THE TEKCErTIOX OF SIGHT. 315 



of these is capable of innumerable different degrees of 

 sensation of one, two, or three primary colours. It 

 follows that it is possible to construct an immeasurably 

 greater number of combinations here than with the few 

 letters which build up our words. Nor must we forget 

 the extremely rapid changes of which the images of sight 

 are capable. No wonder, then, if our senses speak to us 

 in language which can express far more delicate distinc- 

 tions and richer varieties than can be conveyed by words. 



This is the solution of the riddle of how it is possible 

 to see; and, as far as I can judge, it is the only one 

 of which the facts at present known admit. Those 

 striking and broad incongruities between Sensations and 

 Objects, both as to quality and to localisation, on which 

 we dwelt, are just the phenomena which are most in- 

 structive ; because they compel us to take the right road. 

 And even those physiologists who try to save fragments 

 of a pre-established harmony between sensations and 

 their objects, cannot but confess that the completion and 

 refinement of sensory perceptions depend so largely upon 

 experience, that it must be the latter which finally 

 decides whenever they contradict the supposed congenital 

 arrangements of the organ. Hence the utmost signi- 

 ficance which may still be conceded to any such anatomi- 

 cal arrangements is that they are possibly capable of 

 helping the first practice of our senses. 



The correspondence, therefore, between the external 

 world and the Perceptions of Sight rests, either in whole 

 or in part, upon the same foundation as all our know- 

 ledge of the actual world on experience, and on constant 

 Verification of its accuracy by experiments which we 

 perform with every movement of our body. It follows, 

 of course, that we are only warranted in accepting the 

 reality of this correspondence so far as these means of 



