THE PERCEPTION OF SPACE. 279 



ly to Experience.* The only psychic activity required for 

 this is the association of ideas.f 



But how, it may be asked, can association produce a 

 space-quality not in the things associated ? How can we 

 by induction or analogy infer what we do not already 

 generically know ? Can * suggestions of experience ' repro- 

 duce elements which no particular experience originally 

 contained ? This is the point by which Helmholtz 's ' em- 

 piristic ' theory, as a theory, must be judged. No theory is 

 worthy of the name which leaves such a point obscure. 



Well, Helmholtz does so leave it. At one time he seems 

 to fall back on inscrutable powers of the soul, and to range 

 himself with the 'jDsychicalstimulists.' He speaks of Kant 

 as having made the essential step in the matter in dis- 

 tinguishing the content of experience from that form — 

 space, course — which is given it by the peculiar faculties 

 of the mind. ^ But elsewhere, again, § speaking of sensa- 

 tion alistic theories which would connect spatially determi- 

 nate feelings directly with certain neural events, he says it 

 is better to assume only such simple psychic activities as 

 we knoiv to exist, and gives the association of ideas as an 

 instance of what he means. Later, || he reinforces this re- 

 mark by confessing that he does not see how any neural 

 process can give rise without antecedent experience to a 

 ready-made {fertige) perception of space. And, finally, in 

 a single momentous sentence, he speaks of sensations of 

 touch as if they might be the original material of our space- 

 percepts — which thus, from the optical point of vieAv, ' may 

 be assumed as given.'' '^ 



Of course the eye-man has a right to fall back on the 

 skin-man for help at a pinch. But doesn't this mean that 

 he is a mere eye-man and not a comjDlete psychologist ? In 

 other words, Helmholtz's Optics and the ' empiristic theory ' 

 therein professed must not be understood as attempts at 

 answering the general question of how space-consciousness 

 enters the mind. They simply deny that it enters with the 



* Pp. 443, 818. t P- '<'98. Cf. also Popular Scientific Lectures, pp. 301-3, 

 X P. 456; see also 428, 441. § P. 797. || P. 812. 



i Bottom of page 797. 



