408 FRAGMENTS OF SCIENCE. 



praise or deserving opprobrium. In a far coarser 

 fashion this utterance of mine has been dealt with in 

 other places : it may therefore be worth while to spend 

 a few words upon it. 



The sting of a wasp at the finger-end announces 

 itself to the brain as pain. The impression made by 

 the sting travels, in the first place, with comparative 

 slowness along the nerves affected ; and only when it 

 reaches the brain have we the fact of consciousness. 

 Those who think most profoundly on this subject hold 

 that a chemical change, which, strictly interpreted, is 

 atomic motion, is, in such a case, propagated along the 

 nerve, and communicated to the brain. Again, on feel- 

 ing the sting I flap the insect violently away. What 

 has caused this motion of my hand ? The command 

 from the brain to remove the insect travels along the 

 motor nerves to the proper muscles, and, their force 

 being unlocked, they perform the work demanded of 

 them. But what moved the nerve molecules which 

 unlocked the muscle ? The sense of pain, it may be 

 replied. But how can a sense of pain, or any other 

 state of consciousness, make matter move ? Not all 

 the sense of pain or pleasure in the world could lift a 

 stone or move a billiard-ball ; why should it stir a 

 molecule ? Try to express the motion numerically in 

 terms of the sensation, and the difficulty immediately 

 appears. Hence the idea long ago entertained by 

 philosophers, but lately brought into special prominence, 

 that the physical processes are complete in themselves, 

 and would go on just as they do if consciousness were 

 not at all implicated. Consciousness, on this view, is 

 a kind of by-product inexpressible in terms of force 

 and motion, and unessential to the molecular changes 

 going on in the brain. 



Four years ago, I wrote thus : ' Do states of con- 



