The Legacy of Galileo - Keck Institute for Space Studies - Caltech

Creator 5 . Consequently, the results obtained from the observation of the physical world,
which was designed to work perfectly regardless of whether it could be easily comprehended
by humans, in case of conflict must override, if properly validated by sensible experience, the
literal explanation of the Scriptures, which had been conceived taking into account the
limitations of the human mind. Galileo expresses this concept in a famous letter to Duchess
Madama Cristina of Lorraine, wife of his sponsor the Duke of Florence, while defending
himself from the accusation of heresy in affirming that the Earth was revolving around the
Sun:
Being then that the Bible in many instances must be interpreted differently from the
apparent literal meaning of the words, I believe that in debates about Nature the
Bible’s explanation should be the last resort… Being Nature inexorable and immutable
and not caring whether its inner laws and methods of operation are understandable to
men, for this reason it never transgresses its governing rules… Hence, it appears that
no physical manifestation which the experience of sense sets before our eyes, or
which necessary demonstrations prove to us, ought to be questioned (much less
condemned) based upon biblical references whose words might appear to be leading
to a different conclusion. For the Bible is not constrained in every expression to
conditions as strict as those governing all natural effects. 6
Paradigms were changing In medicine also; anticipating the changes occurring in physics, the
great Andreas von Wesel (Vesalius), had demonstrated at the beginning of the second half of
the 16th century that the human anatomical structure was very different from that described
by the Greek authors of medical treatises, and before him, although with different intentions,
Leonardo Da Vinci had faithfully represented the details of the human body by observing and
dissecting corpses in the morgue of the Florentine hospitals, against the rules of piety
imposed by the Church. In Pisa, the great naturalist Andrea Cesalpino, some years before
William Harvey, performed experiments on the blood circulation, being able to demonstrate
that venous blood was moving back to the heart, contradicting what Aristotle had affirmed.
Galileo describes this conflict between experience and the Aristotelian doctrine in the
Dialogue Concerning the Two Chief World Systems, narrating an episode that he would have
witnessed in Venice:
One day I was in Venice at the house of a famous
 physician, where some flocked for
their studies, while others sometimes went out of curiosity to witness anatomical
dissections… By chance
 that day, when I was there, he was in search of the origin
and
 stem of the nerves…The anatomist showed how the great bundle of
 nerves,
departing from the brain, their root, passed by the nape of the
 neck, further
extending… while only a very small filament, as fine as a
 thread, arrived at the heart.
Then he turned to a gentleman in the audience whom he knew to be a Peripatetic
philosopher… and asked if he was satisfied and persuaded that the origin of the
nerves was in the brain and not in the heart. The philosopher answered: “You have
5
Kenneth J. Howell God’s Two Books (University of Notre Dame Press, Notre Dame 2002)
6
Galilei, G. Lettera a madama Cristina di Lorena GG, V, p 316 (translation by Cinzia Zuffada)
4