SPACE AND TIME 191 



perception are different from ours. If we find from long 

 experience that there is in man a normal perceptive 

 faculty which co-ordinates sense-impressions in space and 

 time in the same uniform manner, then we are justified 

 in classifying the infinitesimal minority who suffer from 

 abnormal modes of perception with the ecstatic and the 

 insane. Through sickness they have lost, or through 

 atavistic tendencies they have failed to develop, the 

 normal perceptive faculty of a healthy man — the mens 

 Sana in corpore sano. 



No less valuable is the conclusion that it is idle to 

 speak of anything as existing in space or as happening 

 in time which cannot be the material of perception. 

 Whatever by its nature lies beyond sense -impression, 

 beyond the sphere of perception, can neither exist in 

 space nor happen in time. Thus the scientific conception 

 of causation, or that of uniform antecedence cannot with 

 any meaning be postulated of it — a result we have already 

 reached from a slightly different standpoint (pp. 127 and 

 156). Indeed, it seems to me that, with a clear apprecia- 

 tion of space and time as modes of perception, most 

 phases of superstition and obscurity fade into nothing- 

 ness, while the field to which the category of knowledge 

 applies is seen to be sharply defined. 



SUMMARY 



1. Space and Time are not realities of the phenomenal world, but the 

 modes under which we perceive things apart. They are not infinitely large 

 nor infinitely divisible, but are essentially limited by the contents of our 

 perception. 



2. Scientific concepts are, as a rule, limits drawn in conception to pro- 

 cesses which can be started but not carried to a conclusion in perception. 

 The historical origin of the concepts of geometry and physics can thus be 

 traced. Concepts such as geometrical surface, atom, and ether, are not 

 asserted by science to have a real existence in or behind phenomena, but are 

 valid as shorthand methods of describing the correlation and sequence of 

 phenomena. From this standpoint conceptual space and time can be easily 

 appreciated, and the danger avoided of projecting their ideal infinities and 

 eternities into the real world of perceptions. 



