The book was written in the context of the natural theology tradition. In earlier centuries, theologians such as John Ray and William Derham, as well as philosophers of classical times such as Cicero, argued for the existence and goodness of God from the general well-being of living things and the physical world.
Paley's Natural Theology is an extended argument, constructed around a series of examples including finding a watch; comparing the eye to a telescope; and the existence of finely adapted mechanical structures in animals, such as joints which function like hinges or manmade ball and socket joints. Paley argues that these all lead to an intelligent Creator, and that a system is more than the sum of its parts. The last chapters are more theological in character, arguing that the attributes of God must be sufficient for the extent of his operations, and that God must be good because designs seen in nature are beneficial.
The book was many times republished and remains in print. It continues to be consulted by creationists. Charles Darwin took its arguments seriously and responded to them; evolutionary biologists like Stephen Jay Gould and Richard Dawkins continue to discuss Paley's book to respond to modern proponents with similar ideas.