HERMANN VON HELMHOLTZ 



of its ancestral existence did it acquire this experi- 

 ence ? We may be able to answer this question 

 when we have full knowledge of the whole evolution 

 of insect life, but at present it is a mystery. It is 

 still more difficult to understand, on the empiristic 

 theory, how the human infant, during the first three 

 months of its life, learns to use its hands and eyes 

 for a definite purpose. Does it begin to acquire 

 knowledge by a series of more or less successful ex- 

 periments, or is there something even here, acquired by 

 long ancestral experience, that tells the child it need 

 not try to grasp the moon, while it makes a mistake 

 with the gaslight near it and burns its little fingers ? 

 Helmholtz supported the empiristic point of view 

 by questioning the correctness of Kant's ideas as to 

 the nature of space, and the a priori truth of the 

 axioms of geometry. As early as 1852, while in 

 Konigsberg, at the very university in which Kant 

 lectured for many years, Helmholtz published an 

 important lecture on the nature of human sensa- 

 tions. 1 Then he critically examined such questions, 

 in the last section of his work on physiological optics, 

 laying down the fundamental proposition, that sensa- 

 tions are for consciousness only signs, the interpretation 

 of which is given by the intelligence. For vision, 

 these signs give intensity, quality (colour), and, in 

 relation to the part of the retina affected, what he 

 terms the local sign, that is the apparent position. 



1 Whsenschaftl. Abhandlungen, Bd. ii., 9. 591. 

 2 5 8 



