RESULTS OF DARWIN'S THEORY.--The importance (for the general trend of thought) of this joint achievement of Darwin and Wallace was considerable, and could not but be regarded as an extension of the mechanical theory. The origin of species might still to some extent remain mysterious (for "natural selection" was soon realised to be only one of many factors at work in evolution), yet the area of mystery was patently reduced, and the "inexplicable" driven further back. A formula had been provided, which seemed to be as valid, and likely to prove as permanent and fruitful in biological research as Newton's law of gravity had been in the realm of physics. In point of fact, Darwin had only substituted new problems of "variation" and "heredity" for the old one of the diversity of species; but an impression was created by the new discoveries that a purely mechanical explanation of the origin of life and even of mind was within reach. THE DESCENT OF MAN.--With regard to "mind," the impression was re-inforced by Darwin's next book--the _Descent of Man_, where the gap between man and the animals was finally bridged. The work was merely an extension of the principles previously applied by him, and as a theory it had been present to Darwin's mind as far back as 1837. As soon as he had become "convinced that species were mutable productions," he could not "avoid the belief that man must come under the same law."[38] Indeed the Descent was nothing more than a corollary to the _Origin of Species_. The earlier work contains the whole of Darwinism. THE POSITION REACHED.--And with the full publication of Darwin's theories a point was reached when a more or less consistently materialistic position seemed possible. The foundations of such a position had been strengthened by the scientific atomism of Dalton, and the results of German research in the field of _organic_ chemistry seemed to open up possibilities of expressing even life in terms of matter. And, finally, the evolutionary hypothesis had reduced some of the most obscure biological problems to manageable proportions. The prospects for a purely naturalistic philosophy were phenomenally bright. CHAPTER IX MATERIALISM AND AGNOSTICISM FROM SCIENCE TO PHILOSOPHY.--The record of certain important scientific discoveries has occupied us in two recent chapters, and it is now time to examine the philosophic results that were drawn from them. It is true that the generalisations drawn from the results of scientific research were sometimes hasty, and not always sanctioned by the gifted minds to whom these results were due; yet they were assured a popular reception, and exercised an immense influence. It is not always the most accurate thinkers whose ideas gain the widest currency.