SPENCER'S CONTRIBUTIONS 



theless, they must always constitute a classic in 

 the history of our knowledge of life, not merely 

 because of the special points on which they illu- 

 minate the study of biology, but also as the first 

 and most complete exposition of the theory of 

 organic evolution, including the evolution of life. 

 Spencer was wise to know that he could not afford 

 to do without the assurance of experts, and so his 

 pages were read and criticised in proof by Huxley 

 and Sir Joseph Hooker, whose expert knowledge of 

 zoology and botany were thus marshalled in aid 

 of Spencer's general and philosophical treatment 

 of the problems involved. A further advantage of 

 the Principles of Biology is conspicuous to-day. 

 It is that the work x is an exposition of organic evo- 

 lution which is independent of the truth of any 

 particular explanation or series of explanations 

 of its factors. In support of this contention we 

 may read the words of Huxley when seconding 

 the vote of thanks to Lord Salisbury after his ad- 

 dress to the British Association in 1894: "If all 

 the conceptions promulgated in the Origin of Spe- 

 cies which are peculiarly Darwinian were swept 

 away, the theory of the evolution of animals 

 and plants would not be in the slightest degree 

 shaken." In this connection one may also quote 

 the words of Dr. Merz: 1 "In fact, the general 

 principles of mechanical evolution, as first sys- 

 tematized by Mr. Spencer, received recognition 



1 History of European Thought in the Nineteenth Century, 

 II., 347- 



