34 The Relativity of Knowledge. 



chievous fingers contain the tickle that enters the ribs. Our 

 belief one way or the other cannot alter the facts. This 

 much we can know that the proof in the case of the 

 tickle is just as strong as in the case of space and motion. 

 He who perversely asserts that the finger-tips first contain 

 the tickle that is given Uj) to the ribs, that the flea's feet 

 hold the itchiness that is given up to the back, and that the 

 knife-edge has the pain that enters the cut, is just as 

 rational as tliose who declare that the outer realities of 

 being resemble the space and motion sensations produced in 

 us by their stimulations. He who asserts that the sub- 

 stances which stimulate the nerve-centres of space and 

 motion, producing a delirium of these sensations, is like the 

 sensations themselves, has as much proof as he who holds 

 that anything we see is in any known way like the realities 

 of absolute being. Do whiskey -molecules shape themselves 

 into wriggling snakes when they enter the brain ? Do 

 Indian hemp and morphine, on entering the brain, assume the 

 forms of space, time, and actual world-objects ? Surely no 

 one will hold to a notion so crude. Yet it is not one whit 

 cruder than the current notions of men who believe that 

 the Absolute Reality, external to consciousness, can in its 

 real nature in any sense ever be known. 



The logic in both instances is positively identical. Space 

 and time, matter and motion, as known to us, are only 

 states of our own consciousness, which the actual con- 

 ditions of being tickle into perception. Whatever outer 

 reality answers to space, stirs up that feeling in us. What- 

 ever outer reality answers to motion creates in us that 

 feeling. Whatever outer reality answers to matter in- 

 duces that feeling. The outer reality bears the same rela- 

 tion to our conception of space, motion, and matter, as tlie 

 fingers, fleas' feet and knife-blade do to the tickle, itchiness 

 and pain. A picture in perspective (illustrated by stereop- 

 tieon views) will stir iTp in the proper nerve-centres a sen- 

 sation of de})th or distance in space, although we know it 

 is not the same as the outer reality that usually stirs up 

 the same feeling. We know it is on a flat surface. A 

 stereoscope will make the sensation more intense. A 

 rotating Geissler-tube, when illuminated, may be made to 

 induce the sensation of right-hand motion when really 

 rotating toward the left, or of left-hand motion when 

 whirling toward the right, or of no motion at all, when, 



