II 



THE ORIGIN OF PHYSICAL CONCEPTS 



" Penser c'est sentir" said Condillac. " It is 

 evident," said Bishop Berkeley, " to one who takes 

 a survey of the objects of Human Knowledge that 

 they are either ideas actually imprinted on the 

 senses or else such as are perceived by attending to 

 the passions and operations of the Mind, or lastly 

 ideas formed by help of memory and imagination 

 either combining, dividing, or barely representing 

 those originally perceived in the foresaid ways." 

 J. S. Mill tells us, " The points, lines, circles, and 

 squares which one has in his mind are, I apprehend, 

 simply copies of points, lines, circles, and squares 

 which he has known in his experience," and again, 

 " The character of necessity ascribed to the truths 

 of Mathematics and even, with some reservations 

 to be hereafter made, the peculiar certainty attri- 

 buted to them is an illusion." " In the case 

 of the definitions of Geometry there exist no 

 real things exactly conformable to the defini- 



2 



