1885.] on how Thought presents itself in Nature. 195 



Postscript. 



It may be useful to give a recapitulation of tlie main steps of the 

 argument. 



A small j)art of what takes place in the outer world affects my 

 senses, and througli them indirectly affects me. 



The result of a successful scrutiny of what is going on in the 

 outer world may for convenience be called the z part of the scientific 

 explanation of what I vvitness. 



The result of a successful scrutiny of the change which the z 

 occasions within my organs of sense would be the y part of the 

 explanation. 



The result of a successful scrutiny of the changes that ensue 

 along the associated nerves would be the x part of the explanation. 



And, finally, the result of a successful scrutiny of the physical 

 changes which this x produces within my brain would be the iv part 

 of the explanation ; and the explanation of the phenomenon from the 

 naturalist's point of view would be then complete. 



The state of my own mind while I am witnessing what is going 

 forward consists of sensations, perceptions, and conceptions, or some 

 combination of these with reflections, reminiscences, associations, 

 feelings, emotions, and so on, and may be called the a part of the 

 inquiry, as it is the known part, known as fully before as after the 

 investigation. 



The whole of a scientific inquiry starts with this a, and is concerned 

 in discovering the z, the ?/, the x, and the ii\ 



We now know enough of this class of investigation to assure us 

 that the whole of the z explanation, the y exj)laiiation, the x and the iv, 

 would, if we could fully explore them, turn out to be motions, and 

 the laws that govern changes of motion. That, for example, the 

 geranium 1 am now looking at, is a mass of molecular motions 

 (whether with, as many people suppose, or Avithout, as I suppose, that 

 'something else' which they call substance); that the molecular 

 motions in the geranium modify the ether motions going on around 

 it in the room ; that the etherial motions when thus altered produce 

 new motions in the back of my eye ; that this event next alters motions 

 in the associated nerve ; and, finally, that the disturbance in the nerve 

 produces an effect upon the motions going on in my brain. Here, if 

 all the details were ascertained, as to what particular motions arc 

 occurring at each step, ' and what laws regulate their occurrence, 

 Natural Science would have said her whole say. It has, however, 

 then to be added that although this series is self ccmtained and com- 

 plete, there occurs another event alongside of it without any traceable 

 place in the sequence of causes and effects, viz. the change within my 

 mind which I call perceiving the geranium. Herein lies the great 

 difficulty of the dualistic hypothesis, from which the monistic hypo- 

 thesis is free. 



Motion throughout this statement has meant, not my perception 



o 2 



