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planation than periodic miraculous intervention by creative acts which have never been parallelled within the limits of man's experience.

The scientific mind cannot believe in a series of world miracles upon the advent of new species, as a feature of the regular course of things. The mere statement of the vulgar belief in special creation is self-contradictory. It supposes an order of nature which yet is no order. It professes to satisfy man's desire to know his universe by pointing him to the unknowable. It is in fact a violation of the fundamental postulate of thought, the principle of sufficient reason, a violation which may not be obvious to the common understanding, but which is utterly antagonistic to rational knowledge. However directly we may attribute the origin of species to the action of the Divine Being, all His actions must fit into the intelligible framework of the universe. Otherwise they cannot be admitted to form part of man's conception of the cosmos. The universe in all its parts is either knowable, or it is not knowable. Ordinary minds may rest satisfied with an unintelligible universe ; but it is the postulate of science, from which no scientifically trained mind can escape, that the universe for us, our world, must be capable sooner or later of being expressed in terms of thought. Hence before Darwin's day, guesses had been made at a rational interpretation of the natural orders. No sooner had William Smith made it known that different forms of fossil remains lay embedded in the successive strata, than the necessity was felt of accounting for the transition from species to species by natural causation. Sir Charles Lyell's great principle, that the past must be explained from causes operating in the present, unless good cause can be shown to the contrary, betrays by its very terms that it had its origin in a postulate of thought. It means that an explanation of the past from the present is likely to meet the demand of reason to see and be satisfied with the sufficiency of the cause assigned; but it does not exclude a different explanation, if it commends itself better to the understanding. For many years previous to the appearance of the Origin of Species, and especially after the publication of Sir Charles Lyell's Principles of Geology, there was a growing antipathy among scientific men to the popular belief in the miraculous origin of species. Lyell himself was only delayed in extending his principle of natural origin from the inorganic to the organic world by dislike to the pithecoid origin

He strongly inclined to account for the origin of all species of living things by natural causes, although he still wished to retain the term creation for a natural process which he thought was incomprehensible. Sir John Herschel stated plainly to Lyell his belief in the possibility of new species having originated in a natural, as opposed to a miraculous process. And Huxley informs us that the leading scientists of the time preceding the appearance of Darwin's work were groping after some hypothesis accordant with Lyell's principle, that would afford clear and definite conceptions to be confronted with facts and have their validity tested by them. Such facts as variability, the struggle for existence, and adaptation to conditions, had long been patent enough ; but no one had been able to set them in such a light as to satisfy the reason that they were an adequate cause of the origin of species, or had even seriously thought of doing so. In their bewilderment, however, the scientists had no rest from the necessities of thought; and the same impulse which doubtless originated the old cosmogonies drove them unwillingly to take refuge still in the doctrine of special creation. Without the evidence which Darwin afterwards furnished, they were really powerless to satisfy their intellectual instinct by the application of Lyell's principle. They had to wait until Darwin, by his wonderful observations and

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experiments, rendered the present capable of casting light upon the past. This again shows us that the adequacy does not abide in the present merely as such. It is not mental economy merely which forbids us to draw upon the past. The present must be shown to be capable of furnishing the means of an ideal construction of the past, which will enable it to fit into the framework of our organised experi

The blind groping of the naturalists in quest of a working hypothesis is aptly described by Darwin in a letter to Hooker (Life and Letters, vol. ii. p. 80):—“It is really laughable to see what different ideas are prominent in various naturalists' minds when they speak of species. In some, resemblance is everything, and descent of little weight. In some, resemblance seems to go for nothing, and creation the reigning idea. In some, descent is the key. In some, sterility an unfailing test. With others it is not worth a farthing. In all cases I believe from trying to define the undefinable.”

Darwin himself was not aware of the real impelling motive which made him question the immutability of species, the belief he held once in common with others. It was during the interval between the writing of the two editions of his Journal that the new theory took definite form. When he asked

why the original inhabitants of the Galapagos Islands were created on the American types of organisation, he used a liberty with the action of the Creator which would never have occurred to an unscientific mind. It was the postulate of sufficient reason operating unconsciously to himself that compelled him to seek for law in the operations of the Creator. His traditional belief in the immutability of species and in special creation melted away at the first glimmer of scientific hope. So it fell to him to set down the problem in clear and distinct terms embracing in their scope the whole sentient world. And the answer he furnished is not less distinct, that through all the grades of variety, species, and genus, in all the kingdoms of nature, there is an explanation satisfactory to the reason to be got from Nature herself. According to the Malthusian law, a large proportion of the offspring of every species must prematurely perish. We may cry out against it or not, but it is universally the case that individuals tend to multiply more rapidly than the means of subsistence. The genius of Darwin seized on this fact as Newton seized on the falling apple, and solved with it the riddle of the Origin of Species. He accumulated evidence in support of his hypothesis by observation of what

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