historical novel originally published in Italy in December 2005 under the title
Eresia Pura by STAMPA ALTERNATIVA (ISBN - 88-7226-904-0)
translated from the Italian by Donald Boris Hope
It is the hot night of July 24th 1207.
We are at Nemi, in one of the outbuildings around the castle (the summer residence of the Cistercian monks of the
monastery of Sant'Anastasio alle Tre Fontane in Rome). Exhausted by the sultry heat and by fatigue, two lay brothers -
whose job is to cultivate the land and to look after the castle the whole year round - are talking late into the night.
Old Jerome hates and curses priests, monks, abbots, bishops and popes. Young Giordano is instead entirely absorbed in
the study of mechanics and mathematics. Both of them - during the winter - have the free run of the great library on
the ground floor of the castle; but the most rare books are probably hidden in a great cupboard, kept always locked,
on the second floor of the Saracen Tower. It's from one of the books out of this cupboard that Jerome copied many
pages in Greek, that he then passed on to young Giordano, who - thanks to his natural gift for figures - worked out
what they meant and thus wrote his first book, My Little Abacus, in which he explained the surprising and then still
unknown use of the new indo-arabic numerical notation. The book was then sold to a young Pisan merchant (a friend of
Raniero Capocci, the abbot of Sant'Anastasio and of Nemi), Leonardo di Bonaccio, who in turn developed it, producing
the first great treatise on the new Indian numbers, the Liber abaci, which was to mark a turning-point in the history
But how had the Greek pages come to end up in that book? And what was the text in question? And why had Giordano
already several times, for no apparent reason, betaken himself into the basilica of S. Pietro in Vincoli in Rome,
fascinated by the mosaic of St. Sebastian? And what were the General of the Cistercian Order, Arnauld-Amaury, and
Pope Innocent III coming to do at Nemi the next day?
During the night Giordano relives, in a dream, a terrifying story that happened on the 22nd of July more than five
The great Armenian astronomer and mathematician Ananias of Shirak - persecuted by the church and the law for his
revolutionary ideas - has entrusted to three of his pupils (David, Eznik and Aser) the Keys of Knowledge, so that
they shall take them to the West. It is the year 662: the Arabs are making themselves the masters of everything,
and burning every book that they find in their path. The Keys of knowledge are revolutionary scientific discoveries
that can change the course of history and of mankind, the fruit of work by the Indians and Chinese. But so far the
Orientals have not succeeded in impressing a decisive turn on that history. It is the turn of the West. Ananias'
three pupils take different roads. Aser leaves his 'Paulician' Christian community of Kibossa and arrives in Rome
together with the Byzantine emperor Constans II: inside a leather bag from which he never lets himself be parted,
he keeps two manuscripts of no apparent value. The letters of an almost unknown Byzantine writer, Theophilact
Simocattas, and a palimpsest with some plays by Plautus rubbed down to make room for the Old Testament. Interleaved
in these two manuscripts are many pages in Greek with the Keys of knowledge. After having had the mosaic icon of St
Sebastian installed in the basilica of San Pietro in Vincoli, Aser goes with a learned Roman prelate to the lake of
Nemi - to just where once the temple of Diana used to be - to observe a strange phenomenon in the ground. But he is
knocked down, tied up and burnt alive by his companion, who robs him of the two manuscripts hidden in the leather
bag fastened whit a bronze buckle inlaid with designs in gold.
Giordano wakes up, and - wracked with anguish - tells his companion the nightmare that he has just lived through.
Old Jerome is at first incredulous, but then understands that something strange is really happening. The book from
which he had copied the pages in Greek with the revolutionary Indian numbers was in actual fact a text of some
comedies of Plautus… although he was sure that it was not a palimpsest. Then Giordano's exact description of the
bronze buckle makes him jolt with astonishment. He fetches a bag and shows it to the younger man: he found it the
day before, while working in the fields near the lake, just where there had once stood the temple of the goddess
Delirium, nightmare, legend, reality… by now the two men do not need to probe any more deeply. They realise that
all this is not just fortuitous. Something serious is threatening the world… and it certainly has something to do
with the meeting at Nemi between the Pope and the General of the Order and papal legate in Provence, Arnauld-Amaury.
Giordano hides himself in the Saracen tower, in a niche on the second floor, behind some shelves loaded with books.
It is just here - where there is the small and mysterious book-case - that the meeting takes place. They talk about
the false Donations of Costantine. Finally, Innocent III decrees the extermination of the heretic Cathars and of the
people of Occitania. Then he takes out of locked cupboard three precious manuscripts, containing "the essence of
secular and revolutionary science, the knowledge that could endanger the future of the realm of the Church", and
consigns them to the legate Arnauld-Amaury, so that he shall take them with him to France and have them safely kept
by Friar Elia. These extraordinary books - the letters of Theophilact Simocattas and two books of comedies by
Plautus - are no longer safe in the Saracen tower of Nemi, because part of their contents have already been divulged.
He summons his counsellor-confessor Abbot Raniero Capocci and shows him My little Abacus, by Jordanus de Nemore…
which had been sold to the abbot's own Pisan friend Leonardo seven years before, by a young man "of agile physique,
short in stature and with thick black curly hair…"
Giordano is discovered, but manages to run away, and - by means of the drain that leads from the lake of Nemi into
the valley of Aricia - he takes ship and lands at Marseille; from there he sets out for the first city mentioned
by Arnauld-Amaury: Béziers, the Devil's lair, the Synagogue of Satan.
From that moment on there is a change in the life of the young scholar Giordano Nemorario (who henceforth will call
himself Palis Jordanus): his continual devotion to study is overlaid with other preoccupations. He goes on trying
to trace the three precious manuscripts; but what the Church, with the interested help of allies like the kings of
France, is preparing to bring about - that is, the extermination of an entire, free and rebellious people - comes
to involve him more and more.
He is welcomed by the tolerant people of Béziers, whose sense of hospitality, taste for life and love of justice
persuade him to stay there; to share his destiny with them. Giordano meets, and falls reciprocally in love with,
Jolanda. For a time they work for Shimon, a Jewish merchant, the father of Sara and David, two children who become
much attached to the young couple. Then they move into the free quarter of town, the parish of La Maddalena, into
the Cathar's house, where Giordano opens a school to teach the children of the city their letters and numbers. On
the 14th of June 1208 the papal legate Pierre de Castelnau is assassinated by a squire of Count Raymond VI of
Toulouse, the lord of the Languedoc. This bloody act gives the pope an immediate reason to sound the war trumpets.
Giordano, in the meantime, has heard the preaching at Béziers of Guilhabert de Castres, the future Cathar bishop who
will become so important in his life.
While preparations for war get under way, Giordano does not give up hope of finding the manuscripts; but he cannot
even get near to the Cistercian mother-abbey of Cîteaux. So he goes on with his own mathematical and mechanical
studies. He loves Jolanda, and she is going to have a child by him: she is sure it will be a girl, with long
blonde hair. They will call her Esclarmonde.
The command of the powerful Army of Christ (which is over five hundred thousand men strong) is assigned to
Arnauld-Amaury. On the 21st of July of 1209 this crusading army lays siege to Béziers. The citizens unanimously
reject the demand made by the white abbot that they hand over 223 people (and among them the little astronomer
and mathematician Palis Jordanus from the suburb of La Maddalena), and get ready to defend their freedom. But
during the night a number of the brigands and murderers whom the crusaders have recruited, hide themselves in
the water-cisterns built against the inside of the walls, getting in through the tunnels built by some traitors.
The next day, the feast-day of St Mary Magdalen and of the liberation of Béziers, while the traitors make a show
under the walls of the cathedral of St.-Nazaire, thus distracting everyone's attention, the brigands and murderers
get inside the walls on the other side of the city, by the Porte St.-Guillaume, and open the gates and passages:
in a few hours the entire population are exterminated. The powerful engines of war constructed by little Palis
Jordanus have been of no use at all. Among the thousands of corpses that cover the floor of the church of St
Mary Magdalen, Giordano (disguised as a crusader by Shimon, before Shimon's own death) finds David, little Sara
and his own Jolanda with her belly cut open. His little Esclarmonde, carved out of her mother's womb, has been
murdered before she could see the light of day. Giordano - in a state of desperation - nonetheless keeps the
promise that he made to his friends the captain of the garrison, Bernard de Servian, and to Shimon and to
Jolanda, and leaves the city through a tunnel that takes him from the new castle to a place right outside the
walls, in a little wood. He collects his books, hidden by Jolanda in the old mill, and makes his way towards the
refuge of the Cathar bishop Guilhabert de Castres, in the Pyrenees: the impregnable pentagonal castle of Montségur.
While the crusade against the rebellious people of Occitania goes on, and the army of Christ destroy fields, towns,
crops and entire populations, Guilhabert urges Giordano to leave Occitania, to continue his studies elsewhere, and
never to give up hope of being able - one day - to wrest the keys of knowledge from the ferocious white abbot.
Giordano leaves Montségur and strikes north, towards a new life.
While the epic tragedy of Occitania and the Cathars - with human bonfire after human bonfire - goes on, on the 9th
of April of 1229 in the Great Hall of the University of Paris there is a meeting of all the masters of the University.
Many students have been massacred by the city authorities. Only the theologians fail to come to the meeting. It's a
campaign for the freedom to teach, for freedom of thought. The last to speak is the mathematician and astronomer
Giovanni de Sacrobosco, the most distinguished person present. In a most persuasive speech, he too declares himself
in favour of giving up the university. As he leaves the hall, he firmly tightens the belt with the bronze buckle
inlaid with designs in gold.
Giordano Nemorario - for he, in fact, it is - having fled as far as Scotland, has taken the name of Giovanni de
Sacrobosco. Having joined the Trinitarian order, and completed his studies at Oxford, he eventually comes to Paris
and enters the monastery of the Maturins, very near to the University. As Giovanni de Sacrobosco he writes only
three books: besides his Algorismus (Arithmetic), and De anni ratione (On the calendar), he writes an astronomical
work that for several centuries remains the standard text-book in all the universities of Europe. De sphera (The
Book of the Spheres). As Giordano Nemorario, however, he writes a great many books on mathematics and mechanics,
whose inspiration seems to spring out of nowhere, such as Aritmetica, De numeris datis (On given numbers),
Algorismus demonstratus (The Proofs of Arithmetic), De triangulis (On Triangles), and Elementa Jordani de
ponderibus (Jordanus on weights and measures).
After leaving Paris and its university, he sets off on a long journey in search of the three precious manuscripts,
but does not find them at Cîteaux. He goes to all the Cistercian abbeys and libraries, including Fontfroide,
to which Arnauld-Amaury had left some books before he died. But all in vain. So he goes back to Montségur, where
he meets the third daughter of the lord of the castle, Esclarmonde de Perella, a most beautiful girl of twelve
with long blonde hair. She is blind, and lives almost always in the castle, with her grandmother. Giordano feels
a deep affection for this girl, who for him seems to represent his own little Esclarmonde, who was murdered at
He stays for some months there, letting himself be soothed by the peaceful life of the castle, but also
collaborating with Guilhabert de Castres to improve the library of Montségur, which contains some very important
books of religion, philosophy and science. A group of Cathar perfecti continually transcribe the texts, which are
then disseminated among the people. Thousands of copies are made of works ranging from Aristotle to the Gospels,
and hence distributed throughout all of war-torn Occitania; the Cathar bishops know that spreading the Word of
Christ and of love will not suffice to make the people rebel: they also need knowledge, and the power of reason.
Then Guilhabert urges Giordano to go back to the university in Paris, to carry on his struggle as a scientist,
to keep looking for the keys of knowledge. Not to neglect this mission out of love for little Esclarmonde.
Giordano goes back to Paris, where he resumes teaching, still under a false name… and thus the Maturin monk - and
mathematician and astronomer - Giovanni de Sacrobosco, follows from far away the course of the war in Occitania,
that is already drawing to its end.
It's almost summer, in the year 1243. Occitania has been torn to pieces, conquered and subdued, its cities razed
to the ground. There remains only one small knot of rebels ensconced in the small castle of Montségur, together
with the last few Catharist preachers who have so far escaped the burnings. It is the last flame of hope and freedom
in the whole of Christendom. Esclarmonde, too, is a prisoner of the siege in that castle.
Giordano hurries to England, to his friend and fellow-scientist Roger Bacon. He meets him on Salisbury plain, in
the ruins of the prehistoric temple of Stonehenge, because it is time for the beginning of the summer solstice.
It's the morning of the 21st of June. While he was studying in Paris, Roger Bacon had confided to Giordano that
he was making experiments with the black powder… which could perhaps be of use - among its other possibilities -
in battle. Unfortunately, he has as yet made no progress in that direction. But at the very moment of sunrise
Giordano's mind is shot through with memories: first, of the rays of sunlight coming through the iron gratings
of the castle of Monségur, to rest on the lightless eyes of Esclarmonde; then he feels the force of the sunrise
driving him towards other memories, into another tower… the Saracen tower of Nemi, some forgotten words, a phrase
spoken by Arnauld-Amaury to Innocent III. Friar Elia as the ideal custodian for precious books, in the year 1207…
what monastery could that be? And Roger Bacon shows him the mistake that he's been making for all these years.
They weren't talking about a Cistercian abbey… but about a Benedictine one! And in fact Friar Elias was the abbot
of the Benedictine abbey of Ste.-Colombe at Sens, a few hours walk from Paris! The keys of knowledge might really
be there. Giordano parts from Roger Bacon, who has already guessed at the double identity of his friend.
Giordano goes back to France, and quickly to Sens… and at last, in the abbey of Ste.-Colombe he succeeds in getting
hold of Theophilact Simocattas' letters and of one book of the comedies of Plautus; he cannot look for the other
one, before being discovered, and having to escape in a hurry. He goes back to the Maturin monastery, but there
he finds several inquisitors already waiting for him. He leaves two letters with brother Thomas, and flees from
Paris for the last time. But by now he is being pursued without respite.
He stakes his all, trying to outwit his persecutors. He takes the road towards Montségur. In the cave near
Tarascon he copies the Greek pages that are included in the two manuscripts, and then hides the originals in
a crack in the rock. Then he arrives at the foot of the steep hill that is being besieged by an army of more
than ten thousand men, and discovers that by the valley of Le Porteil, where the wall seems quite impossible
to climb, every now and then someone does in fact get in or out of the castle. He gets to the top, with the
help of Guihem Montanhagol (an Occitan poet and patriot), and at last can once more embrace Esclarmonde.
He aims to make numerous copies of the keys of knowledge; and then leave the castle for ever, together with
the girl, to take refuge beyond the Pyrenees, in the hospitable small town of Berga. But Escalrmonde is an
invalid - as well as being blind - and can no longer walk far.
Giordano nonetheless makes many copies of The Path of the Sun, with the revolutionary scientific discoveries that
had come from Armenia in the year 662, and begins to evacuate the precious library of Montségur. But he no longer
tries to escape, being called to a high destiny along with his dear Esclarmonde and the last of the Cathars.
During the months in which the impregnable fortress is being besieged, there is a battle of wits between the
inquisitor Friar Ferrier, who is in command of the crusading army, and Giordano. Friar Ferrier wants to get
his hands not only on the castle and the Cathars, but also on Giordano and the keys of knowledge. The evening
before the surrender four men, each with a copy of The Path of the Sun, climb down the terrible wall and flee.
On the morning of the 16th of March, 1244, a gigantic pyre is built at the foot of Montségur, and more than 210
Cathars are burn alive. Among them, clasped together at the same stake, Esclarmonde's grandmother Marquesia, her
mother Corba, Esclarmonde herself and Giordano. Before consigning them to the flames, Friar Ferrier informs
Giordano that the four fugitives have been taken, and thus all the books and all the copies of The Path of the
Sun, with the keys of knowledge. There will be no scientific revolution. The world will go on following its
well-regulated course. And history will never know who Giordano Nemorario was: his name will be confused with
that of the first great inquisitor in history, Jordanus of Saxony.
Giordano dies, burnt alive together with the people whose struggle he has shared, together with the girl whom
he has loved as if she were his own daughter.
But Friar Ferrier is not victorious. Giordano has given him his body to devour, while Guilhem Montanhagol - with
a copy of the keys of knowledge hidden in his horse's saddle, and disguised as a crusader - leaves Occitania and
rides towards Oxford, to find Roger Bacon. But he is captured shortly before he arrives, and of him no record
Giordano had left one other way open, perhaps the last hope.
The night before the surrender, he had briefed little Perella, the servant-girl in the castle of Montségur, and
friend of Esclarmonde. This brave girl hides herself in a cleft in the rock outside the castle. Then, when the
appalling fire has burnt itself out, and the crusading army have struck their tents, Perella creeps out and
pretending to be a leper makes her way to the cave near Tarascon. There she collects the two precious original
manuscripts, and sets out for a new country, a place in which to lay the foundations for - one day - consigning
the keys of knowledge to someone who shall at last cause them to see the light of day.