Deism and the Watchmaker Analogy

The watchmaker analogy begins with a simple observation. The parts of a watch work together to tell the time, and their arrangement gives us reason to infer that someone designed it. If living things or the universe also contain parts that work together, can we draw the same conclusion about their origins? William Paley and the speakers in David Hume’s Dialogues Concerning Natural Religion help explain the appeal of that inference and the limits of what it can establish. Paley, Natural Theology · Hume, Dialogues, Part II

Paley’s watch on the heath

In the opening of Natural Theology, first published in 1802, Paley asks readers to imagine finding a stone while walking across a heath. Its presence prompts little immediate inference about who put it there. A watch found in the same place invites inspection. Its spring drives a chain and a series of wheels, the wheels regulate the movement of a pointer, and the glass lets someone read the dial. Changing the shape or position of the parts could stop it working. Paley argues that their fit for a specific task gives us grounds for inferring that one or more makers understood and intended that use. A watch that sometimes runs slow still has the arrangement he wants readers to notice. Paley, chapter I

Paley applies the reasoning to the eye in chapter III. The eye and a telescope can both bring rays of light to a focus. In the eye the focused image falls on the retina. Paley takes this similarity of means and function to support an inference to intelligence in nature. His book then makes further arguments about the personality, unity and goodness of God. Those chapters show that his project extends beyond the claim that there was a maker. Paley, chapters III and XXIII–XXVI

Hume’s comparison between a house and a universe

Hume’s Dialogues, published in 1779, gives the speakers different views. Cleanthes argues that nature resembles a machine made up of many smaller mechanisms. He reasons that similar effects warrant an inference to similar causes and concludes that the source of the world’s order bears some resemblance to an intelligent mind. To illustrate his point, he compares stairs suited to human legs with legs suited to walking and climbing. The fit between a structure and what it enables is where he places the weight of the argument. Hume, Part II, sections 5–9

Philo answers that the strength of an analogy depends on how closely the cases resemble each other. When we see a house, our conclusion that people built it is supported by experience of other houses and how they are made. The universe presents a different evidential situation. Experience of construction within it supplies no comparable record of universes being made. Philo challenges Cleanthes to explain why the fit he observes warrants the same confidence as the ordinary inference about a house. Hume, Part II, sections 7–8 and 17–24

What an inference to design leaves open

In Part V, Philo grants the analogy for the sake of argument and asks how much it could establish. A ship may be the work of several people. Its design can also reflect knowledge acquired by earlier builders, so the finished product gives only limited information about any one worker. Even if the universe pointed to intelligence, Philo asks how its order could settle whether one being or several were responsible, or whether the power behind it was unlimited. This is a separate problem from deciding how much the world resembles a machine. Hume, Part V, sections 5–9

The watch analogy also leaves open whether a maker would continue to act in the world. An inference about how something came to be requires additional premises to support a claim about what its maker does afterward. Deism raises another question about evidence, namely whether reason and experience can establish religious truths independently of reports of divine revelation. The overview of deism and revelation follows that debate through Tindal and Paine. Paley, chapters I and XXIII–XXVI · Hume, Part V

Conclusion

Paley’s watch makes the design argument concrete by directing attention to how parts serve a function. Hume’s dialogue tests the reasoning at two points. It asks how much the familiar case of human craftsmanship tells us about the origin of nature and how much a proposed cause would tell us about the maker. The first question concerns the strength of the analogy. The second concerns what follows from it, including whether it supports the picture of a single creator who lets the world run on its own.

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