THE SENSATION OF SIGHT. 269 



found that by means of so inconstant a system of signs, 

 we are able to accomplish the most important part of our 

 task — to recognise the same proper colours wherever they 

 occur ; and, considering the difficulties in the way, it is 

 surprising how well we succeed. Out of this inconstant 

 system of brightness and of colours, varying according to 

 the illumination, varying according to the fatigue of the 

 retina, varying according to the part of it affected, we are 

 able to determine the proper colour of any object, the one 

 constant phenomenon which corresponds to a constant 

 quality of its surface ; and this we can do, not after long 

 consideration, but by an instantaneous and involuntary 

 decision. 



The inaccuracies and imperfections of the eye as an 

 optical instrument, and those which belong to the image 

 on the retina, now appear insignificant in comparison with 

 the incongruities which we have met with in the field of 

 sensation. One might almost believe that Nature had 

 here contradicted herself on purpose, in order to destroy 

 any dream of a pre-existing harmony between the outer 

 and the inner world. 



And what progress have we made in our task of ex- 

 plaining Sight ? It might seem that we are farther off 

 than ever ; the riddle only more complicated, and less 

 hope than ever of finding out the answer. The reader 

 may perhaps feel inclined to reproach Science with only 

 knowing how to break up with fruitless criticism the fair 

 world presented to us by our senses, in order to annihi- 

 late the fragments. 



Woe ! woe ! 



Thou hast destroyed 



The beautiful world 



With powerful fist ; 



In ruin 'tis hurled, 



By the blow of a demigod shattered. 



