William Paley, though he briefly lectured on divinity at Cambridge, spent the main part of his career as a man of the cloth. He was a frequent writer of text books, and an active opponent of slavery. His talent was as a teacher, rather than as an original thinker, but his writings on ethics included much that featured in the work of the famous utilitarians of the following century.

Paley is best known for his analogical design argument, which he presented in his Natural Theology. There he likened the universe to a watch, arguing that if we were to discover a watch in a natural environment then, due to its order, complexity, and purpose, we would rightly infer that it was the work of an intelligent designer; these features are the marks of design.

The universe, Paley argued, exhibits the same order, complexity, and purpose, and so it too can be seen to have been produced by a Creator.

It is no objection to this argument, he insists, that we have no prior knowledge of how universes are made; if we had no prior knowledge of how watches were made then we would still be able to infer from their order, complexity, and purpose that they have intelligent designers.

It is also no objection to this argument that the universe contains evil, that it sometimes goes wrong; even a watch that occasionally breaks, or runs slow, can exhibit the marks of design.