Galileo: heretic or hero? What are the facts?

Galileo: heretic or hero? What are the facts?

Noel Roberts

Dr Noel Roberts, formerly Associate Professor of Chemistry at the University of Tasmania, has an Honours Bachelor of Divinity degree, specialising in Hebrew, and is expert in Greek, German and other languages. He wrote the book 'From Piltdown Man to Point Omega: The Evolutionary Theory of Teilhard de Chardin' (Peter Lang, 2000), and has written many articles on Newman and several on Galileo. He recently contributed a chapter to a history of Christianity.

During the seventeenth century Christian Europe witnessed an explosive interest in and understanding of the natural world. The stranglehold of the ancient Greek philosopher Aristotle on people's understanding of the natural world was broken and a new way of probing nature arose, though much of Aristotle's philosophical thinking remains valid to this day.

Catholic and Protestant Christians made the major scientific discoveries of the 17th century and many of them were ordained clerics.

At the dawn of that century, on 17 February 1600, the Inquisition sentenced Giordano Bruno, a Dominican priest, to burning at the stake for heretical views about the divinity of Christ, the salvation of the Devil and other matters. Although Bruno was a fervent disciple of Copernicus his astronomical views had nothing do with his death sentence even if it was popularly believed to be the reason for his condemnation.

The Bible expressly states that the world had a beginning, that the earth was fixed in the firmament and that Christ came once and for all to this planet to save sinful humanity. When astronomers began speculating about the universe - its age, whether it was eternal or had a beginning, whether other universes existed that needed God's saving help and the place of the earth in the cosmos - theologians became concerned because many of the ideas appeared to be in conflict with sacred Scripture.

To many astronomers of the time it seemed absurd that God had created this colossal universe purely for the sake of human beings. It could have been said in reply that God becoming man to save humanity seems even more absurd: for throughout the Scriptures God behaves in ways that defy human thinking.

Copernicus' heliocentric theory aroused little interest from the Church for 50 years with the most scathing condemnations coming from Protestants, in particular Luther and Melanchthon.

Initially the Catholic Church saw his system as an hypothesis enabling a simpler method of calculating the motion of the heavenly bodies than the Ptolemaic system, and not as a scientific fact. This was certainly the position of Cardinal Bellarmine who held that the planetary theories of Ptolemy and Copernicus were mere hypotheses not susceptible to physical proof.

The question of the movement of the earth only reached the stage of genuine conflict towards the end of the 16th century.

Another reason for its initial mild reception was that Copernicus was not a great observer like the astronomer Tycho Brahe who refused to become a follower of Copernicus. Much of the argument in favour of the heliocentric theory of Copernicus turned on its greater economy and mathematical appeal.

Central figure

Galileo Galilei (1564-1642) is, by any reckoning, a central figure in the scientific revolution of the 17th century. His work in physics, astronomy, and the methodology of science has earned him a well-deserved place in the annals of science.

Pope Urban VIII was a friend of Galileo and had even written a Latin ode celebrating Galileo's discovery of sunspots. However, by late 1632, after publishing Dialogues on the Two Chief World Systems, Galileo was ordered to Rome to be examined by the Holy Office of the Inquisition. This was tantamount to a charge of heresy, and he was called to repent.

He was charged with teaching and defending the Copernican doctrine that holds that the Sun is at the centre of the universe and that the Earth moves. This doctrine had been declared heretical in 1616, and Copernicus' book had been placed on the index of prohibited books. Galileo's position was not helped by the fact that he put in the mouth of a foolish character, Simplicius, in Dialogues on the Two Chief World Systems, an argument that the Pope had once defended.

The Inquisition argued that the Copernican doctrine was contrary to Sacred Scripture. It is stated in both Psalms 93:1 and 96:10, "Yea, the world is established; it shall never be moved", while Chronicles 16:30 states, "Yea, the world stands firm, never to be moved". Psalm 104:5 says, "the Lord set the earth on its foundations; it can never be moved", and in Ecclesiastes 1:5 we read, "And the sun rises and sets and returns to its place."

Galileo argued that the doctrine of Copernicus was not at odds with Holy Writ. In a famous letter, dated 21 December 1613, to his good friend, former student and professor of Mathematics at Pisa, Fr Benedetto Castelli, a Benedictine priest, Galileo took a position reminiscent of St Augustine's views on interpretation of Scripture: not to take every passage literally, particularly when the Scripture in question is a book of poetry and songs, not a book of instruction or history.

The Scripture writers wrote from the perspective of the terrestrial world, and from that vantage point the sun does rise and set. While Galileo admitted that the Bible is an inspired text he held that two truths, biblical and scientific, couldn't contradict each other. Consequently if science achieved a true result the Bible should be interpreted in such a way as to accord with scientific truth.

Galileo wrote: "Since two truths can obviously never contradict each other, it is the part of wise interpreters of Holy Scripture to take the pains to find out the real meaning of its statements, in accordance with the conclusions regarding nature which are quite certain, either from the clear evidence of sense or from necessary demonstration."

Cardinal Bellarmine, the most influential member of the Sacred College and head of the Holy Office of the Inquisition, was more than willing to consider Galileo's position provided that "a real proof be found that the sun is fixed and does not revolve round the earth, but the earth round the sun."

Bellarmine conceded that "it would then be necessary, very carefully, to proceed to the explanation of the passages of Scripture which appear to be contrary, and admit that we have misunderstood them rather than pronounce false what has been demonstrated. But this is not a thing to be done in haste, and as for myself, I shall not believe that there are such proofs until they are shown to me."

The Cardinal had raised the very important question: What constitutes proof or demonstration of a scientific claim? It is a question that is hotly debated to this day.

Galileo thought he had the proof of the Earth's motion around the sun in his On the Ebb and Flow of the Tides. It was published in 1616, the year the Copernican theory was declared heretical, and later incorporated in Dialogues on the Two Chief World Systems.

Galileo argued that the motion of the earth, diurnal and axial, was the cause of the tides. He was wrong. Even if he had been correct the tidal argument does not deal directly with annual motion of the earth about the sun nor with the central position of the sun.

Paradoxically, Galileo had a better grasp of Biblical interpretation than did the Inquisition, whereas Cardinal Bellarmine had a better appreciation of what constitutes a scientific proof.

Official sentence

The official sentence against Galileo reads: "We say, sentence, and declare that you, Galileo, by reason of the evidence arrived at in the trial, and by you confessed as above, have rendered yourself in the judgment of this Holy Office vehemently suspected of heresy: namely, of having believed and held the doctrine, false and contrary to sacred and divine Scripture, that the Sun is the centre of the world and does not move from east to west; and that the Earth does move and is not the centre of the world; and that an opinion may be held and defended as probable after it has been declared and defined to be contrary to Holy Scripture."

On 22 June 1633 Galileo was condemned to penance and prison for life; but his friend, Pope Urban VIII, ordered that he could immediately return to the residence of the Florentine ambassador, and in December 1633 he was allowed to retire to his villa outside of Florence.

During this time Galileo completed his finest work, Discourses on the Two New Sciences (1638), while battling with blindness for the last years of his life. He died on 8 January 1642.

Paul Feyerabend, one of the most famous and intriguing philosophers of science of the 20th century, had this to say about the Galileo case: "The Church at the time of Galileo kept much more closely to reason than did Galileo himself, and she took into consideration the ethical and social consequences of Galileo's teaching too."

In October 1992 Pope John Paul II expressed regret for how the Galileo affair was handled.

There is another matter that could have landed Galileo in much hotter water than his support of Copernicus' heliocentrism: and that was his atomic theory. Redondi argues in his book Galileo Eretico (1983) on the basis of a document G3 sent to the Holy Office in 1624 that Galileo was under investigation for denying the doctrine of transubstantiation, viz, the conversion of the whole substance of the bread and wine into the whole substance of the Body and Blood of Christ, with only the "accidents" or "species" (i.e., appearances of the bread and wine) remaining.

Galileo argued in The Assayer (1623) that all reality was reducible to the effect of crude atomic particles upon one another and the senses, and that there could be no real distinction between "substance" and "accidents."

"I think", Galileo argues, "that tastes, odours, colours and so on as regards the object in which they reside are nothing but pure names and reside only in the feeling body, so that if the animal is removed all these qualities are taken away and annihilated."

Redondi was not given access to other documents about the Galileo affair, but in 1999 Mariano Artigas of the University of Navarra obtained access to another document from the Vatican Archives labelled EE291, dated 1631 or 1632, which repeated the same charge.

The author, Melchior Inchofer SJ, was a member of a special commission set up by Pope Urban VIII to investigate Galileo. Inchofer writes: "It immediately follows from the opinion of [Galileo] that in the Eucharist the accidental properties do not remain without the substance of the bread."

But for some reason the Holy Office saw no grounds for proceeding against Galileo. To explain the lack of action on the part of the Holy Office, Redondi proposed a reinterpretation of the Galileo affair in which Pope Urban VIII, "a former friend and admirer", had to face the accusation of Copernicanism, and not the more serious accusation of denying the doctrine of transubstantiation. Although there is no evidence that Galileo ever expressed an opinion on the Eucharistic doctrine of transubstantiation.


Now, four hundred years after it put Galileo on trial the Vatican is to complete its rehabilitation of the great scientist by erecting a statue of him inside the Vatican walls. The planned statue is to stand in the Vatican gardens near the apartment in which Galileo was incarcerated while awaiting trial in 1633.

Nicola Cabibbo, head of the Pontifical Academy of Sciences, says, "The Church wants to close the Galileo affair and reach a definitive understanding not only of his great legacy but also of the relationship between science and faith." As Paolo Galluzzi, head of the Florence museum, remarked, "even if Galileo had been wrong, you cannot judge scientific errors in an ecclesiastical court".

On 20 April 2009 the Vatican announced the publication of a new book Galileo and the Vatican co- authored by Mariano Artigas (deceased), the discoverer of document EE291, and Msgr Sanchez de Toca. It gathers together the documents of the commission created by Pope John Paul II on Galileo.

Msgr Sanchez de Toca admits, "The judges of Galileo, in addition to the obvious error of believing that the Earth did not revolve, committed the mistake of entering a field outside their competence. They thought the Copernicus system defended by Galileo with such vehemence endangered the faith of simple people and that it was their obligation to prevent it from being taught. This was an error and it is necessary that it be acknowledged."