In order to pass the B.A. examination, it was, also, necessary to get up Paley's Evidences of Christianity, and his Moral Philosophy. . . The logic of this book and as I may add of his Natural Theology gave me as much delight as did Euclid. The careful study of these works, without attempting to learn any part by rote, was the only part of the Academical Course which, as I then felt and as I still believe, was of the least use to me in the education of my mind. I did not at that time trouble myself about Paley's premises; and taking these on trust I was charmed and convinced of the long line of argumentation.
Charles Darwin. Autobiography
Paley wrote several books on philosophy and Christianity, which proved extremely influential. His 1794 book A View of the Evidence of Christianity was required reading at Cambridge University until the 20th century. His most influential contribution to biological thought, however, was his book Natural Theology: or, Evidences of the Existence and Attributes of the Deity, Collected from the Appearances of Nature, first published in 1802. In this book, Paley laid out a full exposition of natural theology, the belief that the nature of God could be understood by reference to His creation, the natural world. He introduced one of the most famous metaphors in the philosophy of science, the image of the watchmaker:
. . . when we come to inspect the watch, we perceive. . . that its several parts are framed and put together for a purpose, e.g. that they are so formed and adjusted as to produce motion, and that motion so regulated as to point out the hour of the day; that if the different parts had been differently shaped from what they are, or placed after any other manner or in any other order than that in which they are placed, either no motion at all would have been carried on in the machine, or none which would have answered the use that is now served by it. . . . the inference we think is inevitable, that the watch must have had a maker -- that there must have existed, at some time and at some place or other, an artificer or artificers who formed it for the purpose which we find it actually to answer, who comprehended its construction and designed its use.Living organisms, Paley argued, are even more complicated than watches, "in a degree which exceeds all computation." How else to account for the often amazing adaptations of animals and plants? Only an intelligent Designer could have created them, just as only an intelligent watchmaker can make a watch:
The marks of design are too strong to be got over. Design must have had a designer. That designer must have been a person. That person is GOD.And, as Paley went on to argue, if God had taken such care in designing even the most humble and insignificant organisms, how much more must God care for humanity!
The hinges in the wings of an earwig, and the joints of its antennae, are as highly wrought, as if the Creator had nothing else to finish. We see no signs of dimunition of care by multiplicity of objects, or of distraction of thought by variety. We have no reason to fear, therefore, our being forgotten, or overlooked, or neglected.Paley's arguments go back to authors such as John Ray, and have had a long intellectual history, surviving to the present day in many a piece of creationist rhetoric. Yet Charles Darwin, while himself a student at Christ's College of Cambridge University, not only had to read Paley, but was deeply impressed with Paley's arguments, as the quote at the top of this page shows. Even though Paley's concept of God as a designer is very different from Darwin's theory of natural selection, Darwin took from his reading of Paley a belief in adaptation -- that organisms are somehow fit for the environments in which they live, that their structure reflects the functions they perform throughout their lives. Where natural theology ran into trouble was in explaining the many cases of apparent pain, waste, and cruelty in the living world: why would a benevolent Designer have made cats play with mice before killing them, or parasites that eat their hosts from the inside? Paley struggled to reconcile the apparent cruelty and indifference of nature with his belief in a good God, and finally concluded that the joys of life simply outweighed its sorrows. Where Darwin departed from Paley was in his concept of natural selection as a process that could produce adaptation and design without the all-encompassing intervention of a benevolent Designer.