Herbert Spencer and tJie Doctrine of Evolution. 529 



This change from the indefinite to the definite is shown to 

 be the accompaniment of a more essential change from the 

 incoherent to the coherent. Throughout all aggregates of 

 all orders it is proved that there goes on a process of inte- 

 gration. This process is shown to hold alike in the growth 

 and consolidation of each aggregate as well as in the growth 

 and consolidation of its differentiated parts. The law of 

 the instability of the homogeneous is also more elaborately 

 traced out. Under the head of \.\\t principle of segregation 

 it is, moreover, shown that the universal process by which, 

 in aggregates of mixed units, the units of like kinds tend 

 to gather together, and the units of unlike kinds to sepa- 

 rate, everywhere co-operates in aiding Evolution. Yet a 

 further universal law is recognized and developed the 

 law of equilibration. The question is asked, " Can these 

 changes which constitute Evolution continue without 

 limit?" and the answer given is that they cannot; but 

 that they universally tend in each aggregate toward a final 

 state of quiescence, in which all the forces at work have 

 reached a state of balance. Like the other universal pro- 

 cess, that of equilibration is traced out in all divisions of 

 phenomena. But the most important development given 

 to the doctrine of Evolution in this volume was its affilia- 

 tion upon the ultimate principle underlying all science 

 the persistence of force. It was shown that from this ulti- 

 mate law there result certain universal derivative laws, 

 which are dealt with in chapters on The Correlation and 

 Equivalence of Forces, The Direction of Motion, and The 

 Rhythm of Motion, and it was demonstrated that these 

 derivative laws hold throughout all changes, from the as- 

 tronomical to the psychical and social. It is then shown 

 that the Instability of the Homogeneous, The Multiplica- 

 tion of Effects, Segregation and Equilibration, are also de- 

 ducible from this ultimate principle of the persistence of 

 force. So that Evolution, having been first established 



