1. Spiritual Topography: Celestial Bodies in
Motion---Dante’s Contribution to Galileo
Susan E. Bertolino
Intellectual Heritage Program
Temple University

2. ACTC Annual Conference
March 30th
, 2007
For that which moves is prior in nature to that which is moved.
Metaphysics—Aristotle
The existence of God can be proved in five ways. The first and most manifest way is
the argument of motion....For motion is nothing else than the reduction of
potentiality to actuality.
Summa Theologica—St. Thomas Aquinas
It would be a stretch indeed to insist that Galileo reached his conclusions about a
heliocentric solar system based on The Divine Comedy of Dante. Yet he never chose to
ignore the impact of art upon science. Early in his career, he gave a series of lectures on
Dante’s geography of hell; they were largely seen as failures, but it indicated that he
played with the idea that Dante himself wondered if the world was in stasis or in motion.
The universe that Dante creates is geocentric, based firmly on Aristotelian physics, later
echoed by the astronomer, Ptolemy, in his work The Almagest also known as The
Mathematical Collection, written in the 2nd
century, A.D. Yet Dante was writing his
masterpiece at a sensitive time when exile from his beloved Florence forced him to
contemplate all matters concerning the nature of truth. He certainly lacked the
mathematical tools of Galileo, but it is conceivable if not probable that he brought into
question all previous notions of theology, cosmology and the nature of man himself. This
paper will explore the images of motion that appear throughout Dante’s text and possibly
gave rise to Galileo’s belief that the medieval poet shared his doubts about planetary
motion and their relationship to the sun.
Galileo delved into The Divine Comedy as a debate in the Academy of Florence raged
on: “What were the location, shape, and dimensions of Dante’s Inferno?” (Mary Bellis:
Galileo Galilei—Biography 1.http://inventors.about.com/library/inventors/blgalileo.htm)
His research of Dante changed his fortunes, and he eventually landed a three year
appointment to the University of Pisa. What made Galileo’s work so important—was it
simply the act of inquiry itself or did he solve this 100 year dilemma in Florence? The
first step in deciphering that puzzle is understanding which cantos he deemed significant.
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3. Part of Dante’s task was to create hell, purgatory and heaven as believable through the
reader’s five senses. However, he was dealing with metaphysical realms of consciousness
that were unchallengeable by the Catholic faith, yet fallible through scientific
examination. Was Dante both a scientist and an artist? This question was uppermost in
Galileo’s mind. So he began with looking at key cantos that connote the possibility of an
earth in motion, keeping in mind that Dante would still illustrate a Ptolemaic
geocentricity.
Galileo examined the following cantos of the Inferno for his mathematical analysis of
Dante’s work: Canto I, III, IV, V, VI, VII, IX, X, XIII, XIV, XXIV, XXIX, XXX, XXXI,
XXXII and XXXIV. (Galileo Galilei, Two Lectures to the Florentine Academy, 1-9.
http://www.mtholyoke.edu/courses/mperterso/galileo/inferno.html) It would be
impossible for a paper of this length to explore all of his conclusions. It is only later in
other discussions that he considers Canto XVII, the bolgia of the violent against art, as a
precursor to the physical laws of motion. Some of these cantos only serve as a
mathematical exercise to prove that Dante constructed his hell with an educated grasp of
geometry. But Dante teased his reader with allusions to earth as both an imperfect sphere
and a place of movement. Consider these verses about his flight upon the monster
Geryon:
I think there was no greater fear the day
Phaethon let loose the reins and burned the sky
Along the great scar of the Milky Way
Nor when Icarus, too close to the sun’s track
Felt the wax melt, unfeathering his loins,
And heard his father cry, “Turn back! Turn back!”
(Dante Alighieri, The Inferno, vs. 100-105, pg. 137)
Dante used Greek mythology liberally throughout the poem. The reference to both
Phaethon and Icarus is telling. Phaethon drove the chariot that took the Sun from dawn to
dusk, falling to his doom as he was unable to handle the task. Icarus discovered the joy of
flying as he crept too close to the Sun’s heat and plunged to his death. Both myths
suggest an earth that moves in relation to a changing sun; the earth is in its rightful
proximity in order to gain sustenance from the sun’s rays, but woe to the mortal who
veers too close to those powerful beams. Both men are testimonies to the breadth of
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4. motion on earth while suggesting that the sun is also moving, a theory Galileo later
proves in The Starry Messenger with his discovery of sunspots through his telescope.
Both Dante and Virgil flee the icy dwelling of Lucifer in Canto XXXIV; this
underbelly of hell suggests again an earth that rotates its axis as the narrator describes the
changing sun:
“Get up. Up on your feet,” my Master said.
“The sun already mounts to middle tierce
And a long road and hard climbing lie ahead….
“Before I tear myself from the Abyss”
I said when I had risen, “Oh my Master,
Explain to me my error in all this:
Where is the ice? And Lucifer----how has he
Been turned from top to bottom: and how can the sun
Have gone from night and day so suddenly?
(Dante, The Inferno, verses 95-105, pg.268, Italics are my own.)
We read on in the text that Virgil tells his companion that they are now on the other side
of the world, the Southern Hemisphere, where they now can begin their climb up Mount
Purgatory. Virgil explains that the sun they viewed when they had descended into hell
was now in a different position because they had traveled such an extreme distance---
from one hemisphere to another. But it also indicates a sun that obeys the shifting
movement of the earth. If the earth stood still, why would one side of the planet have the
sun positioned differently? Dante does not explore that question, but it does suggest itself
as his own musing on earth’s physical relationship to the heavens.
Yet it is in Paradiso, Dante’s most complex work within the epic poem, where the
struggle between earth and celestial bodies perform a dance that implies that all is not
right with the Ptolemaic universe. Copernicus had yet to be born, but other minds were
still contemplating the validity of geocentricity. Dante, like Galileo, was an obedient
Catholic, yet viscerally critical of the corruption within the Church. As a man in exile
with the inheritance of his children in doubt, he had little to lose in delving into the
mysteries of cosmology that had been accepted for over 1000 years.
The inhabitants of the Inferno were fixed, unable to progress from their final
destination; the penitents of Purgatorio traveled a vertical distance in order to obtain
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5. spiritual cleanliness, but it is only in Paradiso where the souls know freedom of
movement. Aristotle believed that God himself moves the celestial realm through the
power of his love. Dante endorses this view, writing in Canto 1: “The glory of Him who
moves all things rays forth through the universe, and is reflected from each thing in
proportion to its worth.” (Paradiso, versus 1-3, pg. 596) To say that Dante is challenging
the Aristotelian/Ptolemaic paradigm is erroneous; however, in his search to fuse
metaphysical cosmology with moral order, he suggests that earth itself lacks the primacy
that the Catholic Church later used as a weapon to defeat Galileo’s masterpiece,
Dialogue Concerning the Two Chief World Systems. The main evidence for this
hypothesis lies in the final cantos, when Dante is purified enough to glimpse the Creator
in his glory.
Dante may believe that the world is the center of the heavens, but in the final cantos of
Paradiso, he sees the insignificance of the earthly realm. Beatrice introduces this in Canto
XXVIII:
The physical spheres are graduated in size
According to the power that infuses each
And fixes it to its station in the skies.
The greater good intends a greater grace
A greater body can hold more of good
If all parts are perfect, as in this case…..
If you will measure not by what appears
But by the power inherent in these beings
That manifest themselves to you as spheres. (Dante, versus 65-75, pg. 844)
Beatrice is referring to the Angel Hierarchy that God maintains in each sphere, ranging
from the simple angels, the Cherubim to the Seraphim. God maintains these as mirror
images of the Divine; thus the angels who are closest to God (the Seraphim) reflect his
majesty the most keenly. As John Ciardi writes in his notes on his translation, “God
conceived as the circumference of the physical universe…is powerfully relevant to
Dante’s belief that physical and spiritual law co-exist…as twin manifestations of one
will.” (Ciardi’s notes to Canto XXVIII, pg.848) So Dante reinforces Aristotelian
philosophy of primal energy in the universe. But Ciardi also notes a problem that he sees
as recognizable to Dante the author:
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6. If the larger physical sphere corresponds to the smallest angelic sphere, what then of
the assertion that a larger body contains more good than a smaller one if both are
perfect?
Dante…must have grasped that the greater power results from closer proximity to God;
the whole journey of the Comedy is scaled to that proximity. It is odd that Beatrice…
does not mention proximity to God as the essence of the mystery….Dante certainly
implies that we must ponder these points. (Notes to Canto XXVIII, pg. 848, italics
are mine.)
If spheres can range in size, then they also not only can change their spiritual essence, but
from a scientific viewpoint, they can be composed of different elements. Galileo never
goes forth to examine what we now know as the different chemical components of each
planet---he had enough trouble convincing people that the moon was not a smooth and
perfect sphere. But Dante himself seems to be troubled by this notion of physical
perfection as it corresponds to spiritual truth.
Dante learns in the Empyrean that earth may be God’s creation, but it pales in
importance to the heavenly realm. In Canto XXX, he writes: “Here I concede defeat. No
poet known, comic or tragic, challenged by his theme to show his power, was ever more
outdone.” (Dante, verses 22-24, pg, 861) He feels helpless before the magnificence of
God’s kingdom; moreover, he cannot articulate the celestial realm. A poet with so many
claims to language now admits that the heavens are beyond his human understanding. Yet
the desire to comprehend still remains. In Canto XXXI, he writes: “Without having fixed
on any part, my eyes already had taken in and understood the form and general plan of
Paradise.” (Dante, versus 52-54, pg. 871) But following the blueprint cannot be
enlightenment of God’s mysteries. What can remain? It is Bernard, the mystic, the
founder of the Cistercian Order, who points out the earth to him and cautions: “Dear son
of Grace,” he said, “you cannot know this state of bliss while you yet keep your eyes
fixed only on those things that lie below.” (Dante, verses 112-114, pg.873) Dante writes
these words, knowing that death soon awaits him, so he is already traveling in his mind to
the other side of eternity. But what does this indicate for the living? Scientists like
Galileo will read his words and agree that the earth alone cannot be the center of the
universe; one who seeks knowledge can find it through both God and science, using
mathematics, not poetry, as the new tongue.
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7. Galileo readers are aware that he considered Dante’s work as a forerunner to his own
research. One cannot insist that Dante was attempting to revolutionize astronomy; he
both lacked the skills and the interest. But if Galileo himself was willing to devote study
to The Divine Comedy to see what mathematical secrets it rendered, then it is fair to
assume that Dante himself questioned the physical nature of the universe, even if he used
the standard models of medieval times. Certainly without Dante, Galileo would have
made his assertions for a heliocentric solar system. But it is fair to claim that Dante
himself would have found Galileo’s discoveries both intriguing and possibly even true.
Each man was on a personal quest to solve his own mystery, and the intellectual world
has benefited tremendously from their respective bravery in their writings.
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8. Works Cited
“About Inventors: Galileo Galilei—Biography”. Mary Bellis.
<http://inventors.about.com/library/inventors/blgalileo.htm
Alighieri, Dante. The Divine Comedy: The Inferno, The Purgatorio and The Paradiso.
Translated and annotated by John Ciardi. New York: New American Library,
2003.
Galilei, Galileo. Two Lectures to the Florentine Academy On the Shape, Location and
Size of Dante’s Inferno. Originally published in 1588.
<http://www.mtholyoke.edu/courses/mpeterso/galileo/inferno.html
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