GASSENDI, PIERRE

Philosopher whose works influenced the growth of mechanics and theoretical astronomy from galileo to Newton; b. Champtercier, Jan. 22, 1592; d. Paris, Oct. 24, 1655.

Exposed to, but not convinced by, the Aristotelianism presented during his student days at the University of Aix (1609–12), the philosophically hungry Gassendi taught rhetoric in the college at Digne. In 1614 he received minor clerical orders, was granted a doctorate in theology by the University of Avignon, and was elected canon-theologian of the cathedral chapter at Digne. In 1616 Gassendi joined the philosophical faculty of the Royal Bourbon College at Aix and was ordained a priest at Marseilles. Gassendi's courses at Aix were ambiguous, for he countered each presentation of an "official" Aristotelian thesis with objections calculated to weaken, if not destroy, its acceptability. When in 1621 the Bourbon College was entrusted to the Jesuits, Gassendi returned to Digne.

In 1624 at Grenoble, en route to Paris on chapter business, Gassendi published the first of his projected seven Unpopular Essays against the Aristotelians (Exercitationes paradoxicae adversus Aristoteleos …). At Paris Gassendi consolidated an intimate friendship with Marin Mersenne, who, fearful of the inroads of magical pseudonaturalism, counseled Gassendi to discontinue the Exercitationes series and search instead for a sounder philosophy to fill the intellectual vacuum created by the impending dissolution of Aristotelianism. Gassendi chose Epicurus to replace Aristotle. To explore and expound the philosophy of Epicurus, as compatible with both the demands of orthodox Christian faith and the needs of the new science, thenceforth became Gassendi's goal as scholar and scientist.

Gassendi's choice entailed two consequences: (1) epoche and (2) acceptance of both atoms and the void. The first consequence, as a conscientious refusal to commit oneself to any one of several competing theories, allowed Gassendi, in his 1643 Disquisitio metaphysica, to controvert powerfully the purportedly certain deductive system of Descartes's 1641 Meditationes de prima philosophia and to write (indeterminatamente ) another book, his 1647 Institutio astronomica. Galileo had received papal authorization for such a book, but instead had produced his passionately partisan 1632 Dialogo in defense of Copernicus. Gassendi's espousal of atomism exorcised that theory from the curse of popular prejudice and made it respectable in a Christian milieu, but scientific development of it needed the quantitative and experimentally analytic results of Robert Boyle, not the qualitative and imaginatively synthetic descriptions of Gassendi's "compounds." Gassendi's acceptance of the void, however, allowed him to set the mechanics of Galileo's 1638 Discorsi into an isotropically neutral space, and hence to publish for the first time (1649) a scientifically adequate formulation of the principle of inertia.

Bibliography: Opera omnia, ed. h. l. habert de montmor and f. henri, 6 v. in 4 (Lyons 1658–75); repr. in 6 v. (Stuttgart 1964), introd. t. gregory. b. rochot, ed., Pierre Gassendi: Sa vie et son oeuvre (Paris 1955). Comité du Tricentenaire de Gassendi, Actes du Congrés du Tricentenaire de Pierre Gassendi (Paris 1957). t. gregory, Scetticismo ed empirismo: Studio su Gassendi (Bari 1961). j. t. clark, "P. G. and the Physics of Galileo," Isis 54 (1963) 352–370.

[j. t. clark]