Jesuit Science: Does it work? Riccioli’s Case

The Society of Jesus was founded in 1540 by Ignatius Loyola to propagate and defend the faith and progress of souls in Christian life and doctrine, and such that its charter of the order, Formula of the Institute contained a number of Rules for Thinking with the Church. There, the basic attitude towards the Church was clearly elucidated. The members of the society were called Jesuits, and they developed a particular interest in experimental science and rational investigation of natural phenomena.

For instance, it was Giovanni Battista Riccioli (1598-1671), and not Galileo or Descartes, who first accurately determined the rate of acceleration for a freely falling body. One unique methodology employed by the Jesuit scientists was probabilism. It stated that “an action could be deemed moral [or correct] if at least one respectable authority had judged it so, even if his opinion was less probably than that of authorities who denied its morality.” Thus, Riccioli maintained that “The probability of an opinion remains as long as the opposite is not evidently known,” and hence “an opinion was not to be dismissed simply because the opposite was possible and even apparently supported by some evidence.” When the motion of the sun was observed, Riccioli hence concluded that, even though reason clearly convinced him that the sun is immobile while the earth is in motion, “one is not allowed to say… it is not impossible for human senses to be wrong” and pretend to ignore the sense evidence that the sun is moving. This philosophy of his put him in a unique position where he knows what reason tells him is probable but also knows sense-data are equally reliable, and hence cannot be dismissed easily. He refused to conclusively agree either with heliocentric view or with geocentric system of the universe on the basis that neither hypothesis offered definitive proof. What happens, then, when two opposing hypotheses are of equal weight? His solution was that “authority alone could settle the question.” In this dispute, he was content that “the principles of the Catholic faith provided ‘certainty without evidence,’” and opted out for the heliocentric system. But what happens if the Church condemns the probabilism? In fact, thinkers like Pascal criticized Jesuits heavily for their commitment to probabilism. Even though the Church frowned upon the practices of probabilism, probabilistic aspect of Jesuit science did not cease away, as one might expect would happen from the Rules that states one is to believe what is black white if the Church says so. In this case, even the ultimate authority, i.e. the Church, could not settle the issue, which suggests that Jesuits’ adherence to the probabilism has a higher authority than the Church does. Does such a scientific method as this, where the hierarchy of authority loses its final say even though it is based upon the supremacy of the authority, really work?

Peter Dear, Revolutionizing the Sciences: European Knowledge and Its Ambitions, 1500-1700 (NJ: Princeton University Press, 2001), 66. See also Malcolm Oster, Science in Europe, 1500-1800: A Secondary Sources Reader, 133, “[T]he thirteenth Rule of Loyola is explicit: ‘If we wish to be sure that we are right in all things, we should always be ready to accept this principle: I will believe that the white I see is black, if the hierarchical Church so defines it.’”

Malcolm Oster, Science in Europe, 1500-1800: A Secondary Sources Reader, 129-130.

Ibid., 132.

Alfredo Dinis, “Giovanni Battista Riccioli and the Science of His Time,” in Jesuit Science and the Republic of Letters, ed. Mordechai Feingold, 195-224 (USA: The MIT Press, 2003).

Ibid., 204.

See Dinis, 208, Riccioli says that “[s]o far, no proof based on celestial phenomena has been produced, which can demonstrate either the truth or the falsity of any of the hypotheses.”

Ibid., 204, “In any controversy in which reasons favoring opposite sides are of equal evidence, we should only choose that position which is favored by authority.”

Ibid., 205.