The main argument, which at first appears to be thus set aside, is that which is founded on the marks of design, and which is worked out in his own way with marvellous skill by Paley in his Natural Theology.  Paley’s argument rests as is well known on the evidence of design in created things, and these evidences he chiefly finds in the frame-work of organised living creatures.  He traces with much most interesting detail the many marvellous contrivances by which animals of various kinds are adapted to the circumstances in which they are to live, the mechanism which enables them to obtain their food, to preserve their species, to escape their enemies, to remove discomforts.  All nature thus examined, and particularly all animated nature, seems full of means towards ends, and those ends invariably such as a beneficent Creator might well be supposed to have in view.  And whilst there is undeniably one great objection to his whole argument, namely that the Creator is represented as an Artificer rather than a Creator, as overcoming difficulties which stood in His way rather than as an Almighty Being fashioning things according to His Will, yet the argument thus drawn from evidence of design remains exceedingly powerful, and it has always been considered a strong corroboration of the voice within which bids us believe in a God.  Now it certainly seems at first as if this argument were altogether destroyed.  If animals were not made as we see them, but evolved by natural law, still more if it appear that their wonderful adaptation to their surroundings is due to the influence of those surroundings, it might seem as if we could no longer speak of design as exhibited in their various organs; the organs we might say grow of themselves, some suitable, and some unsuitable to the life of the creatures to which they belonged, and the unsuitable have perished and the suitable have survived.

But Paley has supplied the clue to the answer.  In his well-known illustration of the watch picked up on the heath by the passing traveller, he points out that the evidence of design is certainly not lessened if it be found that the watch was so constructed that, in course of time, it produced another watch like itself.  He was thinking not of Evolution, but of the ordinary production of each generation of animals from the preceding.  But his answer can be pushed a step further, and we may with equal justice remark that we should certainly not believe it a proof that the watch had come into existence without design if we found that it produced in course of time not merely another watch but a better.  It would become more marvellous than ever if we found provision thus made not merely for the continuance of the species but for the perpetual improvement of the species.  It is essential to animal life that the animal should be adapted to its circumstances; if besides provision for such adaptation in each generation we find provision for still better adaptation in future generations,