150 OF LAWS IN GENERAL. 



itself only with groups of actual objects, came earlier than 

 simple arithmetic ; the rules of which deal with numbers 

 apart from objects. Arithmetic, limited in its sphere to con 

 crete numerical relations, is alike earlier and less abstract 

 than Algebra, which deals with the relations of these rela 

 tions. And in like manner, the Calculus cf Operations comes 

 after Algebra, both in order of evolution and in order of ab- 

 stractness. In Mechanics, the more concrete relations of 

 forces exhibited in the lever, inclined plane, etc., were un 

 derstood before the more abstract relations expressed in the 

 laws of resolution and composition of forces ; and later than 

 the three abstract laws of motion as formulated by Newton 

 came the still more abstract law of inertia. Similarly with 

 Physics and Chemistry, there has been an advance from 

 truths entangled in all the specialities of particular facts 

 and particular classes of facts, to truths disentangled from 

 the disguising incidents under which they are manifested 

 to truths of a higher abstractness. 



Brief and rude as is this sketch of a mental development 

 that has been long and complicated, I venture to think it 

 shows inductively what was deductively inferred, that the 

 order in which separate groups of uniformities are recog 

 nized, depends not on one circumstance but on several cir 

 cumstances. The various classes of relations are generalized 

 in a certain succession, not solely because of one particular 

 kind of difference in their natures ; but also because they 

 are variously placed in time and in space, variously open to 

 observation, and variously related to our own constitutions : 

 our perception of them being influenced by all these con 

 ditions in endless combinations. The comparative degrees 

 of importance, of obtrusiveness, of absolute frequency, of 

 relative frequency, of simplicity, of concreteness, are every 

 one of them factors ; and from their unions in proportions 

 that are never twice alike, there results a highly complex 

 process of mental evolution. But while it is thus manifest 



