THE MIND-STUFF THEORY. 165 



analogy and a priori j)robability can alone guide us. Mr, 

 Spencer assumes that the fusion must come to pass in the 

 mental world, and that the physical processes get through 

 air and ear, auditory nerve and medulla, lower brain and 

 hemispheres, without their number being reduced. Figure 

 25, on the previous page, will make the point clear. 



Let the line a — h represent the threshold of conscious- 

 ness : then everything drawn below that line will symbolize 

 a physical process, everything above it will mean a fact 

 of mind. Let the crosses stand for the physical blow^s, the 

 circles for the events in successively higher orders of nerve- 

 cells, and the horizontal marks for the fact^ of feeling. 

 Spencer's argument implies that each order of cells trans- 

 mits just as many impulses as it receives to the cells above 

 it ; so that if the blows come at the rate of 20,000 in a second 

 the cortical cells discharge at the same rate, and one unit 

 of feeling corresponds to each one of the 20,000 discharges. 

 Then, and only then, does 'integration' occur, by the 

 20,000 units of feeling 'compounding with themselves' into 

 the ' continuous state of consciousness' represented by the 

 short line at the top of the figure. 



Now such an interpretation as this flies in the face of 

 physical analogy, no less than of logical intelligibility. 

 Consider physical analogy first. 



A pendulum may be deflected by a single blow, and swing 

 back. Will it swing back tlie more often the more we multi- 

 ply the blows ? No ; for if they rain upon the pendulum too 

 fast, it will not swing at all but remain deflected in a sensi- 

 bl}^ stationary state. In other words, increasing the cause 

 numerically need not equally increase numerically the 

 effect. Blow through a tube : you get a certain musical 

 note ; and increasing the blowing increases for a certain time 

 the loudness of the note. Will this be true indefinitely ? 

 No ; for when a certain force is reached, the note, instead of 

 growing louder, suddenly disappears and is replaced by its 

 higher octave. Turn on the gas slightly and light it : 30U 

 get a tiny flame. Turn on more gas, and the breadth of the 

 flame increases. Will this relation increase indefinitely? 

 No, again ; for at a certain moment up shoots the flame 

 into a ragged streamer and begins to hiss. Send slowly 



