Paley’s elaborate argument was felt by the orthodox of his time to be called for, even though at this period his way of thinking was popular. The conception of the world as a vital organism was as yet, indeed, very vague, and unsupported by any detailed, scientific scrutiny of the facts of nature, but it was in the air—it had always been in the air; it always held the minds of cautious students back from a complete surrender to the facile but illusory way of thinking typified by Paley’s famous analogy of the universe and the watch. Bacon knew that species could be transformed by the action of a new environment.[4] Goethe had a clear conception of the evolution theory, based on a study of organic structure. Erasmus Darwin, in 1794, had uttered the great and final word: “The world has been generated rather than created.”[5] Lamarck’s Philosophie Zoologique was not published till 1809, nine years after Paley’s Natural Theology, but his conception of the development of special characteristics by habitual exercise and their transmission by inheritance had been freely mooted in Paley’s day, for Paley frequently takes occasion to combat it. Even the conception of natural selection as an agency in the formation of types of being may be traced in a fantastic form as far back as to Empedocles,[6] while Plato, or whoever composed a striking couplet attributed to him in the Greek Anthology, had divined the plasticity of natural forms. “Time,” he wrote, “sways the whole world; time has power in its prolonged lapse to change the names and shapes, the nature and the destiny of things.”[7]
Fifty years after the appearance of Paley’s work, the grandson of Erasmus Darwin wrote ‘No thoroughfare’ on the entrance to Paley’s line of speculation, and closed it to mankind for ever. He did this in two ways—first by marshalling from his studies of comparative anatomy and of embryology an extraordinary volume of convincing evidence for the _fact_ of the mutability of natural forms, and secondly by his attempt to establish a plausible _method_ by which the change and development of organs and types might actually have taken place. The method, summed up in the phrases ‘natural selection’ and ‘survival of the fittest,’ was what really caught the attention of the world, and gave his doctrine the wings which carried it into almost every sphere of human thought. However we take it, it was certainly an immense contribution to the organization of knowledge, but whether it is really what it first seemed to be, the basic fact at the bottom of all the phenomena of evolution, is coming to look more and more doubtful in the light of later researches.[8]