xiv INTRODUCTION 



simple. The sense-qualities are the ultimate elements 

 of our intuition, and, as such, are quite independent 

 unities, which are indivisible, and capable of change 

 only in their intensity. Transitions, such, for instance, 

 as orange, which we find between red and yellow, 

 depend on two qualities sounding out simultaneously. 



Now Helmholtz explained the qualities as signs of 

 an external phenomenon which proceeds parallel with 

 their change. This external phenomenon remains for- 

 ever unknown to us. By his famous ''trust and act," 

 as the philosophy to be drawn from this latter con- 

 clusion, he actually declared the bankruptcy of 

 physiological psychology. 



For if the external laws of Nature are forever with- 

 drawn from our knowledge, then the proof that our 

 psyche is under their control can never be adduced. 



What Helmholtz required of us was the belief in the 

 existence of natural laws which are entirely independent 

 of us. This requirement was readily complied with. 

 For the average thinker there is an end to everything, 

 if we no longer try to believe in force and matter ! 



Up to this point the physical laws had been no more 

 than hypotheses ; now they acquired the authority of 

 an article of faith, which was enthusiastically spread 

 abroad by the lesser deities. 



But it was very unsatisfactory for research to be 

 obliged to base its entire structure on an article of faith 

 which was in no way better than the dogmas of the 

 Church. And that merely because Helmholtz saw in 

 the sense-qualities subjective signs of the actual 

 phenomenon. 



It was certainly a misleading assumption, but in no 

 way necessary. As Helmholtz himself taught, the 

 objects that surround us are constructed from the sense- 

 qualities ; and indeed, one person uses some sense- 

 qualities for the making of objects, and another uses 

 others. So for him they are nothing but signs or 

 indications for his subjective use, and they assert 

 nothing whatever with regard to a phenomenon that 

 is independent of him. 



