OF THE UNITY OF THOUGHT. 693 



support them. The leaders of this attack were Feuer- 

 bach, Moleschott, Biichner, and Carl Vogt. In this 

 country, on the other side, the violent spirit came from 

 the side of prominent exponents of the established 

 beliefs ; the discussion originating in the publication, 

 about the same time, of two works of very different 

 character but equally impressive by the definiteness of 

 their respective doctrines. They were Mansel's "Bampton 

 Lectures " on ' The Limits of Eeligious Thought,' and 

 Darwin's ' Origin of Species.' We know that Lotze on 

 his side took a leading part in the criticism of material- 

 ism ; we also know that Spencer was greatly influenced 

 by the ultimate conclusions drawn by Mansel from the 

 philosophy of Sir Wm. Hamilton ; further, that Darwin's 

 startling hypothesis of natural selection furnished one 

 of the most telling illustrations of the larger but vaguer 

 theory of evolution which Spencer had then already 

 clearly formulated for himself. 



The principal ideas which contributed to the formation 53. 



o f t- i t i Fonnative 



of Spencers highest scientific generalisation, and which ideas of 

 were at work in his mind before Darwin's classical treatise philosophy, 

 appeared, were partly suggested in the biological writings 

 of von Baer ; these had become known in this country 

 through Huxley's translations. To these must be added 

 the theory of environment and adaptation, and the 

 conviction that psychical and social phenomena cannot 

 be understood by the study of individuals alone, but 

 point to the history of the race. When studying the 

 phenomena of development Spencer recognised the im- 

 portance of the nebular hypothesis of Kant and Laplace 

 as an explanation of the genesis of the solar system. 



