The Reception of the Galilean Science of Motion in Seventeenth-Century Europe (review)

Nowadays, Galileo's theory of motion is so well received that we unthinkingly ascribe a positive connotation to this book's title. Unqualified, however, reception is an ambiguous term: was it warm? delayed? smooth? hostile? Lacking our easy post-Newtonian enthusiasm, knowledgeable seventeenth-century readers of Galileo's Dialogue (1632) and Two New Sciences (1638) saw in his theory of motion multiple conceptual, mathematical, and philosophical problems.

At one end of the reception spectrum, René Descartes was a cursory reader of Galileo who doubted the empirical validity of the odd-numbers-law of free fall. Sometimes Galileo himself had downplayed empirical tests before mathematical argumentation. Even judged as pure mathematics, however, Galileo's science of motion was egregious, suspiciously treating a falling body's total speed as the sum of a number of degrees of speed. At the other end, Pierre Gassendi — who did drop weights from the mast of a moving ship and took the odd-numbers law as valid — was one of many who wondered at Galileo's silence about the cause of free fall. In short, Galileo did not always make it easy for his readers, whose furrowed brows this book explains in rich detail.

I highly recommend Carla Rita Palmerino's lucid introduction to the collection, since I cannot adequately summarize here, let alone evaluate, eleven sophisticated, high-quality analytical studies that mostly address a specialist audience. The synthetic exception is Floris Cohen's essay. He presents the Scientific Revolution as Galileo's and Kepler's bridging of the bimillennial "chasm" (95) between two approaches to nature and their progeny: the Athenian (natural philosophical) and the Alexandrian (mathematical). While Cohen's story helps him understand Descartes's reticence toward Galileo, it sells short the millennial promiscuity of natural philosophy and mathematics in medieval Arabic and Latin optics, astronomy, and astrology, to say nothing of the science of motion.

Alan Gabbey scrutinizes the expression mechanical philosophy, arguing that these Cartesian words do not refer to a philosophical program before the 1660s. Sophie Roux, who disagrees, illuminates fundamental tensions in Descartes's mechanics, especially its hermetic theoretical seal between speed and heaviness. William Shea shows how Descartes's rejection of the void ca. 1630 surprisingly led him to see both free fall as "mathematically intractable" and Galileo's solution as extreme in identifying the physical and the mathematical.

Two contributions seek to make the invisible visible. Jochen Büttner, Peter Damerow, and Jürgen Renn argue from Galileo's unpublished works that the rocky reception of Galileo's work proceeded from his contemporaries' protection of a "shared knowledge" (100) that also surfaces in Galileo's manuscripts. For his part, Enrico Giusti lets Galileo's disciples fill in the undocumented steps of Galileo's evolution and argues that Galileo had two theories of free fall.

Palmerino's study of Pierre Gassendi's correspondence challenges his proto-Newtonian image: his principle of inertia still had circular elements, and his notion of force did not yield a uniform continuous acceleration even as he sought the cause behind Galileo's odd-numbers law of free fall. Cees Leijenhorst demonstrates that Thomas Hobbes's efforts and struggles paralleled those of Gassendi: frustratingly, the impacts of bodies could not produce a uniform continuous acceleration, which Hobbes too sought to explain by both "attractive" and "impelling forces."

Wallace Hooper's useful survey of sixteenth- and seventeenth-century tidal theories from Copernicus to Wallis finds in modern science a partial (but anachronistic) vindication of Galileo's maligned tidal theory, notably his attention to the shape of sea basins in explaining tidal periods.

Christiane Vilain sees Christiaan Huygens, who generalized Galileo's relativity of motion with his own imaginary boat experiment, as offering a non-inductive, more sophisticated geometrically-oriented mechanics. Despite debts to both Galileo and Descartes...