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Honoré Fabri

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5 April 1607

Virieu-le-Grand, Dauphiné, France

8 March 1688

Rome, Italy

Honoré Fabri entered the Jesuit Order in 1626 spending two years at Avignon. In 1628 he entered the Collège de la Trinité in Lyon where he studied philosophy, going on to study theology at Lyon from 1632 to 1636. He was ordained in 1635.

His first position was in a Jesuit college, namely as professor of philosophy in Arles from 1636 to 1638. Further positions in Jesuit colleges followed. He was professor of logic in Aix- en- Provence for a year from 1638 then, for six years from 1640, professor of logic and mathematics at the Collège de la Trinité in Lyon.

In 1646 Fabri went to Rome where he met Ricci . He joined the Penitentiary College being involved with the Inquisition. He was unable to avoid religious problems himself and he was accused of believing the philosophy of Descartes . After spending a year back in France in 1668/69 he returned to Rome and was put in prison. Through Ricci he had made the acquaintance of Grand Duke Leopold II and the Grand Duke saw that Fabri was released fairly soon from prison.

Fabri worked on astronomy, physics and mathematics. He studied Saturn's rings in 1660, a topic on which he became involved in a dispute with Huygens which ran for five years. He also discovered the Andromeda nebula. Fabri developed a theory of tides which was based on the action of the moon. He also studied magnetism, optics and calculus.

In calculus he was closer to Newton than to Cavalieri and his notation was cumbersome. His work on the calculus appeared in his major mathematical publication Opusculum geometricum. This book was written because of the controversy about the cycloid which arose from Pascal 's challenge. In this work Fabri computed

xnsin x dx, sinnx dx

and other integrals. He had a major influence on the development of the calculus through Leibniz .

Fabri's students include Cassini and La Hire at the Collège de la Trinité and he also worked with Dechales . He was a friend and correspondent of Gassendi whom he first met while he was at Aix-en-Provence and he also corresponded with Huygens , Leibniz , Descartes , Mersenne and others.

Source:School of Mathematics and Statistics University of St Andrews, Scotland