80 THE PRINCIPLES OF SCIENCE. [CHAP. v. 



which contains a full description of " this specimen," as 

 furnished in the premises, but by ellipsis asserts that it is 

 gold. It will be observed that in the symbolic expression 

 (l) I have explicitly stated what is certainly implied, that 

 copper is not gold, and gold not copper, without which 

 condition the inference would not hold good. 



