SPACE AND TIME i8i 



expressed with regard to the concepts of science, he will 

 never consider that science reduces the universe to a 

 " dead mechanism " by asserting a reality for atom or 

 ether or force as the basis of sense-impression. Science, 

 as I have so often reiterated, takes the universe of per- 

 ceptions as it finds it, and endeavours briefly to describe 

 it. It asserts no perceptual reality for its own shorthand. 

 One word more before we leave this space of concep- 

 tion, separated by continuous boundaries in the eye of 

 the geometrician, peopled with atoms and ether by the 

 mind of the physicist. How, if geometrical surface, if 

 atom and ether have no perceptual reality, has the mind 

 of man historically reached them ? I believe by carrying 

 to a limit in conception processes which have no such 

 limit in perception. Preliminary stages in comparison 

 show apparent sameness and continuity, where more 

 exact and final stages show no such limit ; hence arises 

 the conception of continuous boundaries. The atom 

 again is a conceptual limit to the " moving bodies " of 

 perception ; while the ether possesses an elasticity, which 

 we have never met with in the elastic bodies of our per- 

 ceptual experience, but which is a purely conceptual limit 

 to the type of elastic substances with which we are 

 directly acquainted. These concepts themselves are a 

 product of the imagination, but they are suggested, almost 

 insensibly suggested, by what we perceive in the world of 

 phenomena. 



§ 12. — Time as a Mode of Perception 



I have dealt at greater length with space than it will 

 be necessary to deal with time, for much that has been 

 said in the former case as to perception and conception 

 will directly apply to the latter. Space and time are so 

 similar in character, that if space be termed the breadth, 

 time may be termed the length of the field of perception. 

 As space is one mode in which the perceptive faculty 

 distinguishes objects, so time is a second mode. As 

 space marks the coexistence of perceptions at an epoch 



