THE AIM AND ACHIEVEMENTS OF SCIENTIFIC METHOD. 13 



" a natural fallacy of ordinary thinking " to credit such 

 changes in colour to the things themselves. 



But it is possible to confront the view that secondary 

 qualities exist otherwise than as the contents of our per- 

 ceptions with greater difficulties than these. It is a familiar 

 fact that if a cyclist, A, rings his bicycle bell, B, whom he is 

 approaching, and C, from whom he is separating, hear different 

 notes notes which are respectively higher and lower in pitch 

 than the note which A hears constantly, and all three persons 

 would hear if he were stationary. Can it be said that the 

 bell is actually " emitting " these three notes simultaneously 

 (not to mention the indefinite number of other notes which 

 might be heard at the same moment by different passers by) 

 but that only one of them is heard by each of the persons 

 concerned ? It must be admitted that the " plain man " who\ 

 had found no offence in the thought that the same substance 

 might be of different colours at different times under different 

 circumstances would probably be alarmed at finding himself 

 \ thus committed to the opinion that the same bell was giving 

 out to different observers different notes at the same time. 



The moment at which this discovery was made would be the 

 moment at which a philosopher, cynically contemptuous of the 

 " plain man's " confidence in his view of the world, would choose 

 to point out to him that the thing which is hot or heavy to one 

 man may be cold or light to another and would ask him whether 

 ^ he supposed that the hotness (or heaviness) could exist at the 

 .same time in the same place as the coldness (or lightness). 



To meet these difficulties the " plain man " would have to 

 become, himself, something not very different from a philosopher, 

 .and reply that these apparently inconsistent objects of sensation 

 ^ do all exist and, for that matt er K in the same place, just as the 

 different shapes of the plate all exist in the same place, although 

 from each single point only one of them can be perceived. 

 Here an indubitable philosopher might take up the "plain 

 man's " case. Things which " have " the primary and secondary 



