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tended world, but all hopes of a logical explanation of the process 

 by which that effect is produced seemed cut off at the outset by a 

 preliminary objection. The knowledge of motion, it was said, ob- 

 viously involves the knowledge of the body moved. The conscious- 

 ness of the motion of the hand therefore implies the conception of 

 the hand itself, an object of certain shape and size. The attempt 

 to account for the notions of shape and size from the motion of the 

 hand was thus apparently stranded in a hopeless paralogism ; and so 

 insurmountable was the difficulty taken to be, that philosophers were 

 driven to imagine a second source of elementary ideas, in addition 

 to the simple apprehension of the thing conceived in actual existence, 

 maintaining that space is known to us as the condition under which 

 we perceive external things, or. as others express it, that the notion 

 of space arises in the mind on the first apprehension of body by a 

 principle of necessary judgement, which impresses upon us the con- 

 viction that all body is contained in space. 



In the paper laid before the Society, an attempt is made to show 

 the utter barrenness of this hypothesis of a necessary origin (as it is 

 called) of the idea of space ; and the main object of the paper is to 

 rest the idea on a more solid foundation, by showing the adequacy 

 of muscular exertion, in conjunction with the sense of touch, to fur- 

 nish us with complete knowledge of the material and extended world 

 by the ordinary way of actual experience. 



There are two kinds of action ; one instinctive, immediately in- 

 duced by the physical constitution of the agent independent of the 

 understanding ; the other rational, induced by the discernment of 

 some object of desire in the end to be accomplished, and of course 

 implying a previous conception of the action in question. 



Familiar instances of instinctive action are then pointed out, from 

 whence it would appear that the sensations of touch felt on contact 

 of any part of the living frame with a foreign body operate as motives 

 to instinctive exertion through the instrumentality of that part of 

 the muscular frame on which the sensible impression is made, in- 

 stinctively impelling the sentient being to muscular reaction against 

 the material cause of the sensation, or leading him to shrink from 

 it if the sensation is of a painful nature. 



Attention is directed in particular to the action of an infant in- 

 stinctively closing his hand upon a finger placed within his palm ; 

 and it is argued that the effect of such an action on his understanding 

 will be the direct apprehension of body, a complex object consisting 

 of surface (undeveloped as yet in form and magnitude) apprehensible 

 by tactual sensation ; and substance, revealed by resistance to mus- 

 cular exertion, constituting a new kind of being essentially different 

 from any of those discerned by means of the five senses. 



The relation between body and space is illustrated by comparison 

 with the case of light and darkness, the second of the two correla- 

 tives belonging in each case to Locke's class of positive ideas from 

 negative causes. As he who has once apprehended light is subse- 

 quently enabled to look for that phEenomenon in a direction from 

 whence no rays actually penetrate the eye, so, it is argued, will he 

 who has once made use of his hand in the apprehension of body be 



