466 CONCLUSION. 



specified. It has recently been objected that this is an 

 unsafe method of arguing ; but it is a method used in 

 judging of the common events of life, and has often been 

 used by the greatest natural philosophers. The undulatory 

 theory of light has thus been arrived at ; and the belief in 

 the revolution of the earth on its own axis was until lately 

 supported by hardly any direct evidence. It is no valid 

 objection that science as yet throws no light on the far 

 higher problem of the essence or origin of life. Who can 

 explain what is the essence of the attraction of gravity ? 

 No one now objects to following out the results consequent 

 on this unknown element of attraction ; notwithstanding that 

 Leibnitz formerly accused Newton of introducing " occult 

 qualities and miracles into philosophy." 



I see no good reasons why the views given in this volume 

 should shock the religious feelings of any one. It is satis- 

 factory, as showing how transient such impressions are, to 

 remember that the greatest discovery ever made by man, 

 namely, the law of the attraction of gravity, was also 

 attacked by Leibnitz, " as subversive of natural, and infer- 

 entially of revealed, religion." A celebrated author and 

 divine has written to me that " he has gradually learned to 

 see that it is just as noble a conception of the Deity to 

 believe that He created a few original forms capable of 

 self-development into other and needful forms, as to believe 

 that He required a fresh act of creation to supply the voids 

 caused by the action of His laws." 



Why, it may be asked, until recently did nearly all the 

 most eminent living naturalists and geologists disbelieve in 

 the mutability of species ? It cannot be asserted that or- 

 ganic beings in a state of nature are subject to no varia- 

 tion ; it cannot be proved that the amount 'of variation in 

 the course of long ages is a limited quantity ; no clear dis- 

 tinction has been, or can be, drawn between species and 

 well-marked varieties. It cannot be maintained that spe- 

 cies when intercrossed are invariably sterile and varieties 

 invariably fertile; or that sterility is a special endowment 

 and sign of creation. The belief that species were immut* 

 able productions was almost unavoidable as long as the his- 

 tory of the world was thought to be of short duration ; and 

 now that we have acquired some idea of the lapse of time, 

 we are too apt to assume, without proof, that the geo- 

 logical record is so perfect that it would have afforded us 

 plain evidence of the mutation of species, if they had under 

 cone mutation. 



