i64 THE GRAMMAR OF SCIENCE 



perceptions, both equally factors of consciousness. 1 he 

 association is not an association of two totally diverse 

 and opposed things— matter and mind — but of the two 

 phases of perception. Groups of sense-impressions in 

 space, being conditioned by the perceptive faculty, are as 

 much a part of the sentient being as psychical processes 

 themselves. 



Logically, then, it seems that whenever we clearly 

 separate and distinguish coexisting things, we perceive 

 them under the mode space ; and perception under this 

 mode is what we ought to mean by " existence in space." 

 Yet historically the notion of space has arisen from the 

 separation and distinction of groups of sense-impressions, 

 when some one or more members in each group were due 

 to sight or touch ; for these senses are those by which 

 groups have, in the natural history of man, been first 

 perceived apart. Just as these groups of sense-impressions 

 were projected outward from our consciousness, and treated 

 as things unconditioned by our perceptive faculty, as 

 objects independent of the sentient being, so our mode of 

 perception was treated as inherent in them, and given an 

 objective existence, fossils of which are still to be found 

 in the " primeval void " of mythology and the " appalling 

 abyss " of popular astronomy. Only gradually have we 

 learnt to recognise that empty space is meaningless, that 

 space is a mode of perception — the order in which our 

 perceptive faculty presents coexistence to us. We are not 

 compelled to postulate a space outside self for phenomena, 

 and spaces inside self for memory, thought, and the 

 psychical processes, but rather we must hold that the 

 mode in which we perceive in these different fields is 

 essentially the same, and that this mode is what we term 

 space. 



^ 5. — Conceptions and Perceptions 



If such be the space of perception, we have next to 

 ask : How do we scientifically describe it ? What is 

 conceptual space — the space with which we deal in the 

 science of geometry? We have seen that our perceptive 



