Galileo is still causing controversy centuries after his death. It is being argued that many of his radical advances weren't quite so radical. There shouldn't be much controversy in discovering that Galileo did what modern scientists do, build on others work. Historians of science have largely accepted this for decades. The only controversy is what took historians so long. The natural philosophers who started the calculatory tradition and the modern study of dynamics were amongst the most famous natural philosophers in the middle ages. It doesn't seem that his debt to his predecessors would have been difficult to identify...if scholars wanted to look. Scholars study what can be published. That is why George Sarton, the editor of Isis, may hold the key to understanding this delay. Isis was the most important journal of the history of science in the early twentieth century.
The medieval natural philosophers who applied mathematics to the study of motion are known as the "Calculatores" (see The Calculatores). Some were very famous. Thomas Bradwardine was mentioned in Geoffrey Chaucer's Canterbury Tales. The calculatory tradition was widely discussed and taught throughout Europe. The map below shows universities that were active in 1614 (modified from here). The dark squares mark universities where professors considered 'calculators' are known to have taught or hold high administrative positions. The Calculatores made notable progress in the study of dynamics. Domingo de Soto published a Law of Free Fall consistent with Galileo's shortly before Galileo was born. The Mean Speed Theorem,often attributed to Galileo, was actually derived by Calculatores three centuries before Galileo. Even though they left a paper trail of manuscripts and references, they were rarely mentioned in historical journals of the early 20th century.
To understand why early historians skipped over the 'Calculators' we might look to the one historian of science from the time who did attempt a serious scholarly study of their work, Pierre Duhem. Pierre Duhem either did not know or did not care that what he was doing was career suicide. At the time, the history of science as a separate discipline was a new idea and the community studying the history of science was very small. The community on both sides of the Atlantic was dominated by secularists with negative views on the influence of the church. George Sarton was one of these secularists. Duhem's work could force a rethink of both the importance of the Middle Ages and the role of church. Almost all of the Calculatores were Roman Catholic clergy.
Pierre Duhem was a rare genius. A century after his death, his work is referenced in three different disciplines; thermodynamics, philosophy of science and the history of science. Duhem switched focus to the history of science after establishing an international reputation in physics. Duhem started with books on the history of statics and mechanics, which were followed by several on Leonardo da Vinci. It was his study of Leonardo that would eventually lead him into trouble. Following the chain from da Vinci to his predecessors in the fourteenth century, Duhem landed on medieval philosophers who were proposing concepts and laws credited to the scientists of the seventeenth century. When Duhem started his studies, he believed in the "Dark Age Myth", like his contemporaries. Now he didn't.
The success of Pierre Duhem's texts in physics and the history of science set him up for an iron-clad contract with A. Herman to publish the monumental 10-volume Le System du Monde, a history of cosmology from Greek times through to Copernicus. Duhem sent the first volume, dealing primarily with Greek science, to George Sarton to be reviewed for his journal, Isis. George Sarton gave it a positive review and let Duhem know that he was looking forward to future volumes. Isis did not review any of the subsequent volumes of the System du Monde. Duhem's work was rarely cited in Isis over the next 40 years (see Sarton: The Isis Files). The iron-clad publishing contract with A. Hermann suddenly wasn't iron-clad. A. Hermann reneged on the contract after 5 volumes were published. Pierre Duhem died in 1916, soon after completing the manuscripts for the last five volumes. Hermann and Cie. did finally publish the final manuscripts, but in 1954, and only after Louis de Broglie, the Nobel Prize winning physicist, threatened a lawsuit if they didn't.
We know why A. Hermann wouldn't publish the final manuscripts. It was censorship. Abel Rey, the head of the Institute d'Histoire des Sciences at the Sorbonne, admitted as much. Abel Rey's source was the management of Hermann et Cie. They were being pressured by highly placed members of the French scientific community not to publish his final manuscripts. Duhem had already hinted at the importance of the Calculatores and Parisian doctors in the first 5 volumes but the later volumes presented an intensive treatment of their work. His theories on the relative importance of the church in the development of science are still argued today. More problematic than his theories were his facts. If the mean speed theorem and the times square law were being widely discussed in medieval Europe that was a problem. If medieval philosophers were discussing motion in terms remarkably close to those used by seventeenth century scientists that was a problem. And if Duhem had documentary proof of Galileo's debt to the Calculatores that was a problem.
Stanley Jaki, an historian of science, believes that George Sarton played an important role in the censorship of Duhem's work. George Sarton was the editor of the most important journal of the history of science. Editors and referees act as gatekeepers who decide who and what is important in a field. This is especially true in a young discipline with very few reputable journals. Sarton, as gatekeeper, had both ideological and professional reasons to be critical of Duhem.
George Sarton had an almost religious admiration for the good of science. This extreme view of science is now called Scientism. He once wrote: "The history of science is the only history which can illustrate the progress of mankind". His negative opinion of the church was almost as extreme. As late as 1955, Sarton was still praising The History of Warfare of Science with Theology [_1_] . This was a virulently anti-Catholic and anti-Christian history of science and the church. It argued for the inherent conflict of church and science. It is surprising that a historian would be recommending such a flawed book long after it had been discredited. The books 'facts' were sometimes drawn from popular historical fictions. Pierre Duhem's work challenged the conflict thesis that Sarton seemed so comfortable with.
After Duhem's death, George Sarton continued his central role in nurturing the "history of science" as an independent discipline. This included his own teaching at Harvard, his personal research and editing Isis, the most important history of science journal of the time. His editorial record at Isis does raise some issues. These are discussed in more detail at Sarton: The Isis Files. Considering the important works Duhem had completed on the history of statics, Leonardo da Vinci, Greek science, and medieval dynamics, it is odd that Duhem was referenced so rarely during Sarton's editorship. Sarton allowed publication of an article by one of his graduate students that attacked Pierre Duhem on a personal level [_2_] . Any reference to a Calculatore was extremely rare [_3_] .