370 Young Man couched ly Chefelden. [Book IX. 



of prefiure compared with its bulk ; of its moifture, 

 by its coldnefs, or the prefence of water ; of its foft- 

 nefs, by its yielding ; of its hardnefs, by the yielding 

 of the finger; of its figure, by applying our hands to 

 its different parts ; of diftance, by comparifon with 

 what we know to be the length of the finger, hand, 

 or arm. All our conclufions, however, are fo regu- 

 lated by previous experience, and we fo feldom trull 

 to the evidence of touch without alfo calling in the 

 afliftance of vifion, that without the latter fenfe the 

 conclufions drawn from the other would be very li- 

 mited and imperfect. Touch is the fenfe by which 

 we acquire a knowledge of the diftance of objects, 

 which, independent of experience, obtained by means 

 of this fenfe, Is not to be difcovered by vifion. This 

 circumftance was beautifully illuflrated in the cafe of a 

 young man, as- dated in Chefelden's anatomy. This 

 young man, born blind, and being fuddenly enabled 

 to fee, in confequence of a furgical operation, imagined 

 that every thing he faw touched his eyes, and it was 

 only by repeated trials of the diftance of objects, by 

 means of touch, that he was taught to correct his 

 .error. 



From this fact, however, it is not perfectly evi- 

 dent, that an infant, born with all its fenfes perfect, 

 would naturally conclude that the objects of vifion 

 touched its eyes. Might not the young man, from 

 being fo accuftomed to judge of objects by their feel, 

 or by applying them to his tongue or nofe, have ac- 

 quired the idea, that nothing could be perceived which 

 was not in contact with the body ? and thus the con- 

 clufion which he drew might really depend on the 

 affociation of ideai 



