The Watchmaker Analogy

The watchmaker analogy is a version of the design argument for God's existence given its best known English statement by William Paley in his 1802 book Natural Theology. Paley asks the reader to imagine crossing a heath and finding a stone, which could plausibly have lain there forever without implying any maker, against finding a watch, whose many parts are arranged and fitted together for the specific purpose of telling time in a way that, Paley argues, could not plausibly have arisen by chance, forcing the conclusion that the watch had a maker, an intelligent designer who understood its purpose and constructed it accordingly.

Paley then applies the same reasoning to living organisms, arguing that biological structures such as the eye display a comparable, indeed far greater, complexity and fittedness to purpose than any watch, and that this complexity equally implies a designer, in this case God, whose attributes as creator Paley spends the rest of the book cataloguing from the evidence of the natural world. The argument was widely taught and highly influential in English speaking Christian thought through the early nineteenth century, including on the young Charles Darwin, who read Paley admiringly as a student before his own later theory offered a very different explanation for the same observed complexity.

David Hume had already raised sustained objections to arguments of exactly this type in his Dialogues Concerning Natural Religion, published posthumously in 1779, more than two decades before Paley's book, questioning whether the analogy between a designed artifact and a natural organism is sound at all, and pointing out that apparent imperfections and suffering in the natural world sit awkwardly with an inference to a perfectly wise and benevolent designer specifically.

Charles Darwin's theory of evolution by natural selection, published in On the Origin of Species in 1859, offered the most consequential subsequent challenge, providing a mechanism, gradual variation and differential survival over long periods of time, by which complex, apparently purposeful biological structures could arise without an intending designer, which many scientists and philosophers took as removing the specific inferential force Paley's argument had relied on. The argument did not disappear from religious and philosophical discussion: twentieth and twenty first century Intelligent Design proponents, including the biochemist Michael Behe's concept of irreducible complexity, have proposed updated versions of design reasoning aimed specifically at features its proponents argue evolutionary mechanisms cannot adequately explain, versions mainstream evolutionary biology has in turn subjected to detailed scientific critique. This atlas records the argument's classical statement, its philosophical objections, and its ongoing revival as three connected but distinct chapters of one long running debate.