Answer:
On 31 October 1517, as legend has it, renegade monk Martin Luther nailed a document to the door of All Saints' Church in Wittenberg, Germany. The Ninety-five Theses marked the beginning of the Reformation, the first major break in the unity of Christianity since 1054. Luther proclaimed a radical new theology: salvation by faith alone, the priesthood of all believers, the ultimate authority not of the Church, but of the Bible. By 1520, he had rejected the authority of the pope. Lutherans and followers of French reformer John Calvin found themselves engaged in bitter wars against Catholicism that lasted for a century and a half.
This age of religious warfare was also the age of the scientific revolution: Nicolaus Copernicus's On the Revolutions of the Celestial Spheres (1543), Tycho Brahe's Introduction to the New Astronomy (1588), Johannes Kepler's New Astronomy (1609), Galileo Galilei's telescopic discoveries (1610), the experiments with air pressure and the vacuum by Blaise Pascal (1648) and Robert Boyle (1660), and Isaac Newton's Principia (1687).
Were the Reformation and this revolution merely coincident, or did the Reformation somehow facilitate or foster the new science, which rejected traditional authorities such as Aristotle and relied on experiments and empirical information? Suppose Martin Luther had never existed; suppose the Reformation had never taken place. Would the history of science have been fundamentally different? Would there have been no scientific revolution? Would we still be living in the world of the horse and cart, the quill pen and the matchlock firearm? Can we imagine a Catholic Newton, or is Newton's Protestantism somehow fundamental to his science?
The key book on this subject was published in 1938 by Robert Merton, the great US sociologist who went on to invent terms that have become part of everyday speech, such as 'role model', 'unanticipated consequence' and 'self-fulfilling prophecy'. Merton's first book, Science, Technology and Society in Seventeenth-Century England, attracted little attention initially. But in the 1960s, 1970s and 1980s, historians of science endlessly and inconclusively debated what they called the Merton thesis: that Puritanism, the religion of the founders of the New England colonies, had fostered scientific enquiry, and that this was precisely why England, where the religion had motivated a civil war, had a central role in the construction of modern science.
Those debates have fallen quiet. But it is still widely argued by historians of science that the Protestant religion and the new science were inextricably intertwined, as Protestantism turned away from the spirituality of Catholicism and fostered a practical engagement with the world, exemplified in the idea that a person's occupation was their vocation. Merton was following in the footsteps of German sociologist Max Weber, who argued that Protestantism had led to capitalism.
I disagree. First, plenty of great sixteenth- and seventeenth-century scientists were Catholics, including Copernicus, Galileo and Pascal. Second, one of the most striking features of the new science was how easily it passed back and forth between Catholics and Protestants. At the height of the religious wars, two Protestant astronomers were appointed one after another as mathematicians to the Catholic Holy Roman Emperor: first Brahe, then Kepler. Louis XIV, who expelled the Protestants from France in 1685, had previously hired Protestants such as Christiaan Huygens for his Academy of Sciences. The experiments of Pascal, a devout Catholic, were quickly copied in England by the devoutly Protestant Boyle. The Catholic Church banned Copernicanism, but was quick to change its mind in the light of Newton's discoveries. And third, if we can point to Protestant communities that seem to have produced more than their share of great scientists, we can also point to Protestant societies where the new science did not flourish until later — Scotland, for example.
Discovery and dissemination
What made the scientific revolution possible were three developments. A new confidence in the possibility of discovery was the first: there was no word for discovery in European languages before exploration uncovered the Americas. The printing press was the second. It brought about an information revolution: instead of commenting on a few canonical texts, intellectuals learnt to navigate whole libraries of information. In the process, they invented the modern idea of the fact — reliable information that could be checked and tested. Finally, there was the new claim by mathematicians to be better at understanding the world than philosophers, a claim that was grounded in their development of the experimental method.