Jacques du Chevreul

Jacques du Chevreul (born 1595 in Coutances, France; died 1649 in Paris) was a French mathematician, astronomer, and philosopher.

Du Chevreul grew up in an educated household and was the son of a magistrate. In 1616, he received a Master of Arts for studying humanities and philosophy at the University of Paris. Du Chevreul continued education at a higher level and received a Bachelor of Divinity for theology in 1619. He did not start teaching until 1620 where he remained associated with College Harcourt and University of Paris, up until two years before his death when he taught philosophy at the College Royal. Arithmetica (1622) and Sphaera (1623, 1640, and 1649) were both published in Paris, France. Sphaera, du Chevreul's most popular book was about his view of the world and the universe. He used references from the Bible, Aristotle, and Plato to reject the Copernican model and instead created his own eccentric-epicycle geocentric model of the universe. Du Chevreul believed that the Earth was the center of the universe, but that the major planets Venus and Mercury orbited around the Sun. He theorized that there were wandering and fixed stars in the heavens and there were a total of thirteen planets in his model. The heavens were in the order of the Moon, the Sun (Mercury and Venus orbited around the Sun), Mars, Jupiter surrounded by four Medicean stars, Saturn with two satellites, and above all these levels resided God. Du Chevreul's cosmic scheme is a highly original attempt to resist Copernicanism and accommodate Galileo's telescopic discoveries in an Aristotelian cosmos.

Early life and career Jacques du Chevreul was born 1595 in Cotounces which is a commune in the Manche department in Normandy in north-western France. He was born a year earlier than René Descartes, and died a year before Descartes as well. Unlike Descartes, du Chevreul was always associated with a university, specifically the University of Paris and the College of Harcourt. In the years 1623 through 1626 and 1633 through 1634, du Chevreul taught the Logic and Ethics curriculum.

Several of the chapters corresponded with the four parts:

Chapters 1 and 2 of du Chevreul's book, De definitionibus and De figura mundi, summarize Part 1 of Sacrobosco's Sphere. Chapter 3, De ordine partium, contains mostly new material and covers Copernicus and the Copernican topic of the arrangement of the spheres. Chapters 5 and 7, De circulis coelestibus and De eclipsibus, cover the same topics as Parts II and IV of Sacrobosco's Sphere. Chapter 9, De accidentibus sphaerae, includes sections of Part III, in particular astronomical signs and periods such as days and nights. Du Chevreul notes that Venus and Mercury are placed above the Sun by notable astronomers Plato and Aristotle while astronomers Ptolemy, Regiomontanus, and Sacrobosco placed the planets below the Sun. Jacques du Chevreul believed that the correct placement of Venus and Mercury required an optical instrument, and thus only astronomers of his generation could see that Venus and Mercury orbited the Sun. Du Chevreul's five heavens are, from center to outskirts: 1. The Moon, 2. The Sun, surrounded by the Bourbon stars, Mercury, and Venus, 3. Mars, 4. Jupiter, surrounded by four Medicean stars, and 5. Saturn, with two concentric orbs. The firmament is located above the planetary heavens, with the celestial waters above the heavens and lastly the Empyrean Heaven; both of which are required by the Sacred Scriptures. This consisted of the planetary heaven being liquid and permeable, the solid firmament (or sphere of fixed stars), and lastly the Empyrean. He incorporated the moons of Jupiter and Saturn, the phases of Venus and Mercury, and sunspots into his system while keeping epicycles and eccentrics. While he rejected the Copernican system due to its contradiction to both physics and the Scriptures, he did not reject the arrangement of the Earth and the Moon around the Sun as it was like a terrestrial orb with the Moon contained similarly to an epicycle with the four elements.