Galileo’s Theology of Science


How did modern people come to view science as independent of religion? It’s rather amazing that so many people could accept the apparent divergence of  science from their articles of faith, and that they could see as legitimate a political and legal system in which that was a possibility. Much of this can be traced back to the Galileo affair, which can deservedly be called the “Trial of the Millennium”. Galileo was the first to put into modern form the rationale for the autonomy of religion and science, something that grows more  important as science seems to be growing more revolutionary.

It was Galileo’s good fortune to be alive at the beginning of the Scientific Revolution, and thus to make great advances in astronomy even though he was primarily a mathematician and physicist. It was his bad fortune, however, to be dragged into yet another, far more politically charged field, that of theology. While it is true that “hindsight is 20/20”, there are a few aspects of the Galileo affair that tend to be unclear to the non-historian. For example, while most people see how the theory of evolution could contradict the Bible, it seems a bit much to claim that one can prove God to be a geocentrist. After all, we heliocentrists still say that the sun “comes up” or “goes down”, so what’s the big deal? The “big deal” concerns many aspects of the Modern Age that we take for granted. In this essay we shall focus on two these, the “autonomy of science” and a modern view of historical progress.

The “autonomy of science” really means the independence of any field or sphere of activity, such as politics, science, theology, art, economy, technology, et cetera. The classic example of this is the “separation of church and state” or, on another level, the independence of Faith and Reason. While it has always been the case that spiritual and temporal authority have been somewhat separate, it is distinctive of the modern age that this separation has grown ever more distant as time goes on. Prior to Galileo, faith and reason were held to be separate, but “Reason” was defined as the philosophy and science of St. Thomas Aquinas, far different from our modern progressive open-ended concept of reason.

In the final analysis, Galileo’s theological innovations can be boiled down to two principles of Biblical interpretation: First, that one must use scientific knowledge (natural reason) to interpret scripture:

“…though the Scripture cannot err, nevertheless some of its interpreters and expositors can sometimes err in various ways. One of these would be very serious and very frequent, namely to want to limit oneself always to the literal meaning of the words; for there would thus emerge not only various contradictions but also serious heresies and blasphemies, and it would be necessary to attribute to God feet, hands, and eyes, as well as bodily and human feelings like anger, regret, hate and sometimes even forgetfulness of things past and ignorance of future ones. Thus in scripture on finds many propositions which look different from the truth if one goes by the literal meaning of the words, but which are expressed in this manner to accommodate the incapacity of common people.” (Finochiaro pg. 49-50)


This principle dates back to St. Augustine, but has only recently become so important in modern times, as “non-overlapping magisterial”, or “NOMA”, for short.

NOMA radically claims that the Bible (and thus the Church?) had authority in matters concerning faith and morals, but not nature and science. Here is Galileo’s statement of NOMA:

“The authority of the Holy Writ has merely the aim of persuading men of those articles which are necessary for their salvation and surpass all human reason… I do not think it necessary to believe that the same God who has furnished us with senses, language, and intellect would want us to bypass their use and give us by other means the information we can obtain with them. This applies to those sciences about which one can read only very small phrases and scattered conclusions in the Scripture, as it is particularly the case for astronomy, of which it contains such a small portion that one does not find in it the names of all the planets; but if the first sacred writers had been thinking of persuading the people about the arrangement and the movements of the heavenly bodies, they would not have treated them so sparsely…(Ibid pg. 51-52)


In the 1600’s, NOMA would have been seen as an elaboration or radicalization of Aquinas’ doctrine of the separateness/ultimate agreement of Faith and Reason. Theists had long believed in the divine origin of nature and revelation, but Catholic theology was rather distinctive in including Reason as coming from God, meaning that radical fideism a la Tertullian (“I believe because it is absurd.”) is frowned upon. According to this teaching, if man was made “in the image of God”, then it seems likely that this refers to Reason. If this faculty of reason is in some way divine, then it is at least possible for it to share in God’s boundless knowledge of nature. Because of our mortal/sinful nature, our reason is incomplete without faith. The Christian humanism of Aquinas had convinced the church that there was no ultimate conflict between Reason and Faith, as Galileo explains thusly:

I think that no one will say that geometry, astronomy, music and medicine are treated more excellently in the sacred books than in Archimedes, Ptolemy, Boethius and Galen. So it seems that the royal preeminence belongs to it in the second sense, namely because of the eminence of the topic and because of the admirable teaching which could not be learned by men in any other way and which concerns chiefly the gaining of eternal bliss. … If all this is so, then officials and experts in theology should not arrogate to themselves the authority to issue decrees in the professions they neither exercise nor study; for this would be the same as if an absolute prince… being neither a physician nor an architect, wanted to direct medical treatment and the construction of buildings, resulting in serious dangers to the life of the unfortunate sick and the obvious collapse of structures. (Ibid pg. 100-101)


Galileo backs up his position with the authoritative St. Augustine’s On the Literal Interpretation of Genesis, which warns Christians not to give heathen scholars cause to disrespect Christianity by using scripture to defend falsity:

It is very scandalous … that any infidel should hear a Christian speak about these things [science] as if he were doing so in accordance with Christian Scripture… the distressing thing is not so much that an erring man should be laughed at, but that our authors should be thought by outsiders to believe such things, and should be criticized and rejected as ignorant, to the great detriment of those whose salvation we care about. For how can they believe our books in regard to the resurrection of the dead, the hope of eternal life and the kingdom of heaven, when they catch a Christian committing an error about something they know very well, when they declare things they have already been able to observe or to establish by unquestionable argument? (Quoted in Finochiario pg. 112)


One problem with NOMA in the modern age is that unlike classical thought, modern reason is always on the move, realizing its own limitations and transcending them. Originally NOMA was implemented by accepting Thomism as a stand-in for “reason”, but with the rise of modern science, “reason” is merely a place-holder for whatever results happen to be proven by researchers in the relevant fields of study.  If faith has to “respect” reason (as it must under NOMA) then it too must change in its interpretation and application. Furthermore, we can never have apodictic certainty as to when we have settled on the finally correct interpretation. This prolonged uncertainty is the bad side of progress, whose good side is emphasized by Galileo thusly: “Who wants to fix a limit for the human mind? Who wants to assert that every thing which is know able in the world is already known?” (Ibid pg. 51) This is a pretty modern sentiment for the age of witch trails, but progressivism is not utterly at odds with Christianity, especially if science can be marshaled “to the greater glory of God”, as it was during the Enlightenment.

To prohibit the entire science would be no different than to resist hundreds of statements of Holy Writ, which teach us how the glory and the greatness of the supreme God are marvelously seen in the open book of the heavens. Nor should anyone think that the reading of the very lofty words written on those pages is completed by merely seeing the sun and stars… on the contrary, those pages contain such profound mysteries and such sublime concepts that the vigils, labors, and studies of hundreds of the sharpest minds in uninterrupted investigation for thousands of years have not completely fathomed them. (Ibid pg. 103)

He then draws a parallel with the anatomical discoveries of Vesalius, who had recently proved classic authorities wrong empirically through dissection of human cadavers.

Even idiots realize that what their eyes see when they look at the external appearance of the body is insignificant in comparison to the admirable contrivances found in it by a competent and diligent philosopher anatomist when he investigates how many muscles, tendons, nerves and bones are used… (Ibid pg. 103)


Galileo hoped to create, in the minds of the authorities, an analogy between himself and Vesalius. Both improve on Aristotelian science though a combination of theoretical and practical knowledge as well as new methods of observation (dissection and the telescope) not available to the ancients.

For Galileo, the relation of faith and reason follows from his Christian/Platonic cosmology: “For the Holy Scripture and nature both equally derive from the divine Word, the former as the dictation of the Holy Spirit, the latter as the most obedient executrix of God’s commands…” (Ibid pg. 50)  This explicitly contrasts with the near-Manichean suspicion of nature implicit in much anti-witch ideology. It also helps to dispel the suspicion of science as secular and worldly in opposition to religion rather than its complement or supplement, as we see from this letter by Galileo:

…if I ask Froidmont whose works are the sun, the moon, the earth, the stars, their arrangement, and their motions, I think he will answer they are the works of God; and if I ask from whose inspiration Holy Scripture derives, I know he will answer that it comes from the Holy Spirit. Thus, if the world is the works, and the Scripture the words of the same God… Is it perhaps less noble and lofty to work than to speak? (Ibid pg. 224-225)


This statement is important for two reasons: first, it promotes action with respect to theory, something which essentially distinguishes modern from classical science. Second, it radically places astronomy in the category of divine knowledge and gives man access to the mind of God independent of revelation. While this greatly elevates the status of the scientist, it does not make him the equal of the priest.  According to Galileo, science can never reveal the purpose of the universe, only its behavior and usefulness in secular matters, but science completes faith by sharpening Biblical interpretation, by preventing the discredit of faith among the infidel, and by its revelation of the greater glory of God through his creation.

Though Galileo lost his immediate trial before the Inquisition, he has been elevated by history for his scientific work. However, it would also be fitting to memorialize his key role making science free and safe in a religious world. In 1893, Pope Leo XIII endorsed the view of science and faith first put forth by Galileo long before, an act which merely ratified a fait accompli. Science and faith had come to such an understanding such that by the time of Darwin, biologists had merely to follow the playbook set by Galileo centuries before.




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