VII. On the Knowledge of Body and Space. By H. Wedgwood, Esq., 



Christ's College, Cambridge. 



[Read March 11, 1850.] 



There is hardly a question in the entire range of mental philosophy, a satisfactory answer 

 to which would be so influential in dissipating error and in furnishing the ground of solid 

 science, as that which has for its object the origin of our notions of Body and Space. 



The problem concerning the evidence for the existence of the material world which has 

 given rise to so much ineffectual controversy and has been made the pivot of so many systems 

 of philosophy can only be solved by a detailed exposition of the intellectual action involved in 

 the apprehension of bodily existence, and the same line of inquiry is the quarter to which we 

 must look for the removal of the difficulties which encumber the outset of Geometrical reason- 

 ing and throw so great incertitude on the entire theory of demonstrative knowledge. If every 

 step in the process by which the phenomena of form and magnitude are apprehended in actual 

 existence were clearly understood, it would appear what is the ultimate object of apprehension 

 or of thought in each indivisible element of Surface and of Line (the raw materials of figure) 

 and in what variety of relation the linear and superficial element is intrinsically capable of 

 presenting itself to our imagination. Then by combining indefinite series of such elements in 

 certain relations to each other we should attain the conception and establish the fundamental 

 definition of the simplest species of Geometrical figure, as straight lines and plane surfaces ; 

 the laws of whose inmost constitution being thus laid bare should furnish us with adequate 

 grounds for the investigation of all their essential relations, when employed in the construction 

 of more complicated species of figure. 



The investigation of the primary elements of figure would carry us too far for the limits of 

 the present paper, in which we shall confine ourselves to the details of the active process by 

 which we become acquainted with the existence of body in space. 



It is hardly necessary to premise that we have no knowledge of Body by any of the five 

 senses. What I immediately perceive by sense is the sensible phenomenon itself and not the 

 bodily substance with which it may locally be connected either as proximate cause of the sen- 

 sation, or as the organ by or in which it is felt. When I suffer under toothache, or when a 

 pin is run into me unawares, the thing of which I have actual apprehension is the pain I suffer 

 and not the bodily substance of the pin or of the tooth. When a gun goes off before my 

 windows what I hear or perceive by the ear is neither the bodily gun nor the vibrations of the air 

 by which the material action is conveyed to my ear, but the sound itself. When I gaze upon the 

 stars the visible image before my eyes affords a substantive object of contemplation apart from 



