eration. But this fact of growth is by no means limited to the 

 physical history of plants and animals — it is exemplified upon a 

 far more extended scale. Astronomers hold that the solar system 

 has gone through such a process, and Geologists teach that the 

 earth has had its career of evolution. Animals have a mental 

 as well as a physical development, and there is also a progress of 

 knowledge, of religion, of the arts and sciences, of institutions, 

 manners, governments, and civilization itself. 3Ir. Spencer has 

 the honour of having first established the universality of the prin- 

 ciple by which all these changes are governed. The law of evo- 

 lution, which has been hitherto limited to plants and animals, he 

 demonstrates to be the law of all evolution. This doctrine is 

 unfolded in the fii'st Essay of the present volume, and is more or 

 less fully illustrated in the others ; but it will be found elaborately 

 worked out in the second part of First Principles. 



The course of the discussion in this part of the work will be 

 best shown by enumerating the titles to the chapters, which are 

 as follows : I. Laws in General ; 11. The Law of Evolution ; III. 

 The Same continued ; lY. The Causes of Evolution ; Y. Space, 

 Time, Matter, Motion, and Force ; YI. The Indestructibility of 

 Matter ; YII. The Continuity of Motion ; Ym. The Persistence 

 of Force ; IX. The Correlation and Equivalence of Forces ; X. 

 The Direction of Motion ; XI. The Rhythm of Motion ; XH. 

 The Conditions Essential to Evolution ; XIII. The Instability of 

 the Homogeneous ; XIY. The Multiplication of Efi"ects ; XV. 

 Differentiation and Integration ; XYI. Equilibration ; XYIL 

 Summary and Conclusion. 



A moit interesting and fruitful field of thought, it will be 

 seen, is here traversed by our author, and the latest and highest 

 questions of science are discussed under novel aspects and in new 

 relations. Not only do the pages abound with acute suggestions 

 and fresh views, but the entire argument, in its leading demoU' 



