Galileo: Watcher of the Skies (review)

This book is primarily an intellectual biography, but also covers most of Galileo’s personal life. Additionally, it belongs to the genre of “conjectural history,” as the author states in the introduction. However, he does not distinguish between two subgenres: plausible and implausible conjectural history. Their difference may be characterized in terms of whether the conjectures are based on such practices as exaggerations, textual misinterpretations, injudicious emphases, arbitrary assumptions, prejudicial assessments, and so forth. Unfortunately, this book exemplifies implausible conjectural history. Consider its three principal theses.

The first (pp. 56, 261–62, 266) is an account of Galileo’s attitude toward Copernicanism, claiming that he became a Copernican in the early 1590s, and the rest of his career was an attempt to prove its truth. This is an exaggeration of the fact that, since the early 1590s, Galileo was implicitly pursuing a Copernican research program—namely a general physics of moving bodies, one of whose consequences was the physical possibility of the earth’s motion.

The second major thesis (pp. 240–50) is that, although Galileo outwardly tried to appear a good Catholic, in reality he was not a Christian but privately held “esoteric” beliefs. He was allegedly a materialist, pantheist, or deist, who denied the existence of a provident personal God, the reality of salvation and redemption, and the supernatural origin of miracles. This thesis inflates the fact that Galileo was largely uninterested in theological questions and religious discussions; was usually silent about them; but was willing to pay lip service to Catholic religious doctrines and go through the motion of religious rituals, as long as the demands were not too great.

The third principal thesis attributes to Galileo a “reluctant empiricism” (p. 265): he occasionally used observations and experiments, but “chose not to become a careful experimental scientist” (p. 255), and instead practiced mostly abstraction, idealization, deduction, and speculation. This is an overstatement of the truth that Galileo was a self-reflective and critical empirical thinker, equally appreciative of observation and reason; his emphasis on active experimentation (as distinct from passive observation) and on mathematical quantification (as contrasted with qualitative thinking) were his way of judiciously combining the requirements of both observation and reason.

However, the book is not completely devoid of merit. The author displays a high degree of imaginative talent that might otherwise be put to good use. His erudition is considerable. The book is full of information that might benefit discriminating readers; they would almost certainly learn some interesting details about Galileo’s personal life that had escaped their attention. Additionally, there are at least three topics on which the book’s discussions are valuable.

This first is a critique of Paul K. Feyerabend’s claim that Galileo’s observations of the moon were inaccurate and unreliable, based on the poor quality of the lunar illustrations in The Sidereal Messenger (1610). Wootton (pp. 101–02) points out that Feyerabend used the crude illustrations found in the pirated Frankfurt edition rather than the superior ones in the original Venice edition.

A second valuable discussion involves chronological questions about the origin of the external difficulties that affected the publication, reception, and consequences of Galileo’s Dialogue on the Two Chief World Systems, Ptolemaic and Copernican (1632). The chief difficulty concerned the politics of the Thirty Years’ War and is usually connected with the events of spring and summer 1632, after the Dialogue had already been published. However, Wootton (pp. 197–200) argues that such difficulties started in summer 1630, immediately after Galileo received a tentative imprimatur.

A third valuable point is Wootton’s decision to usually refer to Galileo as a “scientist,” rather than as a (natural) “philosopher.” Wootton’s justification (pp. 259–60) is right; although the English words science and scientist stem from the eighteenth or nineteenth century, the Italian terms scienza and scienziato were already common in Galileo’s time.

Despite these useful points, nonexperts might be unable to separate the wheat from...