Finding Neptune

Kim Boström (University of Münster)

Galileo Galilei observed what we now call the planet Neptune in 1612–13, recorded its position, and took it to be a fixed star. Nearly two centuries later, William Herschel observed what we now call the planet Uranus and took it to be a comet. Yet Herschel is credited with discovering a new planet, whereas Galileo is not. Why? Both astronomers saw the relevant object. Both misclassified it. Both documented their observations. What, then, makes the difference? We argue that this puzzle reveals a missing conceptual distinction between encounter, finding, and discovery. An encounter provides perceptual access to an object. A finding occurs when an encountered element is made a subject of further determination within an ongoing inquiry, rather than simply being absorbed into an existing classificatory framework. Discovery, by contrast, is the public stabilization of such a finding. On this account, discovery presupposes finding but is not identical with it. By analyzing the Herschel/Galileo contrast and situating it alongside the later theoretical and observational work that led to the recognized discovery of Neptune, we show how locating finding between perception and discovery clarifies the structure of scientific inquiry and reframes debates in the philosophy of scientific discovery.