Defending Copernicus and Galileo: Critical Reasoning and the Ship Experiment Argument

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THERE IS NO DOUBT that the most original recent works on the Galileo affair have achieved new heights of erudition, documentation, and sophistication. These achievements have been made possible by a number of circumstances: the maturation of various professional disciplines such as history of science and history of philosophy; the emergence of the new field of the scholarly study of the interactions between science and religion; and the discovery of a few new documents stemming from the Vatican Galileo Commission in 1979-1992 and from the formal opening to scholars of the Inquisition Archives in Rome since 1998.

However, with few exceptions, these scholarly works tend to exhibit several key weaknesses. One is that they usually abound in over-inflated complications, concluding little more than that the Galileo affair is more complicated than previously thought. Another scholarly weakness is historiographical: that is, studies of Galileo's trial tend to be conducted with an inadequate knowledge of previous views, whose four-century old history contains insights that are not, but should be, appropriated and updated, and errors that are often repeated instead of avoided. A third weakness is the unwillingness or inability to learn from Galileo; that is, the practice of viewing the events and documents of the Galileo affair as inert material objects that can only be understood or interpreted, rather than as human actions (and thoughts) that can be evaluated and assessed, so as to derive from them useful lessons for us today.

My investigation of this topic is animated by the desire to avoid inflated complications (while, needless to say, avoiding over-simplifications), aiming instead at a genuine and proper simplification of a bewildering mass of material; that is, it aims to articulate a simplifying synthesis, based on primary as well as secondary sources. The investigation is also animated by the desire to take into account the history of the historiography of the Galileo affair, by exploiting the insights and avoiding the errors of previous accounts. Thirdly, I do not shy away from using Galileo (his manner of thinking) as a model to be emulated, based on an accurate and correct understanding and interpretation; the understanding of the model is developed with regard to Galileo's trial (the original affair), whereas the model is then applied to the ongoing controversy about the trial (the subsequent Galileo affair). Finally, because of the features of the Galilean model as I interpret it, I follow an approach that involves defending Galileo from his many critics while mindful of the power and importance of the many objections which they advance, and similarly criticizing the Church while appreciating the power and importance of the many proclerical arguments.

In accordance with such a motivation and such an approach, I have elsewhere (1) elaborated the following detailed argument and overarching thesis. The Copernican Revolution required that the geokinetic hypothesis be not only supported with new reasons and evidence, but also defended from many powerful old and new objections (stemming from astronomical observation, Aristotelian physics, biblical texts, and traditional epistemology). This defense in turn required not only the destructive refutation but also the appreciative understanding of those objections in all their strength. One of Galileo's major accomplishments was not only to provide new evidence supporting the earth's motion, but also to show how those objections could be refuted and to elaborate their power before they were answered. In this sense, Galileo's defense of Copernicus was reasoned, critical, open-minded, and fair-minded. Now, an essential thread of the subsequent Galileo affair has been the emergence of many anti-Galilean criticisms (from the viewpoint of astronomy, physics, theology, hermeneutics, logic, epistemology, methodology, law, social sensibility, and morals), but also various defenses of Galileo. …