Discussing Tides Before and After Newton: Roger Joseph Boscovich’s De aestu maris

Abstract The causes of tidal motions were widely debated from antiquity up to the eighteenth century. These discussions got a second wind in the early modern period, in the wake of a growing number of cosmological alternatives that challenged the dominant Aristotelian-Ptolemaic stance. The 1687 publication of Isaac Newton’s Principia Mathematica was a defining moment in the discussions and consequently made universal gravitation the most credible and generally accepted explanation. This paper investigates the aftermath of Newton’s discovery and demonstrates how his understanding of tidal motion crowded out competing theories within a broader European context. My main point of reference is Roger Boscovich’s De aestu maris (1747). In his work, the leading Jesuit scholar of the time contrasted Newton’s interpretation to those of other major authorities, namely Johannes Kepler, Galileo Galilei, and René Descartes, and went on to claim the superiority of the British scientist’s achievements over anything written prior to the Principia. As this essay argues, alongside a significant body of literature produced under the umbrella of the Jesuit order, Boscovich’s De aestu maris subsequently contributed to the formation of the popular image of Newton as a “scientific hero.”