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Morin, Jean-Baptiste


(b. Villefranche, Beaujolais, France, 23 February 1583; d. Paris, France, 6 November 1656)

medicine, astronomy, astrology.

Morin was a strange person but typical of his age in that he undertook very varied activities. He was sufficiently successful and intelligent to acquire a reputation in his own time, but he failed to demand of himself the thorough discipline that would have enabled him to produce truly scientific work. A medical doctor at first, he then took an interest in all the topics associated with hermetic literature. In order to penetrate the mysteries of nature he studied mining and astrology (he was later to draw up an astrological chart for the infant Louis XIV). His talents won him the support of influential people, and in 1630 he was professor of mathematics at the Collège Royal (now Collège de France), a position he held until his death.

A polemicist by disposition, he quickly sought to distinguish himself in the major debates most likely to bring him widest attention. In 1624 he published a defense of Aristotle in conjunction with the refutation of the theses of Antoine de Villon and of étienne de Claves, both of which had been condemned by the Sorbonne. He opposed Galileo before and after the trial of 1633. He attacked Descartes in 1638, flattering himself that he had detected how bad his philosophy was from the moment that they had met, before Descartes’s departure for Holland.

If Morin suffered injustice in the judgments reached by his contemporaries, especially Boulliau, he owed his poor reputation to the way in which he conducted his disputes. This fault is best illustrated in the matter of the determination of longitudes. During the very period when he was presenting himself as the champion of the immobility of the earth, Morin simultaneously wished to prove that he was capable of drawing inspiration from Kepler, of correcting the Rudolphine Tables, and of proposing a method for finding longitudes that would always be usable at sea and sufficiently precise for navigation. The only original thing about this method, which was based on the observation of the moon, was its claim of utilizing the movements of the moon relative to the stars as a universal clock and of generalizing this phenomenon to calculate the difference in hours between two positions on the earth. The method required new observational instruments, which could be used with sufficient precision on ships, the improvement of the mathematical solution of spherical triangles, and the possibility of a systematic checking of tables of lunar motion established for a given position. Morin glimpsed these three facets of the problem and made an important contribution to instrumental technique by utilizing telescopes for the sights and verniers for the measurement of angles; but he was incapable of mastering the complex problem of precision in a process involving both observation and computation. Ambition and the desire to obtain a pension from Richelieu made him deaf to all objections.

From 1626 to 1628 Morin undertook research in optics with the engineer Ferrier, in whom Descartes had placed his hopes. Shortly afterward his friendships with Peiresc and Gassendi helped him in observational astronomy. But the affair of the longitudes, with the prolonged debate (1634-1639) that put him in opposition to Étienne Pascal, Mydorge, and Beaugrand, alienated the scientific community, and he continued his work largely in isolation.

Morin’s posthumously published Astrologia gallica reveals that he had interesting ideas concerning the theory of heat and the temperature of mixtures. Moreover, in the correspondence of Mersenne and Descartes references to Morin are not entirely negative. Despite his undoubted talents, Morin’s philosophical and scientific choices were too often political ones and prevented him from producing the caliber of work of wihch we now see he was capable.


I. Original Works. For works of Morin see Astronomicarum domorum cabala detecta (Paris, 1623); Refutation des thèses … d’A. Villon et E. de Claves … contre les doctrines d’ Aristote (Paris, 1624); Famosi et antiqui problematis de telluris motu vel quiete hactenus optata solutio (Paris, 1631); Trigonometriae canonicae libri tres quibus planorum et sphaericorum triangulorum theoria … adjungitur liber quartus pro calculi tabulis logarithmorum (Paris, 1633); Pro telluris quiete (Paris, 1634); Astronomia jam a fundamentis integre et exacte restituta … (Paris, 1640); La science des longitudes… (Paris, 1647); and Astrologia gallica … (The Hague, 1661), published posthumously under the auspices of Marie Louise of Gonzaga, queen of Poland, which also contains a Latin trans. of the anonymous Vie de Morin (1660), the French original of which is lost.

II. Secondary Literature. For information about Morin see P. Bayle, Dictionnaire historique et critique, II, pt.1 (Rotterdam, 1697), 602–612; M. Delambre, Histoire de l’astronomie moderne, (Paris, 1821), 236–273; G. de Fouchy, “Sur la date de l’application des lunettes aux instruments d’observation …,” in Mèmoires de l’Académie royale des sciences pour l’année 1783 (1787), 385–392; L. Moreri, Le grand dictionnaire historique, VII (Paris, 1759), 786–788; and J. Montucla, Histoire des mathématiques (Paris, 1799), II, 336–1802; IV, 543–545.

Pierre Costabel

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"Morin, Jean-Baptiste." Complete Dictionary of Scientific Biography. . 26 Jun. 2017 <>.

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Morin, Jean-Baptiste (1583-1656)

Morin, Jean-Baptiste (1583-1656)

Jean-Baptiste Morin, French physician, mathematician and the leading astrologer of the seventeenth century, was born in Villefranche on February 23, 1583. Morin studied at Avignon, where he received his medical degree and began a career as a physician. However, astrology fascinated him, and he secured a position as astrologer to the duke of Luxembourg and later the duke d'Effiat. Then in 1830 the king of France offered him the chair in mathematics at the College of France, and Morin moved to Paris, where he remained for the rest of his life.

While formally a professor of mathematics, he also functioned as court astrologer. As such he was present in the group witnessing the birth of Louis XIV in 1638. He served Cardinal Richelieu (who is noted to have disliked Morin personally but was respectful of his knowledge) and Cardinal Mazarin.

He would be the last of the outstanding French astrologers prior to the modern era, as astrology was on the wane under the attack of the new science. However, he was able to make a number of contributions to the modernizing of astrology, a necessity to prevent its being completely stamped out. Morin developed a system of division of the astrological houses, now called the Morinean system, based upon the equal division of the equator, which is then projected onto an ecliptic as means of handling the elliptical orbit of the earth.

During his life Morin published little. His major work, the Astrologia Gallica, was published in Latin in 1661, five years after his death. It was largely unread except by a few intellectuals until 1897, when a French translation was finally published. Thus the work informed the pioneers of the French phase of the modern astrological revival. Morin died in Paris on November 6, 1656.


Brau, Jean-Louis, Helen Weaver, and Allan Edmands. Larousse Encyclopedia of Astrology. New York: New American Library, 1977.

Morin, Jean-Baptiste. Astrologia Gallica. The Hague, Netherlands, 1661.

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