230 THE COMING OF AGE OF VII 
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 re- 
markable as they are, of its far-reaching influence 
and of the great following of ardent disciples who 
are occupied in spreading and developing its 
doctrines. Mere insanities and inanities have 
before now swollen to portentous 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 worshipping that which they burned, and burn- 
ing that which they worshipped. 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 favour 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 of that history will enable us — 
to understand why, if the “ Origin of Species ” ap- 
