How Kepler’s three laws became Kepler’s three laws

Kepler never called his three planetary laws ‘laws’, discussed them as a coherent group, stated them to be three or put them in the order that has become canonical today. When and by whom his insights were conceptualised in their modern form is an open question. Previous conjectures point to the astronomical literature of the later 18th century. By contrast, this short article tries to show that the conceptualisation of Kepler’s laws took place in the late 17th and early 18th centuries. This process was furthered by the growing popularity of the notion of ‘laws of nature’ as an epistemic category at the time. It involved Newton and Leibniz as well as the earliest authors of textbooks of Newtonian astronomy and physics.