158 Mr WEDGWOOD, ON THE KNOWLEDGE 



all speculation as to the bodily nature of the object seen. Thus the exercise of the senses 

 displays to us five elementary modes of being logically unconnected with the notion of bodily 

 substance — five kinds of being upon which we may think independent of all intellectual refer- 

 ence to a bodily support. We have now to investigate the source of our knowledge of that 

 material and extended universe in connexion with which all the phenomena of sense are exhi- 

 bited to our apprehension, and of which the centre, to each individual, is his own living body. 



The complexity of the problem was hardly suspected by Locke. " There is no idea" he 

 says " which we receive more constantly from sensation than solidity" (or bodily substance). 

 " The idea of solidity we receive by our touch, 1 ' by the resistance, as he subsequently explains 

 it, which body opposes to manual pressure. The idea of space he supposes to be acquired 

 independently by touch and by sight, but how the same simple idea could be derived from the 

 exercise of two distinct faculties, or how far touch, as understood by him, could be considered 

 as an elementary faculty, it did not occur to him to inquire. 



The relation between visible and tangible extension was investigated by Berkeley, who 

 shewed that the fundamental standard of form and magnitude is that which is measured by the 

 hand ; our visual perceptions being mainly of importance as enabling us to judge of the corre- 

 sponding phenomena of touch. 



On closer examination the co-operation of two distinct powers became evident even in the 

 tactual apprehension of extended things, viz. first, the sense of Touch properly so called in 

 which the sentient being is no otherwise active than in adverting to the phenomena substan- 

 tively displayed by organic action ; and secondly, the muscular power exerted in moving our 

 hand over the surface, or in pressing against the solid body of which we acquire sensible expe- 

 rience. 



It was conclusively established by Reid and Thomas Brown that the phenomena of extension 

 form no part of the original information of touch independent of muscular exertion : while a logi- 

 cal difficulty was supposed to forbid the obvious and apparently the only remaining supposition, 

 that these conceptions are acquired by the motion of the hand or other organ. The knowledge 

 of the movement of the hand, it was argued, plainly involves the knowledge of the object in 

 motion, that is, the knowledge of a body of certain size, and form, and place. It would seem 

 then that in trying to account for the knowledge of space from the motion of the hand we are 

 compelled at the outset to give credit for the very notions which ought originally to arise out 

 of the experience indicated in our reasoning, and Stewart expresses his belief in the impossi- 

 bility of escape from the apparent paralogism. 



The difficulty occurred to the modern school of French philosophy under a somewhat 

 different aspect. " The utmost" says Cousin " that can be attained by touch (including the 

 power of muscular action) and sight is the knowledge of body." But all bodies are 

 endowed with a certain form and size, and occupy a certain place. The idea of space then (in 

 which those of form, and size, and place, are comprehended) is logically involved in the idea of 

 body. In the order of actual experience, on the contrary, the idea of body is antecedent to 

 that of space. We have no conception of space until we are made acquainted with body, 

 but simultaneous with the first apprehension of body the idea of space enters the mind by a 

 principle or law of the understanding in virtue of which we necessarily judge that every body 



