Now, Darwin wrote especially for these classes, and no one knew better than he did their great prejudice on this matter. Not only had such men as Sir Charles Lyell and Sir John Herschel expressed themselves strongly against all theories of the transmutation of species, but the universal contempt and indignation of naturalists as well as theologians against _The Vestiges of Creation_, published anonymously a few years earlier, and giving a most temperate and even religious exposition of the general arguments for the universality of evolution, showed what any one might expect who advocated and attempted to demonstrate a similar theory. This accounts for Darwin writing to Sir Joseph Hooker, in 1844, of his being “almost convinced that species are not (it is like confessing a murder) immutable,” and again, in 1845, to the Rev. L. Blomefield, that he now saw the way in which new varieties become exquisitely adapted to the external conditions of life and to other surrounding beings, and he adds: “I am a bold man to lay myself open to being thought a complete fool, and a most deliberate one.” It is only by a consideration of the frame of mind of even advanced thinkers at the time Darwin was preparing his work, and remembering how small was the effect which had been produced by Buffon, Goethe, Lamarck, the author of _Vestiges of Creation_, and the earlier writings of Herbert Spencer, that we can adequately realize the marvellous work that he accomplished. Let us now briefly consider the essential nature of this new theory, which in a few brief years became the established belief of the great majority of the students of nature, and which also gave a new interest in nature to the whole thinking world. The theory of natural selection is founded upon a few groups of thoroughly ascertained and universally admitted facts, with the direct and necessary results of those facts.