Letter of Cardinal Bellarmine to Paolo Antonio Foscarini concerning Galileo’s Theories

Explanation and Analysis of the Document

Cardinal Robert Bellarmine, one of the most influential Jesuit theologians of the seventeenth century and a member of the Congregations of the Inquisition and the Index (charged with overseeing Catholic doctrine and rooting out heresy in word and deed), wrote the letter as a reply to a treatise by the Carmelite theologian Paolo Antonio Foscarini, who, in a fashion similar to Galileo in his letter to Castelli, had argued for the compatibility of Copernican discoveries with scripture. However, Bellarmine makes it clear immediately that his remarks apply to Galileo too. After the conventional greetings, in what has sometimes been interpreted as an ironic passage, Bellarmine praises Foscarini and Galileo in that they treated the Copernican system as a mathematical hypothesis, not as absolute truth. This, the Jesuit argues, is the spirit in which Copernicus himself made his heliocentric observations, which were not meant to describe the real condition of things but merely to find a better explanation for some phenomena (“all the appearances are saved better”). It is debatable whether Bellarmine really believed that Copernicus spoke hypothetically and did not regard his system as representing the real structure of the universe. Rhetorically, Bellarmine's opening remarks on the difference between a mathematical hypothesis and an absolute, true demonstration also serve as a warning to the two addressees to conform to the official Ptolemaic and Aristotelian view of the universe. In fact, speaking of Copernicus's ideas as if they were absolute truth would both irritate theologians and harm religious faith by making “the Holy Scriptures false.”

In the second point of his argument, Bellarmine addresses Galileo's and Foscarini's argument that scripture could be interpreted in ways that would not conflict with Copernican theories. The Jesuit recalls the Canons and Decrees of the Council of Trent, which, to counter the Reformation, prohibited new readings of the scriptures that went against those of the Holy Fathers. This proscription effectively limited the possibility of personal interpretations of the texts that could not benefit from the authority of the tradition. Bellarmine explicitly states that traditional exegesis clearly places the earth at the center of the universe and conceives the sun as moving around it. Therefore, to propose a heliocentric view of the universe would be just as heretical as challenging the dogma of “the virgin birth of Christ.”

In his third and final point of the letter, Bellarmine makes recourse to the traditional Aristotelian hierarchy of knowledge, where astronomical laws proved through mathematical methods merely represent a possibility while the principles of natural philosophy are absolute and their truth does not need to be demonstrated. Bellarmine's concept of science, therefore, is radically different from the scientific practice embodied by Galileo, as the Jesuit's point of departure is not the observation of phenomena to then find a general principle of explanation. On the contrary, Bellarmine's starting point must be an absolute principle that then leads to certain consequences. While the Aristotelian view of science started from the causes to explain the effects, the new Galilean and Copernican science would follow the opposite direction. On the specific matter of heliocentrism, Bellarmine added that common sense, too, goes against it as we experience every day the fact that the earth stands still. However, some historians have interpreted this third point as treating the heliocentric view as a possibility and thus as blurring the boundaries between absolute and possible truth. This is read as an attempt by Bellarmine and the Jesuits to keep the debate with Galileo open, despite the charges of heresy that were beginning to circulate.