108 THE DOCTRINE OF ENERGY 



though all its laws and structure could be studied 

 and derived from them. 



Berkeley, therefore, erred seriously when he 

 described the idea as a fainter sensation. Faint 

 subjective reproductions of our sensations, as of 

 blue, green, or the like, constitute a very insignificant 

 element in our mental furniture. We seldom pur- 

 sue so far into detail the ideative effort. Severely 

 and effectively as Berkeley criticised Locke's 

 account of abstract ideas, the fact remains that 

 abstraction is a primary feature of our whole con- 

 ceptual system ; and the abstractable elements of 

 the sensible presentation being the necessary 

 constituents of all ideative representation are 

 properly denominated ideal. The one element of 

 particularity which every idea lacks is the refer- 

 ence to the transmitted transmutation to which 

 the sensible phenomenon owes its origin. We derive 

 such reference to the external solely from the ob- 

 structions which our free activity encounters and 

 without which we could receive no suggestion of 

 the non-ego, and in particular no suggestion of the 

 dynamic element which fundamentally distinguishes 

 things from thoughts. The empirical content of 

 experience the so-called secondary qualities of 

 bodies are often called in their subjective aspect 

 " ideal " because the mental impression is obviously 



