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Pardies, Ignace Gaston


(b. Pau, France, 5 September 1636; d. Paris, France, 21 April 1673)


A Jesuit, Pardies deserves a place in the history of physics for having intervened in the debate on the ideas of Newton and of Huygens at certain decisive moments. His work, which is not extensive, is characteristic of a transitional period. The establishment of the Jesuits at Pau in 1622 determined the course of Pardies’s life. His Christian name resulted from the friendship of his father, a royal counselor at the Parlement of Navarre, for the Jesuits. It was at their college that he began his studies.

After finishing his secondary education in 1652, Pardies decided to become a Jesuit. He entered into the novitiate and with it the remarkably well-organized network of Jesuit studies and schools. From 1654 to 1656 at Toulouse he completed the philosophical phase of the curriculum by the study of logic and physics. From 1656 to 1660 he taught humanities at Bordeaux. After studying theology, he was ordained a priest in 1663 and was admitted to the order in 1665.

During the remaining eight years of his life Pardies taught at La Rochelle (1666–1668), Bordeaux (1668-1670), and the College Clermont in Paris (1670–1673). During this period he demonstrated his ability to conduct scientific research while teaching—without neglecting his clerical duties. Indeed, it was while carrying out his ministry at the hospital of Bicetre during the Easter season of 1673 that he contracted a fatal illness.

”A good a cleric as a scientist,” according to the Jesuit chronicler of the Mémoires de Trévoux (1726), Pardies nevertheless presented a problem to his order. From the time of his appointment at La Rochelle his superiors distrusted him because he was known“to pursue strange opinions avidly,”and until his death he was continually obliged to compromise his true views on philosophy and science, to the point that they cannot be established with certainty.

Pardies’s first work, Horologium thaumanticum duplex, dates from 1652; it is not known whether it was ever published. He discussed the subject more completely in a treatise published in 1673. His correspondence from 1661 to 1665 with Kircher offers insight into the source of his initial inspiration, the influence of Maignan on him, and reveals the originality of his “two marvelous clocks.”This originality consists not only in the optical device—a cone receiving light on its base that transformed a stopped-down pencil of solar rays into a luminous plane perpendicular to this pencil; its originality is also reflected in the use of this plane, which rotated with the sun, with either a sundial or a translucent terrestrial sphere. Thus, while still a student of theology, Pardies was engaged in scientific research at a level indicating that he possessed a good education, keen intelligence, and skill in handling instruments.

These qualities also marked his subsequent work. In Discours du mouvement local (1670), Elemens de geometrie (1671), and La statique ou la science des forces mouvements (1673) he presented his material tersely and suggestively. Despite certain inadequacies (notably his account of the laws of impact) it is easy to see in these writings a striving for the most economical axioms obtained through rational reflection on empirical data. During this period Pardies also wrote works of a more philosophical character; the titles indicate criticism of Descartes and reveal how greatly their author felt the need to clarify his position. Discours du mouvement local was published with additional remarks designed to counter the charge of Cartesianism. Yet although Pardies clearly derived a great deal from the Cartesian heritage and felt obliged to defined himself in this regard, Cartesianism was not his principal source. Through the Philosophical Transactions of the Royal Society he was directly informed of the advances of English science (quadrature of the hyperbola and the competition concerning the laws of impact); and in Paris he closely followed the work of the newly established Academie Royale des Sciences and especially that of Huygens, with whom he was in personal contact.

Pardies’s last book offers more of his ideas, which were based on knowledge derived from widely different sources. It contains, for example, his critical study of Descartes’s letter to Beeckman on the speed of light (1634) and his demonstration of the tautochronism of the cycloidal pendulum.

Hindered by the philosophical climate, Pardies made his most important scientific contribution not in his writings, but in his correspondence. It is there that we find the objections that Pardies expressed to Newton concerning his theory of colors and the experimentum cruets—objections that enabled Newton to clarify certain difficult points. Pardies’s unpublished manuscripts contain a theory of waves and vibrations that—judging from the fragments presented by Pierre Ango in 1682—might well have played an important role in the development of physics.

Although Pardies did not have the time to devote the full measure of his abilities to science, he was undoubtedly one of those vigorous intellects that science always needs, along with great discoverers, especially in an age of transition. That he was just such an intellect is evident from his pedagogical writings and his contacts with the pioneers of physics. Leibniz’ impression of him confirms this view. A member of the great line of Jesuit scientists that persisted throughout the seventeenth century, he was, to a greater degree than his predecessors, embroiled in philosophical disputes. Beneath the Aristotelian language that he sometimes sought to preserve, new meanings emerge. His notions, as bold as they were naive, purported to demonstrate the spirituality of the soul by virtue of its capacity to understand the infinite through the “clear and distinct ideas”of certain geometric arguments.


I. Original Works. Pardies’s writings include Horologium thaumanticum duplex (? Paris, 1662); Dissertatio de motu et natura cometarum (Bordeaux, 1665); Theses mathematicae ex mechanica (Bordeaux, 1669); Discours du mouvement local (Paris, 1670), also translated into English (London, 1670); Elemens de geometrie (Paris, 1671), also translated into Dutch (Amsterdam, 1690), Latin (Jena, 1693), and English (London, 1746); Discours de la connaissance des bestes (Paris, 1672); Lettre d’un philosophe a un cartesian de ses amis (Paris, 1672); La creance des miracles (Paris, 1673); Deux machines propres a faire les quadrans avec une tres grande facilite (Paris, 1673); La statique ou la science des forces mouvantes (Paris, 1673); Atlas celeste (Paris, 1674); and Oeuvres de mathematiques (Paris, 1691, 1694, 1701, 1721).

Letters written by Pardies or concerning him can be found in The Correspondence of Isaac Newton, H. W. Turnbull, ed., I (Cambridge, 1959); Oeuvres completes de Huygens, VI-VIII, passim; and The Correspondence of Henry Oldenburg, R. Hall and M. Hall, eds., VIII. Portions of his correspondence remain unpublished.

II. Secondary Literature. See Pierre Ango, S.J., L’optique (Paris, 1682), which draws on Pardies’s MSS; and the unsigned article in Memoires pour servir a l’histoire des sciences et des beaux-arts (Memoires de Trevoux) (Apr. 1726), 667–668. August Ziggelaar, S.J., Le physicien Ignace Gaston Pardies S.J. (1636–1673), vol. XXVI of Bibliotheca Universitatis Havniensis (Odense, 1971), contains the most complete documentation available and eliminates the need to present a more detailed listing of secondary works here.

Pierre Costabel

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