Let us acknowledge that in truth we know nothing about anything, so far as ultimate truths are concerned. Scientifically considered nature is a riddle to which human curiosity can find no answer. Hypothesis follows hypothesis, the ruins of theories are piled one on another, but truth ever escapes us. To learn how to remain in ignorance may well be the final lesson of wisdom.[240]
XVI
THE FACTS OF EVOLUTION
LEAVING the field of speculation and "ætiology," we have now to enquire, not to what causes organic Evolution may be attributable, but how far it can be shewn to have actually occurred. This can be learnt only from the history of life upon earth as disclosed by the evidence of palæontology, or the geological record, and we are thus brought to the investigation of that evidence, by which alone, as Professor Huxley agrees, can the truth about Evolution be scientifically or satisfactorily established. In his address recently mentioned on occasion of the twenty-first birthday of the Origin of Species, having spoken of various advances of our knowledge, as in comparative anatomy and embryology, which had helped to win acceptance for transformist doctrines, he thus continued:
But all this remains mere secondary evidence. It may remove dissent, but it does not compel assent. Primary and direct evidence in favour of evolution can be furnished only by palæontology. The geological record, so soon as it approaches completeness, must, when properly questioned, yield either an affirmative[{205}] or a negative answer; if evolution has taken place, there will its mark be left; if it has not taken place, there will be its refutation.
This is common sense. Evolution can claim to be a scientific truth, only so far as clear evidence is forthcoming that Evolution there has been. If the geological record be sufficiently complete to prove or disprove its claims, the question is settled for ever. If, on the other hand, the record be not complete enough for a conclusive verdict, it is, at least, hard to understand the grounds of such a statement as that the doctrine of Evolution has long since passed beyond the stage of discussion among scientific thinkers;[241] or that of Professor Marsh, that to doubt Evolution is to doubt Science; or of Professor Huxley himself[242]—"So far as the animal world is concerned, Evolution is no longer a speculation, but a matter of historical fact."
This historical enquiry is accordingly all-important, and it is one which should be easy to undertake without any prepossessions, for it is hard to see upon what à priori grounds these could rest. That there has been Evolution in one sense of the term is obvious,—that is to say, development of organic types from lower to higher forms, from the sea-weed or fungus to the oak or the rose, from the star-fish or the coral-insect, to the eagle or to man. The question is, not whether there has been such a[{206}] progressive succession of forms, but whether one form has proceeded from another genetically, being produced in the same manner as individuals of a species now are. That this has been the case, as Professor Huxley tells us in the same address, is the cornerstone of evolutionary teaching. He appears indeed to restrict Evolution within the limits of classes and groups, but such restriction is so contrary to all his principles that the words which seem to imply it can scarcely be taken as having any definite significance. Should the appearance of different classes and groups require to be severally accounted for, we should be landed back in the system of separate creations against which he is never tired of inveighing.
The fundamental doctrine of all forms of the theory of evolution applied to biology [he says] is that the innumerable species, genera, and families of organic beings with which the world is peopled have all descended, each within its own class or group, from common parents, and have all been modified in the course of descent.
And, holding as he does that palæontology furnishes the necessary evidence, he thus continues: