of ancient heretics alongside recent heretics, especially Luther and
Calvin. It had been the duty of the Dominican Order, since 1216, to
preach the Gospel and combat heresy. Father Petreto censured several heresies that Bruno defended, although he too did not mention Bruno’s name. Instead Petreto credited such heresies and errors to
whomever most infamously asserted them, or to broad groups like
‘the philosophers’.
Alongside each heresy, Petreto briefly explained why it is false.
For example, he denied the claim that ‘the world is eternal’, which
he attributed to Aristotle. 12 And he blamed Porphyry for the belief that ‘the soul is happy to flee from every body’, but denied it by
arguing that since the soul is the form of the body ‘it is not repugnant to unity with the body.’13 Petreto attributed the heresy that ‘the Holy Spirit is the soul of the world’ to Peter Abelard: Petreto countered that ‘Since God is perfect, it is impossible that He is part of a composition. ’14 Against the claim ‘They posit something of God as soul of the world,’ he replied, ‘But we assert that this is wholly false;
because God does not come into compositions. ’15
Kepler Announces Life in Other Worlds!
Other admirers of Copernicus and Pythagoras explored the idea
that the world has a soul and many worlds exist. Consider especially
the case of the young German astronomer Johannes Kepler. Like
his parents, he followed the reformed Christian religion of Martin
Luther, the ‘new Porphyry’, as Pope Leo x maligned him.
As a student at Tübingen, Kepler’s teacher Michael Maestlin
convinced him of the theory of Copernicus. Hence in 1593 Kepler
began to draft a dissertation in which he mathematically analysed
what the heavens would look like to observers standing on the
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Moon. To present the subject, he sketched an introduction that
described a voyage to the Moon. He read Lucian’s ‘True History’.
Although Lucian had warned that it was fiction, Kepler was
impressed and in some sense he did believe it to be true. Also in
1595 he read Plutarch’s story of the Moon. Kepler’s interest in lunar
astronomy and geography led him to consider seriously whether
there is life on the Moon. He conjectured that the Moon and the
planets resemble the Earth. He wondered whether those other
worlds were inhabited.
Kepler began to draft his own story about a dream, a lunar
journey.16 In his story an old mother reveals to her son that she could talk with the Moon and showed him the secret art of conjuring spirits. Then an alien daemon took the mother and boy on a dangerous voyage to the Moon. They travelled there to meet its
inhabitants, who hid in caves to protect themselves from the Sun’s
heat, and to discuss their astronomy. They saw strange things and
beings, including monstrous snakelike creatures that shun the Sun,
and others who daily die by daylight and return to life at night. But
Kepler did not publish this.
In 1594 the 22yearold Kepler had become a teacher of mathematics in Graz, Styria (Austria). As an official mathematician of the district of Graz, he was expected to make astrological predictions. He did not really believe that astrology controls individual events. Still, in 1595 Kepler predicted that there would be a bitterly
cold winter and the Turks would attack. Surprisingly, his predictions
turned out to be correct, so he became a celebrity. 17 More importantly, Kepler worked on astronomy, fascinated by the Copernican theory. He struggled to answer questions such as why were there
only six planets, including the Earth.
On 19 July 1595 Kepler was teaching a class when suddenly he
had an idea. By interspersing geometric regular figures between
the planet ary orbits, he might be able to calculate the separations
between the orbits. Kepler wrote: ‘I believe that it was by divine
ordin ance that I obtained by chance that which previously I could
not reach by any pains; I believe that so much the more readily
because I had always prayed to God to let my plan succeed, if
Copernicus had told the truth. ’18 Kepler calculated the distances between the orbits of the six planets by interspersing the five regular solids between them. It seemed clear evidence of God’s wisdom.
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Kepler believed that God ‘revealed’ to him this discovery, which
had quietly waited since the dawn of Creation to be grasped by
humans:
It will never be possible for me to describe with words the
enjoyment which I have drawn from my discovery. Now I no
longer bemoaned the lost time; I no longer became weary at
work; I shunned no calculation no matter how difficult. Days
and nights I passed in calculating until I saw if the sentence
formulated in words agreed with the orbits of Copernicus,
or if the winds carried away my joy. In the event that I, as I
believed, had correctly grasped the matter, I vowed to God
the Omnipotent and Allmerciful that at the first opportunity I would make public in print this wonderful example of His wisdom.19
If anything did not quite work in the numerical and geometric harmony of the universe, Kepler commented that he hoped Pythagoras might perhaps rise from the dead to help him – which did not
happen, he wrote, ‘unless perhaps his soul has transmigrated into
me’.20 But Kepler did not believe in numerical mysticism.21
In 1596 Kepler published his Cosmographical Mystery, endorsing
the Copernican theory. He said Plato and the Pythagoreans ascribed
great importance to the five regular solids in the order of the universe. Echoing ‘Plutarch’, Kepler stated that Pythagoras himself knew
this.22 Kepler wanted to include an introductory chapter explaining the consistency of Copernicus’s theory with the Bible, but the senate
of the University of Tübingen censored that part. Kepler acquiesced:
‘we shall imitate the Pythagoreans also in their customs. If someone
asks us for our opinion in private, then we wish to analyse our theory
clearly for him. In public, though, we wish to be silent.’23
Kepler wrote that Pythagoras had been reborn as Copernicus.
At the very start of his book, Kepler included a poem he wrote:
What world, what cause, God, reason for creating,
how God’s numbers, which many regular magnitudes,
that made six circuits, that each orb
falls in intervals, that both Jupiter & Mars
their orbs not primary, interspersed in gaps:
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All this Pythagoras taught you with five figures,
thus this example teaches us, that we can be reborn,
two thousand mistakes, years, he becomes Copernicus,
hence you are called the best observer of the World.
But the seeds you discovered did not delay the crops.24
Thus Kepler linked the Creation of the cosmos with the transmigration of souls. He wrote nearly the same poem in a letter to Duke Frederick of Württemberg, early in 1596, but he replaced its last line
with these: ‘But you discovered Frogs, which is from seedful pleasure,
with a herd of pigs posing among the trough of swine’, 25 which show a resentment towards the unenlightened mob.
A year later, in 1597, Kepler sent a letter to a young and relatively
unknown professor at the University of Padua, Galileo
Galilei. In
it Kepler tried to convince Galileo to publish on the Copernican
theory and he referred to Pythagoras as one of their true masters:
‘although you warn discreetly and secretly, by your own example,
that one should retreat before common ignorance, one should not
rashly incite or oppose the madness of ordinary learned men – in
which respect you follow our true masters, Plato and Pythagoras.’
In 1600 Kepler was appointed imperial mathematician to
Emperor Rudolf ii. Although Rudolf had been raised in Spain,
fortunately for Kepler he had withdrawn from Catholic observances
and tolerated the Protestants.
One of Kepler’s friends, Edmund Bruce, wrote him letters
expressing eccentric opinions about astronomy. Bruce was an
Englishman who studied and lived in Padua and participated in
intellectual circles. Bruce knew Galileo and informed Kepler about
him. For years Galileo had not replied to Kepler’s letter of 1597.26
In 1603, however, Bruce sent Kepler a frank letter voicing opinions
that resemble those of Giordano Bruno:
I have many doubts in astronomy about which you alone
[can] make me more certain. For I think that there are
infinite worlds. Each one of these worlds is finite, as if the
Sun’s centre is in the middle of the planets. And just as the
Earth does not rest, so neither does the Sun. For it rotates
most rapidly in its place around its axis, the motion of which
the other planets follow. I think that the Earth is one among
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these [planets] but each [moves] more slowly the further it
is from it [the Sun]. The stars are thus moved like the Sun,
but they are not, as are the planets, driven around in a circle
by the force of this body [the Sun], since each one of these
[stars] is a Sun – and not part of this, our smaller world of
planets.27
Bruce argued that the elements (earth, water, air, fire) exist not only
on Earth but in outer space. Such ideas seemed ‘probable’ to Bruce,
so he asked for Kepler’s opinion. Mysteriously, Bruce didn’t mention
Bruno. Not much more is known about Bruce: ‘Unfortunately after
this letter, the brief trail left by Edmund Bruce dies out. Was he
able to visit Kepler in Prague on his way back to England? Indeed,
did he ever return?’28
According to Aristotle and ancient Greek astronomers, no
change exists in the heavens. Yet a bright new star suddenly appeared
in 1572, and vanished. Now, in 1604, another bright star appeared.
For a year Kepler carefully observed it and published a book about
it in 1606. He there said that heavenly matter is changeable, and he
analysed his observations in terms of ‘the Copernican hypothesis’.
Kepler argued that, contrary to what theologians might claim, the
new star was no miracle. Then, as he was about to opine about its
origin, Kepler wrote:
First I will say something: so that others may have material
to discuss copiously. A certain Pythagorean brings to mind
this Virgilian passage:
In the beginning, the sky and Lands, and regions of water,
Shining globe of the Moon, and Titanic stars
Spirit nourishes within; the totality, infused through
the limbs,
a Mind agitates the mass, & intermixes itself with
the great body.
Thus from Aristotle: Both plants and animals originate from
earth and fluids [ humore] : because there is a fluid in the earth, a fluid spirit, in its entirety indeed a universal animal heat:
by which Scaliger thought that these words lead us into the
occult mysteries of nature.29
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The next chapter compared the nova of 1604 to the nova of 1572.
However, in another section of the same book Kepler explained that
he believed in the soul of the world: ‘If nothing were alive, it would
vivify all matter, as the Earth; if nothing moved, it would attract
everything to itself, some more than others.’30 He argued that this soul was responsible for converting the sweat of women and dogs
into fleas, dew into beetles, marshland into frogs, water into fish, soil
into plants, corpses into worms, and so on, and ethereal regions into
comets and stars. Kepler argued that a ‘seminal reason’ with some
sort of moisture generates various species.
In describing such ideas, Kepler gave credit to Cornelius
Gemma, a German physician, astronomer and astrologer. Gemma
had described the new star of 1572 two days before Tycho Brahe.
More importantly for our discussion, however, Gemma had argued
that ‘all that is called the world or universe’ is a single animal
endowed with an intelligent mind and one spirit. 31 He had also paraphrased a relevant quotation: ‘In the beginning the sky & lands,
regions of water, Spirit nourishes within, &c. Aen. 6.’32 Moreover, in a work published in 1569, Gemma had argued that what some people
called ‘the soul of the world’ was the same agency that Christians
called ‘the Holy Spirit’, and that by it the heavens are moved and
heat is diffused in the atmosphere, and so forth. 33 Again, these notions remind us of the heretic from Nola.
At some point, Kepler heard about Bruno’s execution. Later, in
1607, he discussed the tragic event in a letter to a friend, the physician Johann Brengger. This letter is significant also because in it Kepler discussed his own belief in many worlds and alien life forms:
You think that the orbs of the stars are perfectly unmixed
and simple; but in my opinion they resemble our Earth. You,
a philosopher, would remit the question to a philosopher;
but Experience should speak, if she could be interrogated.
[emendation] But Experience is silent, since nobody has
been there; whence she neither affirms nor denies. I myself
argue as you do, by induction from the Moon, which has
many points of similarity with the Earth. And moreover I
attribute moisture to the stars, and tracts which are rained on
by evaporation, and living creatures to whom this is advantageous. For not only that the unfortunate Bruno, who was 108
Aliens on the Moon?
broiled on a wood fire at Rome, but my friend Tycho Brahe
as well, held this opinion, that the stars have inhabitants. To
this I agree more readily, that I hold, with Aristarchus, the
motion of the Earth as well as of the planets.34
Brengger replied that he did not know that Bruno had been burned
and said he felt pity for him. He asked whether Kepler was sure about
this. Kepler then replied that he had learned about Bruno’s execution
from his friend Johann Wackher: ‘I learned from Master Wackher
that Bruno was burned in Rome, he endured his execution with
firmness. He had maintained that all religions are vanity. Identifying
God with the world, the circle, the point. ’35 Finally, Brengger wrote to Kepler: ‘I can’t stop being perplexed by the dementia of Bruno.
What did he stand to win by enduring such tortures? If there were
no God to punish the crime (as that was his opinion), could he not
impudently play a bit in the comedy to thus save his own life?’
> In 1609 Kepler published his Astronomia nova, vigorously
defending the Earth’s motion as fact. He argued that in theology
authority carries most weight, but that in philosophy reason is more
important. Following Copernicus, he criticized Lactantius for denying the Earth’s roundness, and he also criticized St Augustine and the Inquisition: ‘the Holy Office nowadays is pious, which, though
allowing the Earth’s smallness, denies its motion.’36 Kepler argued that the truth is more pious, and that therefore he proved that the
Earth ‘is carried along among the stars’.
Meanwhile, a Jesuit theologian named Nicolaus Serarius wrote
a commentary on the Book of Joshua, in which he took the opportunity to criticize Copernicus and the Pythagoreans for asserting the Earth’s motion: ‘such a hypothesis, if seriously held as true, I
do not see how it can be devoid of heresy.’ He said that the Bible
always attributes rest to the Earth, and that where it says that the
Sun and the Moon do not move it is by a miracle. This Jesuit then
noted that ‘Al philosophers agree that this opinion [the Earth’s
mobility] should be rejected and condemned, except for a few such
as Nicetas [Hicetas of Syracuse] and the Pythagoreans, relatives; all
statements of the Holy Fathers [deny it], all Theologians in all [the
monastic] schools. ’37
At the same time, an innovative telescope enabled Galileo to
seek visual proof of Copernicus’s theory. In 1610 he published his
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Message from the Stars.38 He reported that the Milky Way is composed of stars, that Venus has phases, and that four bodies orbit Jupiter.39 But above all, Galileo reported having seen mountains and valleys on the Moon. His findings raised sensational questions: is the
Moon really another world? Is Jupiter another world?
Back in 1591, in his book On the Immense and the Innumerable,
Bruno had insisted that ‘There are innumerable distinct worlds,
which we call stars.’40 Now, on the title page of Galileo’s book, Galileo boldly announced the discovery of ‘innumerable stars’.41
Bruno had also argued that multiple moons exist, not just one. 42
Now, similarly, Galileo reported that four bodies orbit Jupiter, just
like our Moon around the Earth.43 Furthermore, Bruno had proposed that the Moon and other heavenly bodies are surrounded by a kind of ‘air’, like the Earth.44 Similarly Galileo now argued that
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