7 h THE POPULAR SCIENCE MONTHLY. 



been more or less directly involved in those departments of Science 

 and Philosophy which have during this period received the largest 

 share of popular attention. 



Perhaps the greatest impetus was given to the spread of the 

 doctrine about fourteen years ago, by the publication of Mr. Darwin's 

 now celebrated " Origin of Species." This volume has been followed 

 by quite a library of works and memoirs on the same subject — partly 

 scientific and partly popular. From about the same date also, Mr. 

 Herbert Spencer has been engaged in systematically elaborating the 

 principles of an all-comprehensive Evolution Philosophy, and the 

 results of his genius and labor are now undoubtedly influencing the 

 thoughts of a rapidly-widening circle of readers. Both in this coun- 

 try and abroad, the doctrine of Evolution is gradually but surely 

 gaining ground among the most reflective ; and, although many other 

 writers have been more or less influential in determining this result, it 

 has been in the main brought about by the two above mentioned. 



Evolution implies continuity and uniformity. It teaches us to 

 look upon events of all kinds as the products of continuously-oper- 

 ating causes — it recognizes no sudden breaks or causeless stoppages 

 in the sequence of natural phenomena. It equally implies that natu- 

 ral events do not vary spontaneously. It is a philosophy which 

 deals with natural phenomena in their widest sense ; it embraces both 

 the present and the far distant past. It seeks to assure us that the 

 properties and tendencies now manifest in our surrounding world of 

 things are in all respects similar to those which have existed in the 

 past. Without a basis of this kind, the Evolution hypothesis would 

 be a mere idle dream. Uniformity is for it an all-pervading neces- 

 sity. Starting from facts of daily observation and from scientific 

 experiments, the properties and tendencies of things are noted and 

 grouped ; while philosophers, using the knowledge thus gained, seek 

 to trace back the progress of events and show how this complex 

 world has gradually been derived from a world of more and more 

 simple composition. We are taken back in imagination even much 

 farther. We are referred to a primal haze or nebula — as the gigantic 

 germ of a future Universe. This was the conception of Laplace. 



But whether we follow the philosopher in his bold speculatious 

 concerning the past, or listen to the biologist making his predictions 

 concerning the future stages which the germ of a given animal will 

 pass through in the progress of its evolution — in each case the 

 " uniformity of Nature " is tacitly assumed. This assumption under- 

 lies almost all our thoughts and actions, even in every-day life. And, 

 without such a belief in the Uniformity of Nature, science would be 

 impossible — the very idea of it, in fact, could never have arisen. In 

 its absence we could neither fathom the past nor illumine the future. 

 As Mr. Mill said ' — " Were we to suppose (what it is perfectly possi- 



1 " System of Logic," sixth edition, vol. n., p. 98. 



