The strength of the argument against chance derives, Paley tells us, from what he names “relation,” a notion akin to what some contemporary authors have named “irreducible complexity” (Behe, 1996). This is how Paley formulates the argument for irreducible complexity: “When several different parts contribute to one effect, or, which is the same thing, when an effect is produced by the joint action of different instruments, the fitness of such parts or instruments to one another for the purpose of producing, by their united action, the effect, is what I call relation; and wherever this is observed in the works of nature or of man, it appears to me to carry along with it decisive evidence of understanding, intention, art” (Paley, 1802a, pp. 175–176). The outcomes of chance do not exhibit relation among the parts or, as we might say, they do not display organized complexity. He writes that “a wen, a wart, a mole, a pimple” could come about by chance, but never an eye; “a clod, a pebble, a liquid drop might be,” but never a watch or a telescope.
Paley notices the “relation” not only among the component parts of an organ, such as the eye, the kidney, or the bladder, but also among the different parts, limbs, and organs that collectively make up an animal and adapt it to its distinctive way of life: “In the swan, the web-foot, the spoon bill, the long neck, the thick down, the graminivorous stomach, bear all a relation to one another. . . . The feet of the mole are made for digging; the neck, nose, eyes, ears, and skin, are peculiarly adapted to an under-ground life. [In a word,] this is what I call relation” (Paley, 1802a, pp. 180, 183).
Throughout Natural Theology, Paley displays extensive and profound biological knowledge. He discusses the fish’s air bladder, the viper’s fang, the heron’s claw, the camel’s stomach, the woodpecker’s tongue, the elephant’s proboscis, the bat’s wing hook, the spider’s web, insects’ compound eyes and metamorphosis, the glowworm, univalve and bivalve mollusks, seed dispersal, and on and on, with accuracy and as much detail as known to the best biologists of his time. The organized complexity and purposeful function reveal, in each case, an intelligent designer, and the diversity, richness, and pervasiveness of the designs show that only the omnipotent Creator could be this Intelligent Designer.
Paley was not the only proponent of the argument from design in the first half of the 19th century. In Britain, a few years after the publication of Natural Theology, the eighth Earl of Bridgewater endowed the publication of treatises that would set forth “the Power, Wisdom and Goodness of God as manifested in the Creation.” Eight treatises were published during 1833–1840, several of which artfully incorporate the best science of the time and had considerable influence on the public and among scientists. One of the treatises, The Hand, Its Mechanisms and Vital Endowments as Evincing Design (1833), was written by Sir Charles Bell, a distinguished anatomist and surgeon, famous for his neurological discoveries, who became professor of surgery in 1836 at the University of Edinburgh. Bell follows Paley’s manner of argument, examining in considerable detail the wondrously useful design of the human hand but also the perfection of design of the forelimb used for different purposes in different animals, serving in each case the particular needs and habits of its owner: the human’s arm for handling objects, the dog’s leg for running, and the bird’s wing for flying. “Nothing less than the Power, which originally created, is equal to the effecting of those changes on animals, which are to adapt them to their conditions.”
Paley and Bell are typical representatives of the intellectual milieu prevailing in the first half of the 19th century in Britain as well as on the Continent. Darwin, while he was an undergraduate student at the University of Cambridge between 1827 and 1831, read Paley’s Natural Theology, which was part of the university’s canon for nearly half a century after Paley’s death. Darwin writes in his Autobiography of the “much delight” and profit that he derived from reading Paley: “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 . . . his Natural Theology gave me as much delight as did Euclid. . . . I did not at that time trouble myself about Paley’s premises; and taking these on trust, I was charmed and convinced by the long line of argumentation” (Darwin, 1887a).
Later, however, after he returned from his 5-year voyage around the world in the HMS Beagle, Darwin would discover a scientific explanation for the design of organisms. Science, thereby, made a quantum leap.