerge. With regard to the cause of the sen- 

 sation, the case is wholly different. The sen- 

 sation of redness may be due to the presence 

 of an external object from which emitted red 

 rays impinge upon the retina ; or it may be due 

 to the presence of certain foreign substances in 

 your blood which excite in the optic nerve such 

 a rate of undulation as to produce the conscious- 

 ness of red colour. AH this is matter of in- 

 ference, and must be verified by the repeated 

 application of the test of truth. But for the 

 ultimate dictum — that the given state of con- 

 sciousness exists — you have the direct warrant 

 of consciousness itself. 



In the light of this explanation, does not our 

 canon of inconceivability seem almost a truism, 



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