the flash of light which, to a man who has lost himself on a dark night, suddenly reveals a road which, whether it takes him straight home or not, certainly goes his way.  That which we were looking for, and could not find, was an hypothesis respecting the origin of known organic forms which assumed the operation of no causes but such as could be proved to be actually at work.  We wanted, not to pin our faith to that or any other speculation, but to get hold of clear and definite conceptions which could be brought face to face with facts and have their validity tested.  The Origin provided us with the working hypothesis we sought.  Moreover, it did the immense service of freeing us for ever from the dilemma—­refuse to accept the creation hypothesis and what have you to propose that can be accepted by any cautious reasoner?  In 1857 I had no answer ready, and I do not think that any one else had.  A year later we reproached ourselves with dullness for being perplexed with such an inquiry.  My reflection, when I first made myself master of the central idea of the Origin, was:  “How extremely stupid not to have thought of that.”  I suppose that Columbus’s companions said much the same when he made the egg stand on end.  The facts of variability, of the struggle for existence, of adaptation to conditions, were notorious enough; but none of us had suspected that the road to the heart of the species problem lay through them until Darwin and Wallace dispelled the darkness, and the beacon-fire of the Origin guided the benighted.

Whether the particular shape which the doctrine of Evolution, as applied to the organic world, took in Darwin’s hands would prove to be final or not, was to me a matter of indifference.  In my earliest criticisms of the Origin I ventured to point out that its logical foundation was insecure so long as experiments in selective breeding had not produced varieties which were more or less infertile; and that insecurity remains up to the present time.  But, with any and every critical doubt which my sceptical ingenuity could suggest, the Darwinian hypothesis remained incomparably more probable than the creation hypothesis.  And if we had none of us been able to discern the paramount significance of some of the most patent and notorious of natural facts, until they were, so to speak, thrust under our noses, what force remained in the dilemma—­creation or nothing?  It was obvious that hereafter the probability would be immensely greater, that the links of natural causation were hidden from our purblind eyes, than that natural causation should be incompetent to produce all the phenomena of nature.  The only rational course for those who had no other object than the attainment of truth was to accept “Darwinism” as a working hypothesis and see what could be made of it.  Either it would prove its capacity to elucidate the facts of organic life or it would break down under the strain.