International Catholic University


Galileo: Science and Religion

Galileo: Theologian

William E. Carroll

In the front of his own copy of the Dialogue Concerning the Two Chief World Systems, Galileo wrote the following:

Take care, theologians, that in wishing to make matters of faith of the propositions attendant on the motion and stillness of the Sun and the Earth, in time you probably risk the danger of condemning for heresy those who assert the Earth stands firm and the sun moves; in time, I say, when sensately or necessarily it will be demonstrated [col tempo, dico, quando sensatamente o necessariamente si fusse dimostrato] that the Earth moves and the Sun stands still.

This passage reveals many of themes crucial for understanding the controversy between Galileo and the Inquisition. We find in it both Galileo's commitment to demonstrations in science and his admission that there is not yet such a demonstration for the motion of the Earth. The passage also reaffirms a key principle Galileo set forth in the "Letter to the Grand Duchess Christina": that when investigating physical questions one should not begin with biblical texts. Galileo warns the theologians to avoid acting imprudently, lest they be faced with the unpleasant task of condemning as heretical those propositions which they now declare to be orthodox.

Such diverse commentators on Galileo as Giorgio di Santillana, author of The Crime of Galileo, and Pope John Paul II have praised the astuteness of Galileo's theological observations on the relationship between science and scripture. In ceremonies commemorating the 100th anniversary of the birth of Einstein in 1979, and again in October 1992, the Pope, referring to the fundamental compatibility between science and the Bible, quoted approvingly from Galileo's "Letter to the Grand Duchess Christina," in which Galileo observed that God is author of all truth, both the truth of nature and the truth of Scripture. di Santillana's praise of Galileo's theology is effusive: "[Galileo] warns and exhorts with the dignity of a [Church] Father of the early centuries...." and "The content of his spurned and incriminated theological letters has become official Church doctrine." di Santillana laments that there was no "young Aquinas" in Rome in 1616 to follow Galileo's lead in theology. A more circumspect scholar such as Owen Gingerich, professor of the history of astronomy at Harvard, writes recently that the Catholic Church should now accept "Galileo's arguments about the reconciliation of science and scripture." Gingerich acknowledges that the theological principles enunciated by Galileo have "long since" been adopted by Protestant and Catholic theologians, but he still thinks it would be useful for the Catholic Church to make an official pronouncement confirming Galileo's theological arguments.

Even in the recent work of Mauro Pesce of the University of Bologna, who has written extensively on Galileo's principles of biblical exegesis, we find the claim that Galileo represents a missed opportunity for the Church in the seventeenth century to discover an adequate relationship between modernity and religion. According to Pesce, it was not until Pope Leo XIII's encyclical, Providentissimus Deus, in 1893, that the Church would accept, even in an attenuated form, the principles enunciated by Galileo. Thus, between February 1616, when the theologians of the Inquisition condemned Copernican astronomy, until 1893, there was a continual official refusal to accept Galileo's proposals for the compatibility between religion and science. According to Pesce, the fundamental issue from 1616 to 1893 was not really the acceptance of Copernican astronomy, but rather the unwillingness to accept the hermeneutical principle that the truth of Scripture is religious and not scientific. Pesce claims that it was this distinction between science and religion which constituted the core of Galileo's claims in his letters between 1613 and 1615, and, furthermore, that it was the rejection of this principle which lies behind the condemnation of Copernicus. Galileo, in such a view, has become an icon for modern culture, and thus this final lecture returns to the themes I set forth in my initial lecture on the legend of Galileo.

In this lecture I want to examine in some detail Galileo's theological arguments concerning the relationship between science and Scripture, as they are found in a series of four letters and related notes he writes from 1613 to 1615: letters to Benedetto Castelli, Piero Dini, and the Grand Duchess Christina of Tuscany. Galileo writes these letters in response to an increasing campaign waged by academic and theological opponents: priests and professors who were convinced that Copernican astronomy and its apparent implications for Aristotelian physics, cosmology, and metaphysics, presented a serious threat to the traditional interpretation of the Bible, as well as to the whole edifice of Catholic theology. Despite these wider implications for the relationship between Aristotelian thought and Christian faith, the debate which raged in the second decade of the 17th century had as its focus the Bible and the compatibility of the new astronomy with certain passages in the Bible. The debate took on a special urgency in that, in the previous century, the Council of Trent, in response to the challenges of Protestant thinkers, had forbidden Catholics to interpret the Bible contrary to the sense of the sacred text which "the Church . . . has held and holds . . . or contrary to the unanimous teachings of the Fathers. . . ." As I pointed out in a previous lecture, Cardinal Roberto Bellarmino reminded Galileo of precisely this point when he wrote to him in April 1615: "And if [you] . . . . would read not only their works [the works of the Church Fathers] but the commentaries of modern writers . . . you would find that all agree in expounding literally that the sun is in the heavens and remains motionless in the center of the world. Now consider in all prudence," Bellarmino continues, "whether the Church could support the giving to Scripture of a sense contrary to the holy Fathers and all the Greek and Latin expositors."

The Cardinal was well aware that the injunction of the Council of Trent referred to the interpretation of Scripture concerning matters of faith and morals. But Bellarmino reminded Galileo that one could not simply say that the new astronomy was not a matter of faith and morals and thus exempt from the strictures of the decree of Trent: for even if not a matter of faith with respect to its subject [ex parte obiecti], it was, he noted, a matter of faith in that God is the unerring author of all of Scripture [ex parte dicentis], including those passages which describe astronomical phenomena. Thus one could not deny what texts from Psalms and the Book of Joshua said about the immobility of the earth and the mobility of the sun because in doing so one would challenge the divine authorship of the Bible.

Nevertheless, Bellarmino was willing to reject the traditional reading of the Bible "if there were a true demonstration that the sun was in the center of the universe .... and that the sun did not go around the earth but the earth went around the sun." If there were such a scientific demonstration, Bellarmino admitted that it would then "be necessary to use careful consideration in explaining the Scriptures that seemed contrary, and we should rather have to say that we do not understand them than to say that something is false which has been proven."

Galileo was well aware of the concerns enunciated by Cardinal Bellarmino. Nearly two years before, in a brief letter to Benedetto Castelli, his protege and professor of mathematics at the University of Pisa, Galileo sketched in outline what would become the full-blown treatise ostensibly addressed to Christina, Grand Duchess of Tuscany. Since 1610, when Galileo first published the results of his astronomical observations and began his long, public defense of Copernican astronomy he had to counter the arguments of those who appealed to the Bible to defend traditional geocentric cosmology. Galileo was chief mathematician and philosopher in the Medici court in Florence and in the letter to the Grand Duchess, penned after Bellarmino sent his letter in April 1615, we find Galileo's response to the arguments advanced by his opponents. We have already examined the basic elements of the letter, but it is worth reiterating the two general principles Galileo sets forth:

1. There can be no contradiction between the truths of science and the truths of faith. God is the author of all truth: both the truth known through revelation and the truth known through reason alone. This is hardly a revolutionary position for a Catholic to maintain. Augustine and Aquinas admit as much, as did Cardinal Bellarmino. Remember, the Cardinal observed that were there to be a demonstration that the Earth moved, then the Church could not maintain that the Bible revealed the opposite. Indeed, Cardinal Bellarmino and Galileo shared the same Aristotelian understanding of what a demonstration in science is. Science for them was necessary knowledge in terms of causes.

2. The purpose of God's revelation in Scripture is not to teach men about natural philosophy but to lead them to salvation. In the words of Cardinal Baronius, quoted approvingly by Galileo: "the Bible teaches us how to go to heaven, not how the heavens go." Although Galileo does emphasize more than do his contemporaries the distinction between the essentially religious purpose of the Bible and other truths which it may contain, he does not really anticipate a radical separation between religious and other truths in the Bible. As we examine this question more fully, we will see that there is less of a difference between Galileo and the theologians of the Inquisition than is generally thought.

When Gingerich, di Santillana, and the Pope refer to Galileo's insights on the relationship between science and Scripture, these are the two principles to which they refer. What so many see as particularly modern in Galileo's understanding of the relationship between the Bible and science is but the reaffirmation of traditional Catholic thinking, easily seen in the writings of Augustine and Aquinas. Mauro Pesce claims, in addition, that Galileo goes further than either Augustine or Aquinas in that he makes an epistemological claim in distinguishing science from religion (the Book of Nature is read more easily than the Book of Scripture), and, furthermore, that Galileo, at least implicitly, lays the groundwork for a modern conception of religion. Pesce, as well as many others, see the letter to the Grand Duchess as one of the charter documents of the modern world: a call for the emancipation of scientific reflection from the forces of traditional religion and ecclesiastical authority.

Galileo, however, was not content to reaffirm traditional Catholic principles. He sought to use these principles to urge the Church not to condemn Copernican astronomy. Yet, it is important to recognize that the principles he employed were shared by the theologians of the Inquisition.

Even if one admits that the purpose of the Bible is not to teach scientific truths, still the question remains: does the Bible have any authority at all in evaluating questions in the natural sciences? To grant that the purpose of the Bible is to lead human beings to salvation does not mean that the Bible has nothing to say about the world of nature. Galileo address this subject in the following way. He affirms that the Bible cannot err, but quickly adds that the inerrancy of the Bible concerns its true meaning [il suo vero sentimento] and not what what "its bare words" may signify [che suona il puro significato delle parole]. A slavish adherence to the "unadorned grammatical meaning" [nel nudo suono literale] of any particular passage may lead to follies, error, and heresy. One may come to think, for example, that God has hands, feet, eyes, that He gets angry and is subject to other emotions. The Bible often contains passages written in a mode "to accommodate" these passages to "the capacities of the common people” [per accomodarsi all capacita del vulgo].

Too many translators of these texts miss an important distinction. When Galileo refers to "il nudo" or "il puro" "significato delle parole," "il nudo suono litterale," or similar phrases, he does not mean the literal sense of scripture. As Aquinas and others had observed, the literal sense of the Bible, which is always true, is what the Author, ultimately God, intends the words to mean. Galileo, observing this same distinction between what we might call a literal and a literalistic reading of the Bible, distinguishes between a naive literalism and "il vero sentimento" (the true meaning) of the text. The literal sense is not the same as what the bare words signify. Galileo, thus, is embracing, not challenging, a traditional Catholic principle of biblical exegesis.

Cardinal Bellarmino was well aware of the difficulties in discovering the truths in Scripture. Every sentence in the Bible has a literal or historical meaning, i.e., "the meaning which the words immediately present." The literal meaning is either simple, "which consists of the proper meaning of the words," or figurative, "in which words are transferred from their natural signification to another." When the Bible refers to "the right hand of God," the simple literal sense would mean a part of God's body; whereas the figurative literal sense means God's power. Since, if we were to read the passage according to the simple literal sense there would be an absurd attribution of a body to God, a figurative sense must be the true meaning of this passage. There are as many different types of figurative meaning as there are types of literary figures, but all these figurative meanings are the literal sense of Scripture.

On the basis of such distinctions -- and notice that the examples Galileo uses concern passages in the Bible which attribute certain human attributes to God, and with which obviously Bellarmino would agree -- Galileo, with rhetorical deftness advances a wider argument:

Hence I think that I may reasonably conclude that whenever the Bible has occasion to speak of any physical conclusion [alcune conclusione naturale] (especially those which are very abstruse and hard to understand), the rule has been observed of avoiding confusion in the minds of the common people which would render them contumacious toward the higher mysteries. . . . Who, then, would positively declare that this principle [of accommodation] has been set aside, and the Bible has confined itself rigorously to the bare and restricted sense of its words [i puri ristretti significati delle parole], when speaking but casually of the earth, of water, of the sun, or of any other created thing? Especially in view of the fact that these things in no way concern the primary purpose of the sacred writings, which is the service of God and the salvation of souls. . . .

This being granted, I think that in discussions of physical problems [problemi naturali] we ought to begin not from the authority of scriptural passages [non si dovrebbe cominciare dalle autorità di luoghi scritture], but from sense experience and necessary demonstrations [ma alle sensato esperienze e dalle dimostrate necessarie]; for the Holy Bible and the phenomena of nature proceed alike from the divine Word, the former as the dictate of the Holy Ghost and the latter as the obedient executrix of God's commands. It is necessary for the Bible, in order to be accommodated to the understanding of every man [per accomodarsi all'intendimento dell'universale], to speak many things which appear to differ from the absolute truth [dal vero assoluto] so far as the bare meaning of the words [al nudo significato delle parole] is concerned.

If we compare these passages in the letter to the Grand Duchess with the same or similar passages in the 1613 letter to Castelli, we discover some interesting differences. Although many passages from the 1613 letter appear verbatim in the 1615 letter to the Grand Duchess -- still the 1615 letter is greatly expanded. In 1613, Galileo writes to Castelli using almost the same words he will employ in 1615, save for the observation that: "in physical disputes [disputi naturali] it [the Bible] should be reserved to the last place [ella doverebbe esser riserbata nell'ultimo luogho]." In 1615, in the passage quoted above, Galileo argues that "we ought not to begin from the authority of scriptural passages." This change -- from reserving the Bible to last place in discussing scientific questions to the admonition not to begin from the authority of scripture -- is indicative of the rhetorical thrust of the Letter to the Grand Duchess. For the real audience Galileo addresses is not the Grand Duchess, but theologians and Church officials in Rome. He hoped to prevent the Inquisition from condemning Copernican astronomy.

There is another change between the 1613 letter and the 1615 letter which indicates Galileo's awareness of a subtle theological distinction. In explaining that the purpose of the Bible is to lead men to salvation and not to disclose information extraneous to that purpose, Galileo writes the following to Castelli in 1613:

I would believe [Io crederei] that the authority of Holy Writ had only the aim of persuading [l'autorità delle Sacre Lettere avesse avuto solamente la mira a persuadere] men of those articles and propositions which, being necessary for salvation [sendo necessarie per la salute loro] and overriding all human reason [superando ogni umano discorso], could not be made credible by another science, or by other means than the mouth of the Holy Ghost itself.

In the letter of 1615, Galileo alters this passage; he writes:

I should judge that the authority of the Bible had the aim principally of persuading [l'autorità delle Sacre Lettere avesse avuto la mira a persuadere principalmente] men of those articles and propositions which, surpassing all human reasoning, could not be made credible by another science, or by any other means than through the mouth of the Holy Ghost.

In 1613, Galileo wrote that the purpose of the Bible was only [solamente] to persuade men of those truths which surpassed human reason. In 1615, he changes the adverb to "principally" [principalmente]; thereby, he does not exclude from the purpose of the Bible the revelation of truths which are within the realm of human reason. Notice, also, that the 1615 text omits the phrase "being necessary for salvation;" thus, Galileo eliminates a restriction concerning the subject of the articles and propositions which come under the "authority of the Bible." I think that these changes are significant for two reasons. First, with Aquinas, Galileo could now allow that some truths about God and man necessary for salvation which can be known by reason are also revealed in Scripture. Second, he admits that there may be truths in the Bible which are not directly connected to the Bible's purpose of leading human beings to salvation. Galileo is skilled in rhetoric. In order to persuade the Church not to act precipitously and condemn Copernican astronomy, Galileo, as we have seen, often makes it appear as though the new astronomy has already been demonstrated to be true. The Letter to the Grand Duchess is richly laced with quotations from the Church Fathers, principally Augustine, all left in Latin: passages which lend authority to his arguments. The passages quoted reinforce the general principles of the complementarity of science and scripture, and the need to avoid naive, literalistic interpretations of the sacred text.

In the absence of a scientific demonstration for the motion of the earth, Cardinal Bellarmino urged prudence: do not challenge the traditional readings of those biblical passages which have been interpreted as affirming the immobility of the earth. The Cardinal was acutely aware of Protestant challenges to the Catholic Church's claim to be the sole, legitimate interpreter of God's word. In fact, as I suggested in a previous lecture, it seems that Bellarmino was more concerned with maintaining the authority of the Church to be the authentic interpreter of Scripture than he was in refining principles of biblical exegesis. Nevertheless, on the level of the principles concerning the relationship between science and scripture, Cardinal Bellarmino and Galileo were in agreement, just as they were in agreement concerning the Aristotelian requirements for scientific knowledge.

Yet, there is something more in Galileo's arguments, more than the traditional affirmation that God is the author of the book of nature and the book of scripture and that the truths of nature and the truths of scripture cannot really be in conflict. In the passage in the 1615 Letter to the Grand Duchess which we have been examining, and elsewhere in the letter, we find an additional argument, an argument not found in his earlier letters on the subject. Let me quote three such passages in which Galileo argues for the role of science in discovering the true sense of those scriptural texts which address scientific questions.

...[Having become certain of any physical conclusions [venuti in certezza di alcune conclusioni naturali], we ought to utilize these as the most appropriate aids in the true exposition [alla vera esposizione] of the Bible and in the investigation of those meanings which are necessarily contained therein [quei sensi che in loro necessariamente si contengono], for these [meanings] must be concordant [concordi] with demonstrated truths [le verità dimostrate].

[Since] two truths cannot contradict one another [due verità non possono contrariarsi]. . . it is the function of wise expositors [of Scripture] to seek out the true senses [i veri sensi] of scriptural texts. These will unquestionably accord [indubitabilmente saranno concordanti] with the physical conclusions [conclusioni naturali] of which we are already certain and sure [certi e sicuri] through manifest sense or necessary demonstrations [senso manifesto o le dimostrazioni necessarie].

When one is in possession of knowledge about questions of nature which are not matters of faith, based on indubitable demonstrations or sensory experience, since such knowledge is also a gift from God, one must apply it to the investigation of the true meanings [veri sensi] of Scripture in those places which apparently seem to read differently. These senses would unquestionably be discovered by wise theologians [indubitatamente saranno penetrati da' sapienti teologi], together with the reasons for which the Holy Ghost sometimes wished to veil itself under words with a different meaning [velare sotto parole di significato diverso].

Galileo argues that there is not simply a complementarity between the Bible and science, in that the truth of one cannot contradict the truth of the other, but that there also must be a concordance between science and those passages in the Bible which appear to make claims about the physical nature of the universe.

There is a certain oscillation, or, perhaps, tension between Galileo's insistence that the Bible is extraneous to the natural sciences and his insistence that the Bible reflects the conclusions of the natural sciences. Galileo's principles were shared by his opponents in the Inquisition, although they reached a different conclusion when they examined the particular case of Copernican astronomy. The theological consultants of the Inquisition were asked to evaluate the claims of Copernican astronomy. They issued their report to the cardinals of the Inquisition in February 1616. As I discussed in a previous lecture, the report of the consultants concluded that the claim that the sun was immobile and at the center of the universe was "foolish and absurd in philosophy, and formally heretical since it explicitly contradicts in many places the sense of Holy Scripture, according to the literal meaning of the words and according to the common interpretation and understanding of the Holy Fathers and the doctors of theology." The theologians also concluded that the claim that the earth moves was foolish and absurd in philosophy and, "in regard to theological truth it is at least erroneous in faith." Many transcriptions of the report of the theological consultants fail to place a comma after the word "philosophia." The original Vatican manuscript (folio 42r) has a semicolon after "philosophia" and the late nineteenth century edition of the collected works of Galileo (19: 321) has a comma. Most translations into English omit the punctuation. Such a transcription, without a comma, "conveys the impression" that contradicting the Bible "is being given as a reason for ascribing both philosophical-scientific and theological heresy." But the comma between "philosophia" and "et" separates the claim of theological heresy from the claim of philosophical and scientific error. The distinction is crucial! For the original manuscript shows us that the theologians first conclude that the proposition is false and absurd philosophically and then conclude that it is heretical because it contradicts the Bible.

I want to point out, first, that these conclusions are conclusions of a committee of experts; they are not the official teaching of the Church. Even though the Inquisition, in dealing with Galileo, operated on the basis of this report, the report remains a committee report; it is not an official act of the Church. Too often historians of the Galileo affair fail to distinguish between such committee reports and formal decisions of the Church. And, as I suggested in my previous lectures, some scholars fail as well to distinguish between disciplinary and doctrinal decisions. It is important to note that the first part of each of the two conclusions reached by the theologians is that Copernican astronomy "is false and absurd" philosophically. Why should the theological experts of the Inquisition care whether Copernican astronomy is false scientifically? First of all, there is the ancient Catholic commitment to the safeguarding of reason since, as Aquinas would say, reason is a way to God. Aquinas, himself, will refer to those propositions about God, such as that He exists, which serve as preambles to faith. More importantly for our purposes, I think, is that these theologians were committed to the complementarity between science and scripture. If a proffered scientific proposition is false, scripture certainly cannot be in agreement with it, since the Bible cannot affirm as true that which reason knows to be false. Furthermore, in reaching the conclusion that Copernican astronomy contradicts the Bible, the theologians accepted as incontrovertibly true a particular geocentric cosmology, and, on the basis of such an acceptance, they insisted that the Bible be read in a certain way. Thus, in part, they subordinated scriptural interpretation to a physical theory. They proceeded in this manner because, like Galileo, they were convinced that the Bible contained scientific truths and that, on the basis of what is known to be true in the natural sciences, one could discover the same truth in related biblical passages.

Allow me to conclude this brief account with a broader historical claim. As William Wallace, A.C. Crombie, and others have shown, Galileo's scientific achievements must be recognized in the setting of a progressive Aristotelian science; that is, Galileo's arguments in physics, including his refutation of Aristotelian conclusions about the immobility of the earth, proceed from first principles of Aristotelian natural philosophy. Similarly, Galileo's theological claims are part of the traditional heritage of Catholicism, and, further, they are a part of the theological environment of the Counter Reformation Church. The Council of Trent's injunctions concerning the proper reading of Scripture are recognized by both Galileo and the Inquisition. Let us recall, further, that a crucial feature of the disputes of the Reformation was the calling into question by the Reformers of the very criterion of truth by which one resolves theological questions. In other words, the Reformation was not simply a debate about grace, free will, predestination, and the like, but it also involved a debate about the Catholic Church's claim to be the authentic judge of such disputes.

Although Protestants and Catholics would disagree about the role of the Church as a criterion of truth, they could, however, and they did, appeal to a common text, the Bible: a text, which, in a sense, standing alone, served as the only common ground from which to argue. Both sides, thus, were encouraged to find in the Bible evidence for their respective theological conclusions. The Bible, therefore, came to be treated as a reservoir of conflicting theological propositions. Thus, we find a tendency on the part of both Protestants and Catholics to treat the Bible as a theological text book: a compendium of syllogisms or dogmatic propositions. One of the obvious dangers in viewing the Bible as a text book in theology is a literalistic reading of the text: a literalism all too apparent in the Inquisition's reaction to the perceived threat of the new astronomy. Do we not see a similar tendency in Galileo's insistence that we can discover scientific propositions in the Bible? Armed with scientific demonstrations we, or at least wise expositors, possess the key to discover those scientific propositions which are contained in the Bible. Despite the commonly accepted view of most scholars, Galileo's principles of biblical interpretation do not anticipate a modern distinction between science and an essentially religious reading of the Bible. Galileo the theologian reaffirms not only the ancient traditions of Catholic theology, but manifests as well theological tendencies in some sense peculiar to his age.

For a fuller treatment of the theme of this lecture, see: William E. Carroll, "Galileo and the Interpretation of the Bible," Science & Education 8:2 (1999), pp. 151-187.

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