Pierre Gassendi, a French philosopher, born at Champtercier, Provence, Jan. 22, 1592, died in Paris, Oct. 24, 1655. After having studied philosophy at Aix, he was appointed at the age of 16 professor of rhetoric at Digne. When 20 years of age he was simultaneously elected to the two chairs of philosophy and theology at Aix, of which he chose the latter. While in this office his leisure was employed in the study of anatomy, astronomy, and even astrology, a science which he afterward condemned as a delusion. He resigned his professorship in 1623. In 1624 he published at Grenoble the Exercitationes Paradoxical adversus Aristote-loeos, in which he was the first to point the distinction between the church and the scholastic philosophy. He designed to complete the work in five books, but only two were ever written. About the same time he was appointed provost of the cathedral at Digne, but the appointment was contested, and was not confirmed until ten years later. Meanwhile he travelled for a time, and entered into correspondence with Galileo, to whom he expressed his concurrence with the Copernican system.

Returning to Digne, he continued his ecclesiastical duties, and in 1630 wrote a treatise against the mystical and alchemistic doctrines of Robert Fludd. He was a constant correspondent of Kepler, who before his death had publicly announced that Mercury and Venus would pass over the disk of the sun on Nov. 7, 1631. Gassendi was the first to observe the passage of Mercury, and wrote a minute account of the phenomenon. On the appearance of the Discours de lamethode and the Meditations of Descartes, a controversy arose between the two philosophers. The daring and original genius of Descartes was in striking contrast with the erudition and critical acumen of his opponent, who excelled him in caution and courtesy. In 1645 Gassendi received from Cardinal Richelieu the appointment of mathematical professor in the royal college of France; and two years later he published at Lyons his biographical treatise, De Vita, Moribus et Placitis Epicuri, which was followed by his Syntagma Philosophiw Epicurean (Lyons, 1649). They form together a complete review of the life, eulogy of the character, and reconstruction of the philosophical system of Epicurus. The Epicurean ethics and physical theory of atoms and a vacuum are elaborately vindicated, and conformed to the principles of Christianity and the discoveries of modern science.

His feeble health obliged him to resign his professorship, and he retired to Toulon, where he was occupied for two years with the preparation of another great philosophical work. In 1653 he returned to Paris, and there completed the work, the Syntagma Philosoplricum, an encyclopaedic view of the entire circle of science, and the most complete and learned statement of his opinions. It was not published until after his death, and forms the first two volumes of his complete works, edited by Montmor and Sor-biere (6 vols., Lyons, 1658). It is divided into three parts, logic, physics, and ethics, is elaborated with great learning and minuteness of criticism, and contains an eclectic philosophy formed by the union of ideas borrowed from various schools rather than a new system. His system is akin to that of Locke rather than of the French followers of Locke, and even a part of his phraseology, as the actiones reflexivae, anticipates that of the Essay on the Human Understanding." It does not appear, however, that Locke was acquainted with his writings. Not only as a metaphysician, but as an astronomer, geometer, anatomist, Hellenist, historian, and elegant writer, Gassendi merits distinction.

He was the personal friend of most of the learned men of his time, the first disciple in France of Bacon, and the precursor of Newton. The aurora borealis, the parhelia, the conjunctions of Venus and Mercury, the occupations of the satellites of Jupiter, and the properties of the magnetic needle were among the subjects of his researches. He wrote the lives of the principal astronomers of his age, and in the preface gave a brief and admirable history of astronomy. By those who knew him he was beloved for his amiability and modesty. The latest complete edition of his works is that edited by Averrani (6 vols., Florence, 1728). An abridgment by Bernier (Paris, 1678) has been several times republished. His life has been written by Sorbiere (for the first edition of his collected writings, Lyons, 1658), and by Bou-gerel (Paris, 1637).