EVOLUTION THE MASTER-KEY 



only through a special formula [that of natural 

 selection], but may, after all, survive that special 

 doctrine." What is daily becoming more evident, 

 but was unrecognized by Lord Salisbury, is that 

 if the Origin of Species were consigned to oblivion 

 the creationists would not have begun to touch 

 the foundations or the superstructure of the 

 Principles of Biology, which was planned and 

 partly written before the great work of Darwin 

 appeared. As a matter of fact, the years bring 

 naught but added strength to each of these corner- 

 stones of biological science. 



In the Principles of Biology we find, in the first 

 place, what is nowhere to be found in the writings 

 of either Darwin or Huxley a systematic attempt 

 to grapple with the central question of biology, 

 the nature of life. Spencer's definition of life, 

 which, in its shortest form, is, "The adjustment of 

 inner to outer relations," is certainly the only 

 definition which has stood the test of time, and 

 notably the discovery of radium and radio-activity, 

 which form so interesting a comment on Thomas 

 Aquinas 's definition of life as "self -movement." 

 But Spencer was not the man to cheat himself 

 with words, and he fully realized that, in the last 

 resort, the nature of life is incomprehensible : " It 

 needs but to observe how simple forms of existence 

 are in their ultimate nature incomprehensible, to 

 see that this most complex form of existence is, 

 in a sense, doubly incomprehensible ; . . . only the 

 manifestations of life come within the range of 

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