Astrology today is often seen as the epitome of pseudoscience. Yet, until the 17th century, it was considered a legitimate scholarly discipline, serving as the practical branch of astronomy. It was taught at universities and applied in fields as varied as medicine (as a diagnostic and prognostic tool), agriculture, and navigation. Starting in the 15th century, however, astrology began to lose its status and was gradually pushed to the margins of scholarly recognition and intellectual life. The reasons behind this decline, and the triggers that set the process in motion, remain an intriguing question for historians of early modern science.

This question not only seeks to explain astrology’s marginalization but also raises issues about the methodological lenses used to analyze it. Was the decline driven by changing attitudes among ruling and social elites? Or was it the result of intellectual developments within the scientific community-or perhaps a combination of both?

Exploring the Decline Through Jean-Baptiste Morin

To address these questions while bridging sociological and intellectual perspectives, this article focuses on the career of Jean-Baptiste Morin (1583–1656), a French mathematician often regarded as the “last official astrologer.” Morin’s trajectory illustrates how astrology’s fortunes were tied to the attitudes of the French ruling class and key figures at court. Early in his career, Morin enjoyed widespread recognition and esteem. His appointment to the chair of mathematics at the Collège Royal in 1629 was not an isolated event but reflected the cultural politics of France’s ruling elites-from Cardinal Bérulle to Cardinal Richelieu-who believed in astrology’s legitimacy. These elites turned to Morin for politically significant consultations, while his theoretical work reinforced and legitimized their belief system.

Morin’s Downfall: Intellectual and Political Shifts

The article then turns to Morin’s eventual downfall, focusing on his polemic with Pierre Gassendi (1592-1655) and his circle. This dispute, initiated by Morin to challenge Gassendi’s support of Copernicanism, soon escalated into a broader critique of astrology. Many historians have viewed this conflict as an intellectual turning point, driven by scientific reasoning and motives. However, this narrative overlooks the strong political undercurrents of the time.

As the paper reveals, the polemic unfolded against the backdrop of the Fronde, a period of civil unrest in France, and was deeply shaped by political motives. At the time, Morin was aligned with Cardinal Mazarin, who had been temporarily ousted from power, while Gassendi was connected to Louis de Valois, Comte d’Alais (1593-1653), the governor of Provence and a prominent supporter of the anti-Mazarin faction. What is more, Cardinal Mazarin’s apparent reluctance to defend Morin’s interests at the time of his return to power is telling. It reflects a growing unease among French elites about the public association between astrology and politics, coupled with their increasing disengagement from astrology as a discipline.

The Role of Politics in Astrology’s Decline

This analysis argues that astrology’s decline in France cannot be attributed solely to “learned jurisdiction” or intellectual debates. The shifting cultural and political priorities of the ruling classes played a crucial role. The story of astrology’s marginalization in 17th-century France highlights the intricate interplay between intellectual developments and political dynamics. Through the lens of Jean-Baptiste Morin’s career, we see how cultural and political shifts contributed to astrology’s decline, reshaping the boundaries of legitimate knowledge in early modern Europe.

Patronage, cultural politics and the marginalization of astrology in seventeenth-century France: the case of J.-B. Morin and of his polemics with Pierre Gassendi and his circle by Rodolfo Garau