PERCEPTION. 40.3 



yet bear no sort of resemblance to one another. 

 The tangible world has three dimensions, namely, 

 length, breadth, and thickness; the visible world 

 only two, namely, length and breadth. The objects 

 of sight constitute a kind of language, which Nature 

 addresses to our eyes, and by which she conveys 

 information most important to our welfare. As, in 

 any language, the words or sounds bear no resem- 

 blance to the things they denote, so in this par- 

 ticular language the visible objects bear no sort of 

 resemblance to the tangible objects they represent. 



The theory of Berkeley received complete con- 

 firmation by the circumstances attending the well- 

 known case, described by Cheselden, of a boy, 

 who, from being blind from birth, suddenly ac- 

 quired, at the age of twelve, the power of seeing, 

 by the removal of a cataract. He at first imagined 

 that all the objects he saw touched his eyes, as 

 what he felt did his skin ; and he was unable 

 either to estimate distances by the sight alone, or 

 even to distinguish one object from another, until 

 he had compared the visual with what has been 

 called the tactual impression. 



This theory also affords a satisfactory solution 

 of a question which has frequently been supposed 

 to involve considerable difficulty ; namely, how it 

 happens that we see objects in their true situation, 

 when their images on the retina, by which we see 

 them, are inverted. To expect that the impression 

 from an inverted image on the retina should pro- 

 duce the perception of a similar position in the 

 object viewed, is to commit the error of mistaking 

 these images for the real objects of perception ; 

 whereas they are only the means which suggest 



