284 THE POPULAR SCIENCE MONTHLY. 



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, propa- 

 gated along the nerve, and communicated to the brain. Again, on 

 feeling the sting 1 flap the insect violently away. What has caused 

 this motion of my hand ? The command to remove the insect travels 

 from the brain 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 com- 

 plete 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 consciousness enter as links into the chain of antecedence and 

 sequence which gives rise to bodily actions ? Speaking for myself, it is certain 

 that I have no power of imagining such states interposed between tlie molecules 

 of the brain, and influencing the transference of motion among the molecules- 

 The thing ' eludes all mental presentation.' Hence an iron strength seems to 

 belong to the logic which claims for the brain an automatic action uninfluenced 

 by consciousness. But it is, I believe, admitted, by those who hold the autom- 

 aton theory, that consciousness is, produced by the motion of the molecules of 

 the brain ; and this production of consciousness by molecular motion is to me 

 quite as unpresentable to the mental vision as the production of molecular 

 motion by consciousness. If I reject one result I must reject both. /, however, 

 reject neither, and thus stand in the presence of two incomprehensibles instead 

 of one incomprehensible." 



Here I secede from the automaton theory, though maintained by 

 friends who have all my esteem, and fall back upon the avowal which 

 occurs with such wearisome iteration throughout the foregoing pages ; 

 namely, my own utter incapacity to grasp the problem. 



This avowal is repeated with emphasis in the passage to which 

 Prof. Virchow's translator draws attention. What, I there ask, is the 

 causal connection between the objective and the subjective — between 

 molecular motions and states of consciousness ? My answer is : I do 

 not see the connection, nor am I acquainted with anybody who does. 

 It is no explanation to say that the objective and subjective are two 

 sides of one and the same phenomenon. Why should the phenomenon 



