Comets, a Manifesto, and a Dialogue

In Florence again, Galileo was ill and depressed during much of 1617 and 1618.
He did not have the strength to comment when three comets appeared in the
night sky during the last four months of 1618. He was stirred to action, however,
when Father Horatio Grassi, a mathematics professor at the Collegio Romano and
a gifted scholar, published a book in which he argued that the comets provided
fresh evidence against the Copernican cosmology. At first Galileo was too weak
to respond himself, so he assigned the task to one of his disciples, Mario Guiducci,
a lawyer and graduate of the Collegio Romano. A pamphlet, Discourse on
Comets, was published under Guiducci’s name, although the arguments were
clearly those of Galileo.
This brought a worthy response from Grassi, and in 1621 and 1622 Galileo
was sufficiently provoked and healthy to publish his eloquent manifesto, The
Assayer. Here Galileo proclaimed, “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 to read the
alphabet in which it is composed. It is written in the language of mathematicsand its characters are triangles, circles and other geometric figures, without
which it is humanly impossible to understand a single word of it; without these,
one wanders about in a dark labyrinth.”
The Assayer received Vatican approval, and Cardinal Barberini, who had supported
Galileo in his debate with della Colombe, wrote in a friendly and reassuring
letter, “We are ready to serve you always.” As it turned out, Barberini’s
good wishes could hardly have been more opportune. In 1623, he was elected
pope and took the name Urban VIII.
After recovering from a winter of poor health, Galileo again traveled to Rome
in the spring of 1624. He now went bearing microscopes. The original microscope
design, like that of the telescope, had come from Holland, but Galileo had greatly
improved the instrument for scientific uses. Particularly astonishing to the Roman
cognoscenti were magnified images of insects.
Shortly after his arrival in Rome, Galileo had an audience with the recently
elected Urban VIII. Expecting the former Cardinal Barberini again to promise
support, Galileo found to his dismay a different persona. The new pope was
autocratic, given to nepotism, long-winded, and obsessed with military campaigns.
Nevertheless, Galileo left Rome convinced that he still had a clear path.
In a letter to Cesi he wrote, “On the question of Copernicus His Holiness said
that the Holy Church had not condemned, nor would condemn his opinions as
heretical, but only rash. So long as it is not demonstrated as true, it need not be
feared.”
Galileo’s strategy now was to present his arguments hypothetically, without
claiming absolute truth. His literary device was the dialogue. He created three
characters who would debate the merits of the Copernican and Aristotelian systems,
but ostensibly the debate would have no resolution. Two of the characters
were named in affectionate memory of his Florentine and Venetian friends, Gianfrancesco
Sagredo and Filippo Salviati, who had both died. In the dialogue Salviati
speaks for Galileo, and Sagredo as an intelligent layman. The third character
is an Aristotelian, and in Galileo’s hands earns his name, Simplicio.
The dialogue, with the full title Dialogue Concerning the Two Chief World
Systems, occupied Galileo intermittently for five years, between 1624 and 1629.
Finally, in 1629, it was ready for publication and Galileo traveled to Rome to
expedite approval by the Church. He met with Urban and came away convinced
that there were no serious obstacles.
Then came some alarming developments. First, Cesi died. Galileo had hoped
to have his Dialogue published by Cesi’s Academy of Lynxes, and had counted
on Cesi as his surrogate in Rome. Now with the death of Cesi, Galileo did not
know where to turn. Even more alarming was an urgent letter from Castelli advising
him to publish the Dialogue as soon as possible in Florence. Galileo
agreed, partly because at the time Rome and Florence were isolated by an epidemic
of bubonic plague. In the midst of the plague, Galileo found a printer in
Florence, and the printing was accomplished. But approval by the Church was
not granted for two years, and when the Dialogue was finally published it contained
a preface and conclusion written by the Roman Inquisitor. At first, the
book found a sympathetic audience. Readers were impressed by Galileo’s accomplished
use of the dialogue form, and they found the dramatis personae, even
the satirical Simplicio, entertaining.
In August 1632, Galileo’s publisher received an order from the Inquisition to
cease printing and selling the book. Behind this sudden move was the wrath ofUrban, who was not amused by the clever arguments of Salviati and Sagredo,
and the feeble responses of Simplicio. He even detected in the words of Simplicio
some of his own views. Urban appointed a committee headed by his nephew,
Cardinal Francesco Barberini, to review the book. In September, the committee
reported to Urban and the matter was handed over to the Inquisition.