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At the Roots of the 1616 Decree: Robert Bellarmine’s Letter to Paolo Foscarini

by Luca Arcangeli

In the same year in which Galileo Galilei (1564-1642) composed the letter to Madame Christina of Lorraine, a Carmelitan father, Paolo Antonio Foscarini (1565-1616), gave the press in Naples a book entitled “Letter on the Opinion of Pythagoreans and of Copernicus about the Movement of the Earth and the Stability of the Sun.”[1] For the first time a man belonging to the gerarchy of the Church (he was in fact the provincial of the Carmelites of Calabria) officially exposed himself to criticism by the explicit adherence to the Copernican belief, searching for both an exegetic and a philosophical justification of it.

On March 21, 1615 Giovanni Ciampoli (1589-1643) [2] wrote a letter to Galileo full of concern, warning him of the possible repercussions of Foscarini’s publication [3]. In fact, the work had been put under scrutiny by the Roman Inquisition, and an anonymous theologian had written a note underlining the aspects of it to be censured [4]. Foscarini, who found himself in Rome and who was probably warned by Ciampoli himself [5], promptly wrote a short letter addressed to Cardinal Bellarmine (1542-1621) [6]. In this letter Foscarini tried to fill a major gap in his writing: the lack of citations from the Fathers of the Church and from reflections by authoritative theologians, aspects characteristic instead of the letter to Madame Christina of Lorraine. In addition to classic references to De Genesi ad litteram by Augustine, which abound in the Galilean letter, Foscarini also cites in his letter to Bellarmine De locis theologicis by Melchior Cano and the commentaries on Genesis by Benedetto Pereira and by Cardinal Caietano. The Cardinal did not delay in responding, and on April 12, 1615 he addressed a short epistle, of only three paragraphs, to the Carmelite.

Advisor to the Roman Inquisition starting in 1597, Robert Bellarmine (1542-1621) was one of the top authorities on the theology of the time and the undisputed champion of controversial theology, dedicated to apologetics of the Catholic faith against the errors of protestantism. In his career he confronted the most heated disputes: the relationship between papal and royal powers, the problem of Grace in Molinism, and Giordano Bruno’s trial. Finally, as we see, he also entered, already elderly, into the Copernican dispute.

Compared to the writings of Foscarini and Galileo, Cardinal Bellarmine’s letter stands out for its extreme conciseness. After the usual initial pleasantries, the Cardinal immediately tackles the problem, defining how the Copernican proposal should be interpreted:

«First I say that it seems to me that your Paternity and Mr. Galileo are proceeding prudently by limiting yourselves to speaking suppositionally and not absolutely, as I have always believed that Copernicus spoke». [7]

We note that the letter, although addressed to Foscarini, also explicitly mentions Galileo, thereby directing to both a single response. But what does it mean to speak suppositionally? In the first place, it meant maintaining Copernicanism as hypothetical until proved irrefutably [8], and at the end this was in agreement with the understanding of the astronomy of the time, considered part of mathematics and therefore subject to different representations to justify the same phenomenon. In the second place, however, Bellarmine’s warning meant that one should not have had any realistic claim in arriving at the physical description of the celestial bodies by proposing the Copernican model of the universe. This could have been viewed as less acceptable to scholars of a science that had begun precisely to emancipate itself from mathematics. When De revolutionibus by Copernicus (1473-1543) was published in May of 1543, it used a text of the protestant theologian Andreas Osiander as an introduction, in which he explained that heliocentrism was a proposal of an astronomical model to facilitate the calculations of celestial motions, but he did not want to draw any realistic conclusions in the field of natural philosophy. In Bellarmine’s letter, the distinction is clear between the astronomer-mathematician who does calculations on one side and, on the other side, the natural philospher who qualitatively describes the real in light of a theologically inspired metaphysics:

«However, it is different to want to affirm that in reality the sun is at the center of the universe and only turns on itself, without moving from east to west, and the earth is in the third heaven and revolves with great speed around the sun; this is a very dangerous thing, likely not only to irritate all scholastic philosophers and theologians, but also to harm the Holy Faith by rendering Holy Scripture false». [9]

The intellectual effort of Galileo was instead aimed at overcoming the divorce between the mathematical calculation of phenomena and their descriptions in terms of qualitative causes; the Galilean methodology was based on repeated experimental observation, on the explication of regularities present in nature and on their rigorous formulation in terms of the mathematical-geometric language. This was for Galileo the true and proper natural philosophy, the only one that could claim the possibility of realistic and verifiable assertions. The ancient science of being in the Aristotelian model, which served as the substrate for the descriptions in traditional natural philosphy, was substituted by Galileo with mathematics. The minimum of metaphysics still useful was needed for the justification of the intelligibility of the universe:

«Philosophy is written in this grand book, the universe, which stands continually open to our gaze. But the book cannot be understood unless one first learns to comprehend the language and read the letters in which it is composed. It is written in the language of mathematics, and its characters are triangles, circles and others geometric figures without which it is humanly impossible to understand a single word of it; without these, one wanders about in a dark labyrinth». [10]

If the world is written in mathematical language, then this is the guarantee of its legibility and of the realism of our assertions about it; far from being just a means to calculate the celestial motions, the Copernican model is therefore a truthful description of the structure of the universe. In Aristotelian thought instead, mathematics, as abstraction from mutation, could not provide the knowledge of the cause of observed events but only describe their mathematical aspects. In Aristotelian natural philosophy mathematics alone could never provide an adequate definition of the substance that was the cause of the change, precisely because it only considered its mathematical attributes: it was not legitimate to reduce qualitative differences such as between an upward, downward, or circular motion to simple geometric differences. [11]

Thus, we see an “epistemological fracture” at work between the natural philosophy of Galileo and the traditional one of his time, shared by Bellarmine as well as by Foscarini, who, for as much as he was Copernican, was equal to his opponents in his scientific methodology. The fundamental question was: what degree of truth should be attributed to the Copernican proposal? Bellarmine proposed a truth purely conventional, Galileo and Foscarini a realistic truth. But how could one justify the realism of it? Foscarini proposed, on a traditional basis, a revision of some metaphysical principles and a rereading of the Bible to replace geocentrism with heliocentrism, keeping the rest unaltered. More radically, Galileo wanted a reform in the way of practicing natural philosophy, disconnecting it from metaphysical reflections and basing it on the verifiability of experiments and on the rigor of the mathematical language: the acceptance of heliocentrism was only a consequence of a greater change that involved the revision of the overall system of knowledge.

The conventionalist strategy that Bellarmine proposed to Foscarini and Galileo was the simpler way out of the impasse, allowing astronomers to proclaim themselves Copernican while remaining in line with tradition and without initiating a reform of knowledge that would have proved complex and dangerous. The epistemological reform in this context seems to go hand in hand with the political: maybe it is no coincidence that Galileo requested his patrons, the Medicis, to name him besides mathematician also philospher of the court and that Bellarmine highlights among the risks that of irritating philosophers and scholastic theologians. Here the impression is that one is not speaking only about theories but about persons with interests to defend.

Bellarmine cites in conclusion the most formidable opponent to Copernicanism, namely its contradiction from the biblical text:

«I say that, as you know, the Council [of Trent] prohibits interpreting Scripture against the common consensus of the Holy Fathers; and if Your Paternity wants to read not only the Holy Fathers, but also the modern commentaries on Genesis, the Psalms, Ecclesiastes, and Joshua, you will find all agreeing on the literal interpretation that the sun is in heaven and turns around the earth with great speed, and that the earth is very far from heaven and sits motionless at the center of the world. Consider now, with your sense of prudence, whether the church can tolerate giving Scripture a meaning contrary to the Holy Fathers and to all the Greek and Latin commentators. Nor can one answer that this is not a matter of faith, since it is not a matter of faith “as regards the topic”, it is a matter of faith “as regards the speaker». [12]

To accept the heliocentric theory puts us in a very awkward place with the biblical wording, which in many passages seems to affirm, to the letter, the contrary. As much as Galileo and Foscarini try to find a basis in the tradition of the Fathers and the exegetes, Cardinal Bellarmine emphasizes that

the literal interpretation of the geocentric passages dominates in the history of the Church and therefore should be followed. Already Session IV of the Council of Trent had strongly affirmed the crucial role of Tradition and the ecclesiastical institution in determining the correct meaning of the Scriptures against Protestant deviations: to carry out a Copernican rereading of the Bible going against a consolidated view was, at the very least, imprudent.

Having clarified this, the Cardinal challenges – in two lines – the principle of adaptation of which both Foscarini and Galileo had made much use: we cannot affirm that the question of the structure of the universe is not a matter of faith and declassify the verses that speak of it in adaptation strategies for the understanding of the common people. If, strictly speaking, it is true that cosmology is not a matter of faith, it is likewise true that since the Bible speaks of it, it falls anyway within its horizon of authority. Here Bellarmine resumes one of his exegetical arguments, already contained in his monumental work Disputationes de Controversiis, according to which there are many things in the Scriptures that in themselves do not involve faith, that is, it is not necessary to believe in them for Salvation, but it is nevertheless necessary to believe in them simply for the fact that they are written. [13]

While on the one side Galileo and Foscarini had used the adaptation principle to limit the scope of application of the authority of sacred text, on the other Bellarmine uses his principle of literal fidelity to the Bible exactly to erode these limits and protect the full authority of the statements contained in it. [14]

Bellarmine’s letter closes with a kind of openness to the possibility of the opposing argument:

«I say that if there were a true demonstration that the sun is at the center of the world and the earth in the third heaven, and that the sun does not circle the earth but the earth circles the sun, then one would have to proceed with great care in explaining the Scriptures that appear contrary; and say rather that we do not understand them than that what is demonstrated is false. But I will not believe that there is such a demonstration, until it is shown me». [15]

Cardinal Bellarmine thus grants the possibility of there being a demonstration of the truth of heliocentrism; at which point, however, rather than reconstruct a biblical cosmology on a Copernican basis as Foscarini did, it is good to withhold judgment and refrain from trying to immediately reinterpret the verses in the Copernican sense or through the lens of the adaptation principle. The profound respect Bellarmine had for Sacred Scripture emerges again, with stretches of fidelity to the purely literal datum, where the only guide for the correct interpretation was the Church and its Tradition, not the transient views of natural philosophy.

Bellarmine also emphasizes that heliocentrism was not a hypothesis sufficiently corroborated; in addition to the Ptolemaic and Copernican system, the semi-heliocentric model of Tycho Brahe (1546-1601) was also proposed. None of the three models was yet able to prevail with evidence relating to physical phenomena, and all permitted the calculation of planetary motion in a satisfactory way. Conscious of this, Galileo tried to identify in the phenomenon of the tides the definitive evidence for the acceptance of heliocentrism – evidence that we know today is not consistent – but without success. In this context, the suspension of judgment was the most scientifically reasonable attitude; on the other hand, what Galileo asked in the letter to Madame Christina of Lorraine was at least to not close the issue by virtue of a scriptural preconception. At the beginning of his letter Cardinal Bellarmine had placed a very clear either-or to his interlocutors: should the question of the truth of Copernicanism be put on the plane of convention or indisputable reality? Galilean natural philosophy did not fit either of these two planes: on one hand, conventionalism would have reduced it to the mere production of theoretical mathematical models, sterilizing any bond with experimental investigation; on the other hand, claiming to rise to unquestionable truths would have fatally drawn Galilean philosophy into metaphysical disputes, distancing it once again from experimental practice. Galileo limited himself to making explicit the minimum of metaphysics that could be needed to justify a realistic reference to mathematical physics: it interested him more to speak in terms of natural philosophy than to clarify its foundations.

In synthesis, there are two theoretical issues underlying the debate on Copernicanism: the foundations of the natural sciences and the historicity of biblical text. Though it is always a risky undertaking to speak about history in hindsight, we can nevertheless say that both fronts were lacking on both theoretical issues: both a historical awareness of the exegesis of the sacred text and a reflection on the limits and cognitive ability of the natural sciences were missing in the debate of the time, and their appearance took place in a horizon that lies beyond the analyzed events. These two theoretical issues, in addition to political, sociological and ecclesial causes, can explain why the Roman Inquisition came to promulgate the famous anti-Copernican decree of 1616.

Read the full text of Card. Bellarmino's Letter to Foscarini (1615, April 12)


1 P.A. FOSCARINI, Lettera del R.P.M. Paolo Antonio Foscarini carmelitano. Sopra l'opinione de' Pittagorici, e del Copernico. Della mobilità della terra, e stabilità del sole, e del nuovo pittagorico sistema del mondo, Napoli 1615. The text of the 1615 Napoletan edition of the letter is publically available on Google books. 

2 Humanist and priest, Giovanni Ciampoli was the ally of Galileo and the Medicis within the Roman Curia. Later he had a decisive role in the publication of Dialogo sopra i due massimi sistemi in 1632. 

3 G. GALILEI, Edizione Nazionale delle Opere, edited by A. Favaro, Giunti-Barbera, Firenze 1968, vol. XII, 160. 

4 Cf. P. PONZIO, Copernicanesimo e Teologia, scrittura e natura in Campanella, Galilei e Foscarini, Levante Editori, Bari 1998, 87. 

5 We have a letter to Galileo dated March 28, 1615, in which Ciampoli informs him that he had met Foscarini in person, who called himself an affectionate admirer of the scientist. On this occasion it is probable that Foscarini was alerted to the actions of the Roman Inquisition. 

6 Cf. PONZIO, Copernicanesimo e Teologia, 88. 

7 GALILEI, Edizione Nazionale delle Opere, vol. XII, 171. 

8 Cf. R.J. BLACKWELL, Galileo, Bellarmine, and the Bible, University of Notre Dame Press, Notre Dame 1991, 85. 

9 GALILEI, Edizione Nazionale delle Opere, vol. XII, 171. 

10 Ibidem, vol. VI, 232.

11 Cf. A.C. CROMBIE, Da Sant’Agostino a Galileo, Feltrinelli, Milano 1982, 55. 

12 GALILEI, Edizione Nazionale delle Opere, vol. XII, 172.

13 R. BELLARMINO, Disputationes de Controversiis, I,I,4,12.

14 This battle on the application or not of the authority of the Holy Bible closely recalls the debate, just as heated at the time, on the authority of the Pope, contained in the fourth book of Disputaniones by Bellarmine entitled “De summo pontefice”. Here Bellarmine theorized the concept of potestas indirecta to justify the possibility of the pope’s power, although not being ipso facto an earthly ruler, to concern himself, however, with the political situation if the spiritual salvation of Christians was at stake. In the first as in the second case Bellarmine was trying to protect the authority of the Church from possible attempts of reduction, fully in keeping with the spirit of the Counter-Reformation reaction to Protestant attacks. For a discussion of the concept of potestas indirecta in Bellarmine and his thought interpreted as a political theology in service to the Counter-Reformation see: F. MOTTA, Bellarmino. Una teologia politica della controriforma, Morcelliana, Brescia 2005.

15 GALILEI, Edizione Nazionale delle Opere, vol. XII, 172.


G. GALILEI, Edizione Nazionale delle Opere, a cura di A. Favaro, Giunti-Barbera, Firenze 1929 – 1939, rist. anast. 1968.
R. J. BLACKWELL, Galileo Bellarmine and the Bible, University of Notre Dame Press, South Bend (IN) 1991. 
P. PONZIO, Copernicanesimo e Teologia, scrittura e natura in Campanella, Galilei e Foscarini, Levante Editori, Bari 1998.
P. A. FOSCARINI, Lettera del R.P.M. Paolo Antonio Foscarini carmelitano. Sopra l'opinione de' Pittagorici, e del Copernico. Della mobilita' della terra, e stabilita' del sole, e del nuouo pittagorico sistema del mondo, Napoli 1615.
A.C. CROMBIE, Da Sant’Agostino a Galileo, Feltrinelli, Milano 1982.
F. MOTTA, Bellarmino Una teologia politica della controriforma, Morcelliana, Brescia 2005.