1 82 THE GRAMMAR OF SCIENCE 



of time — we measure the breadth of our field — so time 

 marks the progression of perceptions at a position in 

 space — we measure the length of our field. The com- 

 bination of the two modes, or change of position with 

 change of time, is motion, the fundamental manner in 

 which phenomena are in conception presented to us. 



If we had solely the power of perceiving coexisting 

 things, our perception might be wide, but it would fall 

 far short of its actuality. The power of " perceiving 

 things apart " by progression or sequence is an essential 

 feature of conscious life, if not of existence. Without 

 this time-mode of perception the only sciences possible 

 would be those which deal with the order or relationship 

 of coexisting things, with number, position, and measure- 

 ment — in other words, the sciences of Arithmetic, 

 Algebra, and Geometry. Bodies might have size and 

 shape and locality, but science would be unable to deal 

 with colour, warmth, weight, hardness, etc., all of which 

 sense -impressions we conceive to depend upon our 

 appreciation of sequence. In short, the physical, bio- 

 logical, and historical sciences, which have for their 

 essential topics change, or sequence in perception, would 

 be impossible. 



I have spoken of certain branches of science being 

 possible or impossible without the time-mode of percep- 

 tion. I ought rather to say that the material for these 

 branches of science can or cannot be conceived to exist 

 without time. For in truth all scientific knowledge 

 would be impossible without time ; thought undoubtedly 

 involves an association of immediate and stored sense- 

 impressions (p. 46) ; every conception, geometrical as 

 well as physical, is ultimately based on perceptual ex- 

 perience, and the very word experience connotes the 

 time-mode of perceiving things. This leads us to what 

 at first sight appears a fundamental distinction between 

 the modes space and time. Space as our method of 

 perceiving coexisting things, of distinguishing groups of 

 immediate sense-impressions, is associated with the world 

 of actual phenomena which we project outside ourselves 



