28 ORIGIN OF PHYSICAL CONCEPTS 



We may remark that much the same is true of 

 the ideas of the vident. In ordinary Discourse 

 we freely employ our ideas of external objects 

 without ever attempting a detailed reproduction 

 of the visual image. Such a reproduction would 

 be both impracticable and unnecessary, and would 

 involve such a sacrifice of time as to render Dis- 

 course altogether impossible. All that the Mind 

 of the vident ordinarily grasps and utilises in his 

 discursive employment of the idea of any physical 

 thing is what we have ventured to call its dynamic 

 significance. And the very careful analysis which 

 M. Villey has made of the mental conceptions of 

 the blind clearly shows that in their case he has 

 reached exactly the same conclusion. 



Our fundamental conceptions of the external 

 world are therefore derived from and are built up 

 out of the data of our exertional Activity combined 

 with the interruptions which that Activity per- 

 petually encounters, and in which sensations arise. 

 It would indeed be a useful work of psychological 

 analysis if the conditions of exertional action were 

 carefully and systematically investigated much 

 more useful than most of the trifling experiments to 

 which psychological laboratories are usually devoted. 



The principal elements of such a scheme would 

 be 



