FORCING INTELLIGENCE 81 



The sensations of sight form organic connections 

 with hearing, smelling, tasting, by the same process 

 heretofore described as with touch. The auditory, 

 olfactory, and taste sensations are, however, for im- 

 parting conceptions or knowledge of properties, 

 dimensions, etc., greatly inferior to those of sight. 

 Their relations to the growth of human intelligence 

 is therefore disposed of, a fortiori, when that of sight 

 has been. 



The conclusion, then, is safely established, that if 

 touch had not previously made man familiar with 

 things and their qualities, the seeing only of lights, 

 shadows, and colors would give him little if any 

 knowledge of their nature, 



The feelings of muscular tension produced by 

 expansions and contractions of the iris, also those 

 caused by the shift ings of the axial direction of the 

 eyes, may seem capable of directly inducing knowl- 

 edge of size, form, etc. ; but on reflection this is per- 

 ceived to be an error. For the former movements 

 are caused by changes in the amount of intensity 

 of light, and the latter indicate relative location only, 

 so that objects differing widely in magnitude may 

 at different distances, if they subtend the same angle 

 of vision, look as if they were the same in size. A 

 line of reasoning similar to the above would apply, 

 a fortiori, to the senses of sound, smell, and taste. 

 It follows, then, that touch is the only sense by which 

 we acquire primary experience and familiarity with 

 things and their qualities. 



