90 Chauncey Wright. [vi. 



At first sight it may seem very bold to assert that 

 in every act of our mental lives we make such a grand 

 assumption as that of the constancy of Nature ; but it 

 is very certain that, in some form or other, we do keep 

 making this assumption. Every time that the grocer 

 weighs a pound of sugar and exchanges it for a 

 piece of silver, the practical validity of the transac- 

 tion rests upon the assumption that the same lump 

 of iron will not counterbalance one quantity of sugar 

 to-day and a different quantity to-morrow ; and a 

 similar assumption of constancy in weight and ex- 

 changeability is made regarding the silver. The 

 indestructibility of matter and the continuity or 

 persistence of force are taken for granted, though 

 neither the grocer nor his customer may have received 

 enough mental training to understand these axioms 

 when stated in abstract form. Nay, more, though 

 they may be superstitious men, believing in a world 

 full of sprites and goblins,; though they may be so 

 ignorant as to suppose that, when wood is burned and 

 water dried up, some portions of matter are annihi- 

 lated, — yet in each of these little practical transac- 

 tions of life, they go upon the same assumption- that 

 the philosopher goes upon when, with his wider 

 knowledge and deeper insight, he rules out the 

 goblins and declares that no matter is ever destroyed. 



