338 THE POPULAR SCIENCE MONTHLY. 



Species " is not traceable ; the foremost men of science in every coun- 

 try are either avowed champions of its leading doctrines, or at any 

 rate abstain from opposing them ; a host of young and ardent investi- 

 gators seek for and find inspiration and guidance in Mr. Darwin's 

 great work ; and the general doctrine of evolution, to one side of 

 which it gives expression, finds in the phenomena of biology a firm 

 base of operations whence it may conduct its conquest of the whole 

 realm of nature. 



History warns us, however, that it is the customary fate of new 

 truths to begin as heresies and to end as superstitions ; and, as matters 

 now stand, it is hardly rash to anticipate > that, in another twenty years, 

 the new generation, educated under the influences of the present day, 

 will be in danger of accepting the main doctrines of the " Origin of 

 Species " with as little reflection, and it may be with as little justifi- 

 cation, as so many of our contemporaries, twenty years ago, rejected 

 them. 



Against any such a consummation let us all devoutly pray ; for the 

 scientific spirit is of more value than its products, and irrationally-held 

 truths may be more harmful than reasoned errors. Now, the essence 

 of the scientific spirit is criticism. It tells us that, to whatever doc- 

 trine claiming our assent, we should reply, Take it if you can compel 

 it. The struggle for existence holds as much in the intellectual as in 

 the physical world. A theory is a species of thinking, and its right 

 to exist is coextensive with its power of resisting extinction by its 

 rivals. 



From this point of view it appears to me that it would be but a 

 poor way of celebrating the Coming of Age of the Origin of Species 

 were I merely to dwell upon the facts, undoubted and remarkable as 

 they are, of its far-reaching influence and of the great following of 

 ardent disciples who are occupied in spreading and developing its doc- 

 trines. Mere insanities and inanities have before now swollen to por- 

 tentous size in the course of twenty years. Let us rather ask this 

 prodigious change in opinion to justify itself ; let us inquire whether 

 anything has happened since 1859 which will explain, on rational 

 grounds, why so many are worshiping that which they burned, and 

 burning that which they worshiped. It is only in this way that we 

 shall acquire the means of judging whether the movement we have 

 witnessed is a mere eddy of fashion, or truly one with the irreversible 

 current of intellectual progress, and, like it, safe from retrogressive 

 reaction. 



Every belief is the product of two factors : the first is the state of 

 the mind to which the evidence in favor of that belief is presented ; 

 and the second is the logical cogency of the evidence itself. In both 

 these respects the history of biological science during the last twenty 

 years appears to me to afford an ample explanation of the change 

 which has taken place ; and a brief consideration of the salient events 



