This theory, which is still commonly held, was in high favour during the earlier part of the present century. In view of the great and sudden advances which physical knowledge was making, it seemed well worth while to consecrate science to the service of theology; and at the same time, in emphasizing the argument from design, theology adopted the methods of science. The attempt to discover evidences of beneficent purpose in the structure of the eye and ear, in the distribution of plants and animals over the earth's surface, in the shapes of the planetary orbits and the inclinations of their axes, or in any other of the innumerable arrangements of nature, was an attempt at true induction; and high praise is due to the able men who have devoted their energies to reinforcing the argument. By far the greater part of the evidence was naturally drawn from the organic world, which began to be comprehensively studied in the mutual relations of all its parts in the time of Lamarck and Cuvier. The organic world is full of unspeakably beautiful and wonderful adaptations between organisms and their environments, as well as between the various parts of the same organism. The unmistakable end of these adaptations is the welfare of the animal or plant; they conduce to length and completeness of life, to the permanence and prosperity of the species. For some time, therefore, the arguments of natural theology seemed to be victorious along the whole line. The same kind of reasoning was pushed farther and farther to explain the classification and morphology of plants and animals; until the climax was reached in Agassiz's remarkable "Essay on Classification," published in 1859, in which every organic form was not only regarded as a concrete thought of the Creator interpretable by the human mind, but this kind of explanation was expressly urged as a substitute for inquiries into the physical causes whereby such forms might have been originated.