sions. However, Darwin accomplished something much more important for intellectual history than demonstrating evolution. Indeed, accumulating evidence for common descent with diversification may very well have been a subsidiary objective of Darwin’s masterpiece. Darwin’s Origin of Species is, first and foremost, a sustained effort to solve the problem of how to account scientifically for the design of organisms. Darwin seeks to explain the design of organisms, their complexity, diversity, and marvelous contrivances, as the result of natural processes. Darwin brings about the evidence for evolution because evolution is a necessary consequence of his theory of design.

William Paley (1743–1805), one of the most influential English authors of his time, argued forcefully in his Natural Theology (1802a) that the complex and precise design of organisms and their parts could be accounted for only as the deed of an Intelligent and Omnipotent “Designer.” The design of organisms, he argued, was incontrovertible evidence of the existence of the Creator.

Paley was an English clergyman intensely committed to the abolition of the slave trade. By the 1780s, Paley had become a much sought-after public speaker against slavery. Paley was also an influential writer of works on Christian philosophy, ethics, and theology. The Principles of Moral and Political Philosophy (1785) and A View of the Evidences of Christianity (1794) earned him prestige and well-endowed ecclesiastical benefices, which allowed him a comfortable life. In 1800, Paley gave up his public speaking career for reasons of health, providing him ample time to study science, particularly biology, and to write Natural Theology; or, Evidences of the Existence and Attributes of the Deity (1802a), the book by which he has become best known to posterity and which would greatly influence Darwin. With Natural Theology, Paley sought to update the work of another English clergyman, John Ray’s Wisdom of God Manifested in the Works of the Creation (1691). But Paley could now go much beyond Ray by taking advantage of one century of additional biological knowledge. Paley’s keystone claim is that “There cannot be design without a designer; contrivance, without a contriver; order, without choice; … means suitable to an end, and executing their office in accomplishing that end, without the end ever having been contemplated” (1802a, pp. 15–16).

Natural Theology is a sustained argument for the existence of God based on the obvious design of humans and their organs, as well as the design of all sorts of organisms, considered by themselves, as well as in their relations to one another and to their environment. The argument has two parts: first, that organisms give evidence of being designed; second,