WORLDS OF PHYSICS AND OF SENSE 113 



question, upon which psychologists are by no means 

 agreed. But some general remarks may be made, which 

 will suffice to show the problems, without taking sides 

 on any psychological issue still in debate. 



The first thing to notice is that different senses have 

 different spaces. The space of sight is quite different 

 from the space of touch : it is only by experience in 

 infancy that we learn to correlate them. In later life, 

 when we see an object within reach, we know how to 

 touch it, and more or less what it will feel like ; if we 

 touch an object with our eyes shut, we know where we 

 should have to look for it, and more or less what it 

 would look like. But this knowledge is derived from 

 early experience of the correlation of certain kinds of 

 touch-sensations with certain kinds of sight-sensations. 

 The one space into which both kinds of sensations fit 

 is an intellectual construction, not a datum. And 

 besides touch and sight, there are other kinds of sensa- 

 tion which give other, though less important spaces : 

 these also have to be fitted into the one space by means 

 of experienced correlations. And as in the case of things, 

 so here : the one all-embracing space, though convenient 

 as a way of speaking, need not be supposed really to 

 exist. All that experience makes certain is the several 

 spaces of the several senses, correlated by empirically dis- 

 covered laws. The one space may turn out to be valid 

 as a logical construction, compounded of the several 

 spaces, but there is no good reason to assume its in- 

 dependent metaphysical reality. 



Another respect in which the spaces of immediate 



experience differ from the space of geometry and physics 



is in regard to points. The space of geometry and physics 



consists of an infinite number of points, but no one has 



ever seen or touched a point. If there are points in a 



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