The Roman Inquisition's precept to Galileo (1616)

On 26 February 1616 Galileo was ordered to cease to defend heliocentrism in any way whatsoever. This order, called a precept, automatically applied to anything he might later attempt to publish on the subject. Issued at the end of his first trial by the Roman Inquisition, the precept became the spark that triggered his second trial in 1632-3 and figured importantly in the justification of his sentence. This precept has been a subject of controversy since the late nineteenth century for its authenticity, legality and legitimacy. This paper addresses the first two points and establishes the facts of what probably happened in 1616. It does so by examining seven texts that bear on the event. All but one of these (plus Galileo's first deposition in 1633) agree tolerably well that Galileo did indeed receive the precept in the strongest form. An examination of the singleton text in the context of how the Inquisition produced and kept its records as well as of its procedures and personnel shows that it is the least reliable source. This context also supports the argument that certainty about what happened is impossible to achieve. The theory that the document most damaging to Galileo was a forgery is also disposed of. Examination of the crucial phrase successive ac incontinenti in one of the documents supports the paper's suggestion that more caution is in order before accepting the currently nearly universal claim that the precept was improper in law.