Senses Vs. Paper

Galileo Galilei, Discorso al Serenissimo Don Cosimo II … intorno alle cose, che stanno sù l’Acqua, ò che in quella si muovono … Bound together with two counter-papers by other authors.

Printed in Bologna in 1655 at Dozza.

The Catholic Church needed more than 300 years to make its peace with Galileo Galilei. Galilei wasn’t the first to oppose the ecclesiastical world view. However, until today we see him as someone who followed the path of reason and remained true to his convictions, even though it might contradict the prevailing opinion. We have to keep in mind that Galilei actually was a devout Catholic, and like Luther he wanted to reform, not to divide. But first of all, he wanted to do research. And while doing so, at first he didn’t get into conflict with the Church but with believers of a completely different kind: Aristotelians. A print of 1655, which contains a famous work of Galilei and two reactions, bears witness to this conflict of scholars. Thus, we’ll immediately enter the scholarly discourse of 1612…

In 1609 Galilei wrote a letter to the Doge of Venice offering him a telescope that he had built: for observing the enemy. However, a draft of the letter demonstrates that the scientist had long realised what could actually be done with the instrument: observing the sky. The “spots” on the lower part represent the positions of the “Galilean moons”.

Court Mathematician and Astronomer

Galileo Galilei’s story of success started in 1610. One year earlier, he had learned of a highly modern invention that was to change his life. Some Jan Lippershey had mounted lenses in a tube, one behind the other – the first telescope. The rulers were happy about it because it could be used in war for observing the enemy. Galilei built such a device for himself and immediately understood its revolutionary possibility of observing heavenly bodies. When he discovered the four moons of Jupiter, which cannot be seen with the bare eye, his new contract was already home and dry. He left his position at the University of Padua to work at the Medici court in Florence and flattered his new masters by giving the newly discovered moons the sonorous name of “Medician stars” (nevertheless, they are known as “Galilean moons” today).

A painting by Justus Sustermans depicts Galileo Galilei as an old man.

He had quite a reason to be thankful: as court mathematician, court philosopher and professor of mathematics in Pisa without teaching duties, the genius enjoyed absolute freedom of research. He was particularly fascinated by astronomical studies, and constantly improved his telescope. His observations were doubted by many, partly because the quality of telescopes still varied greatly. Legend has it, that Galilei’s colleagues even refused to look through his telescope! His moons had caused a sensation because they were the first celestial bodies that didn’t revolve around the earth. In 1611 Galilei presented his instrument to the Jesuits in the Vatican. Back then, they were considered the highest scientific authority. They checked Galilei’s observations and confirmed them. Now Galileo could focus on a completely different battle…


Mathematics Against Logics, Senses Against Paper

Scholasticism was still considered the school of thought that provided the world view in line with the doctrine of the Church. This medieval education was based primarily on the works of Greek philosopher and researcher Aristotle. According to their stylite, many thinkers referred to themselves as scholars of the Aristotelian or Peripatetic school of thought and, by then, they were more faithful to the letters of his work than to the actual questions they were supposed to answer. These philosophers thought they could explain the world with propositional logic alone. They overlooked the fact that Aristotle himself hadn’t been a stay-at-home out of touch with reality at all. Because of their rigid beliefs, many of them found the master’s words as sacrosanct as the words of the Bible. Thus, Aristotelians were convinced that objects didn’t float on water because of their specific weight but because of their shape as Aristotle once had declared. However, just one generation after Aristotle, Greek scholar Archimedes had already discovered the truth about that matter. (Remember the bath tub and him proclaiming “Eureka!”.)

You might think that the issue could easily be clarified by means of experiments, however, experiment weren’t popular among these scholars. And then a hothead like Galilei, armed with his authority, busted in the conversation and wrote in 1612 a paper about “the things that float on water”. By means of mathematical drawings, he presented a clear demonstration of why Aristotle was wrong – and turned the Aristotle believers against him.

Of course, this paper had to be countered. Especially two Aristotelians felt a vocation to write counter-papers: Florence philosopher Lodovico delle Colombe and Vincenzo M. Di Grazia. Their essays are extremely eloquent and one name appears particularly often: Aristotle. For the two of them weren’t eager to prove how things actually were, but that Aristotle was right, that he was infallible and couldn’t be contradicted. Today, this is difficult to understand and doesn’t really correspond to our concept of science.

Galilei dryly remarked in a later writing: “Only the blind need a guide in open and flat land. Study Aristotle, but don’t make yourself complete prisoners of his authority. Argue with reason, not with texts and authorities, for we are dealing with the world of our senses, not with a world of paper.”

By the way, Galilei appreciated many of Aristotle’s approaches and discoveries, too. Nevertheless he was a young “maverick”, a modern scientist that didn’t just read and believed but questioned and verified. After all, that’s what Aristotle had done as well.

In the Palazzo Pitti in Florence, Galileo Galilei refuted his opponents in a very practical way: by means of an experiment. Photo: Stefan Bauer / CC BY-SA 2.5

A Testimony to an (Un-)Scientific Discourse

Galilei realised that this rather superfluous discourse couldn’t be ended by replying to the Aristotelian papers, but only by presenting irrefutable evidence. On 2 October 1612, Galilei’s employer, the Grand Duke of Tuscany, invited Cosimo II to witness an experiment at the Palazzo Pitti in Florence. Since Galilei had dedicated his work “On Floating Bodies” to the Grand Duke, his honour was at stake, too. In a practical demonstration, Galileo proved that his statements weren’t based on philosophical quibbles or senseless battles on paper, but on provable scientific findings: a victory of the senses over paper! End of discussion. Today, we know almost nothing about Galilei’s two opponents.

Around the middle of the 17th century, and thus about 10 years after Galilei’s death, Bologna printer Dozza published various papers by Galilei, including a two-volume edition of his works. In this issue, the treatises were paginated individually, and clients could order a costumed edition of Galilei’s works. For our edition, Dozza apparently thought it would make sense to emphasise the true genius of the polymath by combining the treatise “On Floating Bodies” (from the second edition of the complete edition) with the Aristotelian reactions, which didn’t have much scientific content. Even if the supremacy of Galilei’s arguments is obvious for us today, this edition demonstrates how sensitive people were regarding the scientific discourse around 1650. After all, Galilei had mentioned in the preface of this work another highly controversial discovery he made thanks to his telescope: sunspots. And it was these sunspots which distanced him more and more from the scientific positions accepted by the Church.