"PHYSIOLOGICAL" PSYCHOLOGY 485 



Thus, the " mystery " is simply held over, to he attacked by Kant, 

 in whose person eighteenth century thought was to give place to a very 

 contrasted movement. For him, space and time, the general forms 

 of human perception of all events in consciousness, are factors not 

 derived from materials supplied by sensation. They belong to the 

 unifying power of perception in its relation to objects which, again, 

 demands the presence of elements presented by sensation. Accordingly, 

 he is quite clear that, for example, geometrical truth must be classed 

 as a priori; that is, -it can not be distilled, as it were, from those sense 

 materials acquired in the course of experience. Thus Kant forces us 

 to class him as a " nativist.'' So it does not surprise us to observe that 

 he fails to envisage difficulties which were to become capital for phys- 

 iological psychology at a later time. For instance: How, as a matter 

 of fact, do we construct our completed perception of space? Granted 

 that it be the product of psychical processes, what are they ? Granted 

 that it become effective only in the presence of objects, which presup- 

 pose sensuous matter, What does this physiological reference gift to 

 our perception? Or, once more, by what subtle alchemy can we ex- 

 plain the obvious fact that we distribute our sensations in space, as it 

 were? How, that is, can we account for localization? Here we quit 

 the philosophical line for a while, observing that its unanswered ques- 

 tions will reappear in an altered perspective. 



II 



In the realm of physics, prior to the systematic inquiries of the 

 nineteenth century, several more or less sporadic references to the con- 

 nection between physical and psychical phenomena occur. Such, for 

 example, were the discussions, by Euler and Daniel Bernouilli, of " the 

 law governing the motions of strings " ; 8 Bernoulli's theory of the 

 mensura sortis, 9 with Laplace's addition of the fortune physique and 

 the fortune morale. These forecast the laws of psycho-physical rela- 

 tionship formulated by E. H. Weber and Fechner. Similarly, the dis- 

 coveries of Galvani and Yolta led to speculations on a supposed 

 parallelism between the known phenomena of electricity and the so- 

 called " discharges " of innervation which, in a way, plumbed the 

 depths of quasi-charlatanism in the developments from Mesmer, and 

 touched the heights of scientific advance in du Bois Reymond's classical 

 work " Untersuchungen iiber thierische Electricitat " (1818), where 

 the mystical and the physical views passed over into physiology for 

 systematic clarification. 



Again, Fourier's Law, that " any given regular periodic form of 

 vibration can always be produced by the addition of simple vibrations, 

 having vibrational numbers which are once, twice, thrice, four times, 



8 "The Sensations of Tone."' Hehnholtz, p. 23 ( Eng. trans.). 



9 " German Psychology of To-day," Ribot, p. 226 (Eng. trans.). 



