124 



HABIT AND INTELLIGENCE. 



[chap. 



Addi- 

 tional 

 j)roof of 

 this. 



Touch 

 cognises 

 linear 

 magni- 

 tudes ; 

 sight 

 cognises 

 angular 

 ones ; and 

 we think 

 more 

 easHy of 

 the former 

 than of the 

 latter. 



AVords 

 denoting 

 the former 

 are 



common : 

 words 

 denoting 

 the latter 

 are tech- 

 nical. 



A being 

 with sight 

 only 

 would 

 cognise 

 only 

 angular 

 magni- 

 tude. 



Our habitual mode of thiuking of space is sucli as to 

 afford additional proof that we have our first cognition of 

 space from touch rather than from sight. The magnitudes 

 which the hand cognises and measures are linear mag- 

 nitudes : the magnitudes which the eye cognises and 

 measures are angular magnitudes. If our conception of 

 space is derived from touch, we ought to think of linear 

 magnitudes more easily than of angular ones. If, on the 

 contrary, our conception of space is derived from sight, we 

 ought to think of angular magnitudes more easily than of 

 linear ones. Now, the former of these two is the case 

 with us ; we think more easily of linear than of angular 

 magnitudes. This is the more remarkable, because, once 

 angular magnitudes are understood, they are as easy to 

 reason about as linear ones, and much easier to measure : 

 but no one clearly conceives what angular magnitudes 

 are until he has received his first lesson in mathematics ; 

 and words denoting linear magnitudes and directions are 

 abundant in colloquial language, while words denoting 

 angular magnitudes and positions are all in some degxee 

 technical. Such words as above, below, before, behind, 

 right, left, mile, and inch, belong to common language; 

 Avliile such words as altitude, azimuth, and degree, belong 

 to scientific language. To speak technically, our sponta- 

 neous thoughts of space, whether superficial or solid, are 

 always in terms of rectilinear co-ordinates, never in terms 

 of polar co-ordinates. 



Were a being with mental faculties like ours to haA^e no 

 power of moving about, and no sense except sight, it could, 

 and would, form an idea of angular magnitude, but not 

 of linear magnitude. It would see all things, as we see 

 the stars, on the surface of a hollow sphere, of which the 



one eye the ojitical apparatus for adjusting the lenses of the eye to varying 

 distances has inevitably been destroyed in the operation for cataract ; so 

 that, by the mere physical conditions of the case, there could be no power 

 of perceiving distance by the eye, until the effects of perspective were 

 learned. This is perfectly tnie as to the fact. My conviction that the 

 cognition of space is originally derived from touch, and not from sight, is 

 not grounded on any such observations, but chiefly on the reasoning in the 

 next two paragraphs, which, so far as I know, is original. 



