THE MIND- STUFF THEORY. 147 



them. That a unit of feeling has nothing in common with a unit of 

 motion becomes more than ever manifest when we bring the two into 

 juxtaposition." * 



And again : 



' ' Suppose it to have become quite clear that a shock in conscious- 

 ness and a molecular motion are the subjective and objective faces of 

 the same thing; we continue utterly incapable of uniting the two, so as 

 to conceive that reality of which they are the opposite faces." t 



In other words, incapable of perceiving in them any com- 

 mon character. So Tyndall, in that lucky paragraph 

 which has been quoted so often that every one knows it by 

 heart : 



"The passage from the physics of the brain to the corresponding 

 facts of consciousness is unthinkable. Granted that a definite thought 

 and a definite molecular action in the brain occur simultaneously; we 

 do not possess the intellectual organ, nor apparently any rudiment of 

 the organ, which would enable us to pass, by a process of reasoning, 

 from one to the other." | 



Or in this other passage : 



" We can trace the development of a nervous system and correlate 

 with it the parallel phenomena of s'ensation and thought. We see with 

 undoubting certainty that they go hand in hand. But we try to soar 

 in a vacuum the moment we seek to comprehend the connection 

 between them. . . . There is no fusion possible between the two classes 

 of facts — no motor energy in the intellect of man to carry it without 

 logical rupture from the one to the other." § 



None the less easily, however, when the evolutionary 

 aiHatus is upon them, do the very same writers leap over 

 the breach whose flagrancy they are the foremost to an- 

 nounce, and talk as if mind grew ovX of body in a con- 

 tinuous way. Mr. Spencer, looking back on his review of 

 mental evolution, tells us how " in tracing up the increase 



* Psychol. § 62. f lUd. % 272. 



X Fragments of Science, 5th ed., p. 420. 



§ Belfast Address, 'Nature,' August 20, 1874. p. 318. I cannot help 

 remarking that the disparity between motions and feelings on which these 

 authors lay so much stress, is somewhat less absolute than at first sight 

 it seems. There are categories common to the two worlds. Not only tem- 

 poral succession (as Helmholtz admits, Physiol. Optik, p. 445), but such 

 attributes as intensity, volume, simplicity or complication, smooth or im- 

 peded change, rest or agitiition, are habitually predicated of both physical 

 facts and mental facts. Where such analogies obtain, the things do have 

 something in common. 



