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Gassendi (Gassend), Pierre

Gassendi (Gassend), Pierre

(b. Champte rcier, France, 22 January 1592; d, Paris, France; 24 October 1655)

Philosophy, astronomy, scholarship.

The Gassend family used the form Gassendi, according to the italianism then in style, but Pierre always signed himself Gassend. When a very young man, he was already a principal professor at Digne. His family had him continue his studies, which he pursued at Aix.

In 1614 he was accepted into minor orders and obtained a doctorate at Avignon. Two years later he took holy orders at Aix, where, from 1617 to 1623, he was charged with the teaching of philosophy. He was then initiated into astronomy by Gaultier de la Valette and into humanism by Peiresc, who became his patron.

A partisan of new ideas, Gassendi had printed in Grenoble a first volume of Exercitationes paradoxicae(1624) aimed against the Scholastics; he prudently withheld a second volume. His reputation—and the size of his correspondence—increased, and a cononary at Digne assured his independence (he became provost in 1634).

In Paris in 1624 and again in 1628, he met Mersenne, Mydorge, the du Puy brothers, and Luillier. In 1629-1630 he traveled with the latter in the Low Countries, where he met Isaac Beeckman.

On 7 November 1631 he observed the transit of Mercury, and in his Mercurius in sole visus (1632) he treated the event as a confirmation of Kepler’s ideas. He returned to Digne at the end of 1632 and undertook an extensive study of Epicurus’ thought, in the course of which he expressed his own. At some junctures he clearly departed from the ancient philosopher, but at others he placed statements inspired by materialism next to affirmations of orthodoxy with Which they were difficult to reconcile. He was, however, in no hurry to publish and seems even to have interrupted his researches in 1637 when Peiresc died. He resumed them again under the protection of the new governor of Aix-en-Provence, Louis de Valois, at whose behest he returned to Paris after election to the Assembly of the Clergy, a position he was obliged to renounce in 1641. At the request of Mersenne, he immediately thereafter composed the Cinquiémes objections to the Meditations of Descartes. The Instantiae was published in 1644.

Gassendi’s growing influence led Louis de Valois and Cardinal Alphonse de Richelieu, arch bishop of Lyons, to appoint him professor of mathematics (i.e., astronomy) at the Collège Royal in Paris in 1645. He published a Leçon inaugurale and a Cours, in which he set forth the system of Copernicus, while prudently falling back on that of Tycho. He taught for only a short time, however. His health was uncertain, and in 1648 Louis de Valois called him back to Provence, where he spent several years. His Animadversiones of 1649 contains a portion of his works on Epicurus together with the Greek text and translation of book 10 of Diogenes Laertius.

In Paris once again in 1653, Gassendi produced a third version of his great work entitled Syntagma Philosophicum, but he did not resume teaching. He died at the home of his host, Habert de Montmort, and was buried at St. Nicolas des Champs on 26 October 1655.

Gassendi’s Opera omnia was published in six volumes by his friends in Lyons (1658), according to a plan he had established himself. The first two volumes contain the syntagma; the third, a series of scientific works; the fourth, the astronomical lectures and observations; the fifth, the Liv́es of Astronomers and Epicurean works, as well as the Life of Peiresc; and the sixth, the Latin correspondence he had selected to preserve. The Animadversiones was not reprinted in its original form until 1675.

Although he excited the curiosity and attention of others, Gassendi did not seek to do so. He was not the leader of the “Libertines” and the future “philosophes.” Olivier Bloch, in his authoritative thesis, sees in Gassendi a belated humanist rather than an avantgarde thinker.1 There is no reason to question the sincerity of his testimonies of allegiance to a church of which he was a respected dignitary, as were his best friends, Peiresc and Mersenne. His true intellectual master was Galileo. In the Exercitationes of 1624 Gassendi had demonstrated his philosophic independence, and as early as 12 July 1625 he wrote to Galileo that he shared his Copernican ideas. But he never had to suffer the anxieties of the great Florentine. His choice of Epicurean atomism as a framework for the exposition of his ideas appears to have been more a revolt against Scholasticism than the expression of any profound conviction. Moreover, his erudition embraced all doctrines, including those of the church fathers, whereas he rejected such important elements of Epicureanism as the vertical fall and swerving of atoms.

Gassendi’s eclecticism was that of a skeptic assured that no one doctrine penetrates to the essence of things—indeed, this is a constant aspect of his thought. Yet he proceeded as would a historian for whom the human mind had exhausted all possibilities, in contrast to Descartes, who wrote as if unaware that anyone had ever done philosophy before him. Gassendi’s first published letter (to Pibrac, 8 April 1621) reveals an extreme diversity in what he chose to adopt and a great deal of personal assurance; he rejected only dogmatism, even when Epicurean. Bound by no fixed viewpoint, he could more easily go along with the traditions of his peasant milieu. If his morality preached happiness, his method for attaining it was conformist. A worldly type like Saint-Évremond thought him timid. A fanatic like J.-B. Morin consigned him to the flames. Descartes accused him of nothing less than materialism—thereby contributing more than slightly to the suspicion in which he was held. Gassendi, in turn, treated Descartes as a dogmatist. Moreover, he disappointed the materialists. Gassendi wished, Karl Marx declared, to put a nun’s habit on the body of Lais.2 In reality, Gassendi, believing Aristotle’s metaphysics to be pagan, attempted to establish a metaphysics that would be Christian, but in harmony with the fundamentally anti-Aristotelian contemporary science.

In this undertaking Gassendi may simply have become aware of his own ambiguities.3 A thorough study of the philosophical manuscripts preserved at Carpentras, Tours, and the Laurentian Library, and also of the published works; which repeat and correct each other (Disquisitio, 1644; Animadversiones, 1649; and the posthumous Syntagma, 1658), reveals neither the duplicity nor the denial suspected by Pintard4 but rather an effort to bring the Epicurean elements, accompanied by their materialist tendency, together with the traditional Christian elements. The two had previously been juxtaposed in Gassendi’s writings without being mingled—but not without contradiction. This became evident after the beginning of the dispute with Descartes in 1641 and in the new drafts of the Epicurean works first undertaken in 1642. The factors that Gassendi emphasized to achieve a synthesis between Epicureanism and Christianity were nominalism, finality, and vitalistic or chemical analogies. A discussion of these factors is required before asking whether Gassendi felt that Descartes’s reproaches really hit their target.

Nominalism had been born in a Christian atmosphere, where it remained a minority position, inspired by awareness of the limits of human understanding (modulus intellectionis). Feeble beings that they are, men (homonciones) cannot reach essential truth but only appearances, or phenomena, conditioned by laws that they did not make and cannot understand. God established these laws in order that things might endure and satisfy the needs of living creatures. Man establishes a system of signs, of names, which permits him to identify things perceived and to communicate with other men. But the concepts thus formed are conventions, not universal propositions. The universal does not exist ontologically. God has given man a mind capable only of conceiving the universal as the result of repeated contacts between the senses and well-ordered material realities. In animals imagination and memory record the facts to be retained. In man the rational spirit enables him to combine these representations with a view to action, guided by coherent predictions and based on reflections that take time and that are true inferences and not intuitions of some reality beyond the reach of sensation. But there is an evident providential finality in the Creation thus interpreted, and it is further illustrated by the wonders of the universe, of which man is the consummation and the goal. Hence, final causes are the “Royal Way,” They demonstrate the existence of God. The view was opposed to that of Descartes; and Gassendi, incidentally, refuted the ontological argument on which Descartes relied in much the same way that Kant later did.

Gassendi held that the atoms were the first things created, not in infinite number, as Democritus had said, but in a number sufficient to create the finite universe we know. They are endowed with an unalterable (in French inamissible) movement propelling them without interference in all directions through the void. There is no swerving (no clinamen). The collisions that necessarily take place annul motion and result in the appearance of immobility. Collisions form molecules which are particles identifiable by several attributes. The homogeneous atomic particles for their part are endowed only with shape, resistance, minimum size, and a “weight” that is the effect of their elementary movement. Molecules combine in fewer ways than atoms to form sensible, objects, possessing not powers, or internal qualities capable of activity, but mechanical forces. Various circumstances may liberate these forces in such a manner that impressions are made on other objects, notably the senses of living beings. At this level, other forces become effective—for example, chemical forces.5.

The dynamism that is sometimes noticed in Gassendian physics, and that justifies the expression semina rerum (borrowed from Lucretius) to designate the atoms, was merely this accumulation of an energy potential, conceivable even in biology. For living bodies are subjected to the same laws as others. Life is composed of movements of the “flower of matter,” the animal soul, which in a way resembles Descartes’s animal spirits and subtle matter. Science is thus relative to our needs; a view in which there was both sensationalism and pragmatism. Thus, Gassendi was not only a belated humanist but also a precursor of Locke, Condillac, and the positivists and empiricists of the eighteenth and nineteenth centuries.

These ideas contained the entire arsenal upon which future materialists could draw. Yet Gassendi had no thought of being a materialist in the later sense of d’Holbach or Marx. The clash with Descartes had revealed to him the way in which his works, still unpublished, could scandalize certain readers; his role as a priest led him to take this danger into account. But until then he had been able to conjoin faith with Epicureanism with as little fear as Galileo had earlier felt in juxtaposing Copernicus and the Bible.

Galileo had pointed out in his letter to the grand duchess of Florence (see below) that the Bible had originally been addressed to the early Jews in terms that they could understand, while Copernicus, for his part, had offered his work to the pope, and it was not at first thought heretical. By the same token, in Gassendi’s view, God had the power to make the world from atoms, as the Epicureans held, and was equally able to illuminate it by making the earth revolve around the sun on the Copernican hypothesis.

Galileo explained his theological position in relation to science in 1615 in his letter to the grand duchess of Florence. Christine of Lorraine. The argument was immediately and widely disseminated, and Gassendi undoubtedly saw it at Aix. It was published in Latin in Strasbourg as early as 1635.6 although in response to the condemnation of 1633. Descartes’s opposition also obliged Gassendi to take “precautions.” The word is Mersenne’s, who, by publishing the Cinquiémes objections had provoked the dispute with Descartes. He spoke of precautions in praising Gassendi’s works in a letter to Rivet (8 February 1642).7 That was precisely the date on which Gassendi undertook a new draft of his Epicurean works. Gassendi may probably have made these modifications in order to persevere in the same project, not to remove ambiguities or to modify it in some unexpected way. Mersenne gave his approbation to the earlier version, while expressing satisfaction with improvements in the new edition. Freethinkers were the only ones who judged differently and for their own reasons: they hoped that this physics would teach man to dispense with metaphysics.8.

Was such a result what Gassendi wished? Not at all. In the seventeenth century it was possible to conceive of God’s having created the universe in a single stroke, but after a model that permits the most convenient analysis. The “fable du monde,” which Descartes imagined to be separate from dogma without contradicting it, played a finalist role despite its author’s intentions. The atomic model could be employed in the same fashion. An admirer of Gassendi, the physician Deschamps, asked whether, without impiety, one could say that.9.

Gassendi’s influence on epistemology may now be stated more precisely. Koyré summarized it by saying that Gassendi contributed to the new science “the ontology that it needed,”10 In order to eliminate “powers” and “acts,” “accidents” and “qualities,” whether occult or not, it was necessary to suppose fixed and measurable data in a medium that in no way influences what is observed. Such are the atoms, endowed with shape, solidity, impenetrability, and a natural tendency to motion, which is weight. Such is the void in which bodies move without interference and without any change occurring in their nature through mere endurance. Time does not “eat away” at things; rather their mechanical and spatial relations change in the course of time. Contrary to the Scholastic view, space and time are neither substance nor accident. They exist when their content disappears and when nothing is happening. They establish the general frame of any knowledge of reality—with atoms redividing in a homogeneous void and moving in the unalterablecourse of time. Gassendi was one of the first to state this universal, categorial law of space and time.

Despite his influence on the ontology of classical physics, Gassendi’s scientific successes were not of the first rank. He owed what he achieved to his fidelity to the Democritean schema. Thus his study of Parhélies (1630) suggests a corpuscular explanation of light. His patient and thorough method made him a pioneer of observational astronomy, in which field Galileo had already set the example in 1610.11 But the observations, which almost fill the fourth volume of his Oeuvres, could serve only as a model for his contemporaries without leading him to any major discovery. For example, he corrected the geographical coordinates acknowledged for use in navigation in the Mediterranean, and he rejected the discovery of Jupiter’s new satellites announced by de Rheita in 1643.

The observation of the transit of Mercury, in which he alone was successful and which confirmed Kepler and, indirectly, Copernicus, caused widespread discussion. Koyré, however, reproaches him for having disregarded the mathematical form that enabled Kepler to determine the elliptical orbits of the Planets.12 Numerous sketches of various aspects of Saturn did not suggest to him the ring hypothesis, which Huygens proposed in 1659 without access to information that was much superior. Gassendi remained a prisoner of what the senses, even when fortified, are able to show. The Cours of 1644 at the Collége Royal (published in 1647) prudently presented Tycho Brahe together with Copernicus, while leaning sufficiently toward the latter to shock J.-B. Morin. In the De proportione qua gravia decidentia accelerantur of 1645, as in the De motu impresso, Gassendi defended—against the criticism of Le Cazre—the law of freely falling bodies, in which velocity is proportional to the square of the time elapsed and not to the distance traversed. But he never understood the importance of its having been deduced either from simple observations of motion on an inclined plane or in any other way.

In 1654 Gassendi joined to his other lives of astronomers the Life of Copernicus, in which the trial of Galileo, although not omitted, is barely mentioned. He thus insisted on the hypothetical and mathematical character of Copernicus’ work, whereas in 1647 the Institutio astronomica had explained the condemnation of Galileo by considerations relating to Galileo himself, but presenting no objections to Copernicus’ theories.13 It is further worth noting that Gassendi followed Galileo in the error of regarding the phenomen on of the tides as a proof of the motion of the earth. As was well known, the periodicity of the tides does not correspond to that of the diurnal movement, and Descartes did not make this mistake.14.

On one point—and it is an important one— Gassendi was more successful than Galileo: he correctly stated the principle of inertia. The experiment of the De motu impresso a motore translato, performed in 1640 in Marseilles, overthrew the argument of Copernicus’ opponents against the movement of the earth. Gassendi arranged to have a weight dropped from the top of a vertical mast on a moving ship in order to demonstrate that it fell at the foot of the mast and not behind it, thus sharing in its fall the forward motion of the ship. Galileo considered the experiment unnecessary; he foresaw the result by reasoning.15 Others, notably Bruno, had already spoken of it. But Gassendi understood that the composition of motions is a universal phenomenon: Every movement impressed on a body in motion in any direction whatsoever persists in Democritean space, which has neither up nor down. Motion is, in itself, a physical state, a measurable quantity, not— as the Scholastics maintained—the change from one state to another. It changes only through the interposition of another movement or of an obstacle.

Furthermore, Gassendi also corrected the formulation given by Kepler, for whom inertia was a tendency to rest: in classical physics, inertia is indifference to both motion and rest. On this point, Gassendi was guided by Galileo’s experiments on the pendulum, in which motion is maintained without any supplementary impetus. In addition, Kepler’s idea of magnetic effluents or forces gave him an, intimation of the existence of universal attraction or, rather, universal interaction—although he was no more successful than Descartes in conceiving its transmission otherwise than by contact.16.

Gassendian atoms and Cartesian subtle matter belong, as has been seen, to a single period of thought. Moreover, the idea of inertia was common to Beeckman, Gassendi, and Descartes, who all knew each other, and we know that Newton read Gassendi, as did Boyle and Barrow.

In 1650, on a mountain near Toulon, another experiment repeated the famous one of the Puy-de-Dôme.17 Gassendi fully appreciated the value of Pascal’s work. But the latter, in the Èquilibre des liquerṣ,,18 speaks indiscriminately of “weight and pressure of the air,” whereas, guided by the corpuscular picture and not by the hydrostatic scheme referred to in Pascal’s title, Gassendi could differentiate weight (which is constant for a given mass of air) from pressure (which varies according to the state of agitation, dilation, or contraction of this same mass). It is variations in pressure that affect the barometer and that measure not only the approximate height of the “column of air” but also the changes of state of the atmosphere, which are capable of influencing subsequent weather conditions. Of course, the barometric vacuum proves that the natural vacuum is not impossible; but what happens in the tube depends only an what happens outside. Koyré rightly points out that in this regard Gassendi anticipated Boyle, who read him closely and regretted not having done so earlier.19.

Gassendi applied his empirical and experimental sagacity to other fields, often in collaboration with Mersenne. Together they estimated the speed of sound as 1,038 feet per second, a passable approximation for the time.20 Physiology and dissection also interested Gassendi, as did all of natural history. However, he never completely renounced a false observation made at Aix in his youth when Payen made him “see” a communication between the two parts of the heart; but at least he esteemed Harvey and Pecquet. Numismatics and music also occupied him on occasion.

It is evident that Gassendi’s influence on science was more philosophical than technical and more critical than systematic. He rationalized physics, by introducing quantity into it through the measurements he undertook but above all by introducing atoms, those mutually combinable units that are capable of joining together in molecules and of producing measurable bodies. It is regrettable that with excessive modesty he reframed from propounding general views of the sort that can direct and enrich experiment a priori and that he did not envisage the possibility of applying mathematics to concrete, physical cases.21.


1. In Gassendi one sees primarily a precursor of Locke and Condillae, mentioned later in this article, as well as Hume, See Tricentenaire de Gassendi, pp.69, 227.

2. “Avant-propos” to “Mémoire sur Démocrite et Épicure.” in Oeuvres, J. Molitor. trans., I (Paris, 1946), xxii.

3. This and the following three paragraphs have been freely inspired by the excellent thesis of M. Bloch (see below), who generously lent it to the author.

4. Cf. Libertinoge érudit (Paris. 1943). p. 301, passim.

5. On this point, Bloch rehabilitates Etienne de Clave, a chemist condemned in 1624 by the Parlement of Paris.

6. Letter, in Le opere di Galileo Galilei. Favaro, ed. (Florence. 1890-1909), V, 309 ff. Gassendi does not approach the position of “double truth” to the extent that Bloch (see especially his ch. 11) thinks he does in his desire to reconcile Epicureanism and literal dogma. He thought he could juxtapose not two truths but facts equally real although differently expressed. Misunderstanding.” taught him what “precautions” (see following note) to take, precautions that Bloch sets forth with extreme precision; but these do not go as far as fideism.

7.Correspondence du P. Mersenne, XI, 38: “M. Gassendi réfute puissament, dans sa Philosophie Épicurienne, tout ce qui est contre le christianisme, et, comme vous avez fort bien remarqué, il y prend des précautions.” Rivet did not necessarily see what Mersenne was talking about. Mersenne, however, knew the drafts that preceded the one begun on this date as well as the drafts of the Instantiae, which was later joined to the Cinquièmes objections and Descartes’s Responsa to form the Disquisitio metaphysica (1644).

8. The author’s conclusions in this and the preceding paragraph are inspired by new material introduced by Gassendi in later editions that has been studied in depth by Bloth; the author’s opinions differ, in accordance with his knowledge of the respective positions of Descartes, Galileo, Gassendi, and mersenne in regard to each other.

9. Letter of 14 Aug. 1642, in Correspondence du P. Mersenne XI, 229-231.

10.Tricentenaire, pp. 176, 186.

11. Galileo sent Gassendi a telescope through Diodati; see letter of 25 July 1634 from Galileo to Diodati.

12.Tricentenarie, p. 188. n. 9. However, the Syntagma, I, 639a-b, mentions the elliptical trajectories of kepler.

13.Opera omnia (Lyons, 1658), V, 60b, end of book III, ch. 10.

14.Principes, IV, 49-52.

15.Dialogo, in Le operer di Galileo Galilel, VII 171; and Koyré Etudes galiléennes, pp. 215, 229, 249, 252; and in Tricentenaire, pp. 189 ff.

16. Despite everything that set them apart, Descartes and Gassendi were often bracketed by authors of the end of the seventeenth century. See also n. 5 and the corresponding text.

17. Gassendi had spoken of the Puy-de-Dôme experiment in a supp, to the Animadversiones (1649) and of his own in a letter (6 Aug. 1652) to Bernier, who had assisted him in that experiment. (Dating the letter “anno superiore,” he called Bernier’s memory into question: his own “diaire” testified that the experiment took place on 5 Feb. 1650.) All this is taken up again in the Syntagma (Opera omnia, I, 203-216). See Rochot’s articles in Aventure de l’esprit (Mélanges Koyré) and in Koyré, Tricentenaire, pp. 184 ff.

18. Pléiade ed., pp. 383 ff.

19.Tricentenaire, pp. 184 ff,; see also Bloch, ch., 8, especially n. 190, opposing Koyré.

20.Tricentenaire, p. 180.

21. Did Did Gassendi read the Saggiatore? See Le opere di Galileo Galilei, VI, 232, as well as the letter to Liceti (Jan, 1641), ibid., XVIII, 295: “The book of nature is written in mathematical language,”


I. Original Works. The contents of the six vols. of the Opera omina (Lyons, 1658), with a preface by Sorbiére, are summarily described in the text. The work has been reprinted twice: N. Averrani, ed. (Florence, 1727); and in facs. (Stuttgart, 1964), with a pref. by T. Gregory.

Following is a list of Gassendi’s principal individual works.

Scientific Works. Into this class fall Mercurius in sole visus et Venus invisa (Paris, 1632; 1658 ed., vol. IV); De apparente magnitudine solis humilis et sublimis epistolae quatuor (Paris, 1642; 1658 ed., vol, III); De motu impresso a motore translato epistolae duae (Paris, 1642; 1658 ed., vol. III), two letters to Dupuy, to which a third, to Gautier contra Morin and datged 1643, was added in the 1658 ed. (Gassendi’s friends had published the Gautier letter earlier [Lyons, 1649] without his knowledge); Oratio inauguralis habita in Regio Collegio, anno 1645, die Novembris XXIII, a P. Gassendo (Paris, 1645; 1658 ed., vol IV); De proportione qua gravia decidentia accelerantur (Paris, 1646; 1658 ed., vol. III); Institutio astronomica juxta hypotheseis tam veterum quam Copernici et Tychonis. Dictata a Petro Gassendo. Ejusdem oratio inauguaralis iterato edita (Paris, 1647; 1658 ed., vol. IV); and Tychonis Brahei . . . N. Coernici, G. peurbachi et J. Regiomontani . . . vitae (Paris, 1654; 1658 ed., vol V).

Philosophical Works. This second class includes Exercitationum paradoxicarum adversus Aristoteleos libri septem, in quibus praecipua totius Peripateticae doctrinae atque dialecticae excutiuntur; opinions vero aut nove, aut ex vetustioribus obsolete stabiliuntur, liber primus: In doctrinam Aristoteleorum universe, issued independently (Grenoble, 1624); bk. 2, In dialecticam Aristoteleorum, did not appear until the 1658 ed. (vol. III) with the shortened title Exerctitationes paradoxicae adversus Aristoteleos, in quibus . . . It was separately published shortly afterward as Exercitationum paradoxicarum liber alter in quo dialecticae Aristoteleae fundamenta excutiuntur (The Hague, 1659); a text and French trans. appeared as Dissertations en forme de paradoxes contre les aristotéliciens, B. Rochot, ed. and trans. (Paris, 1959), in which bk. 2. is corrected according to the MS at the Laurentian Library (this MS was formerly at Tours but was stolen from there by Libri).

Epistolica exercitatio, in qua praecipua principia philosophiae R. Fluddi, medici, reteguntur, et ad recentes illius libros adversus R. P. F. Marinum Mersennum scriptos respondetur (Paris, 1630; 1658 ed., vol. III).

The Disquisitio metaphysica seu dubitationes et instanitae adversus R. Cartesii metaphysicam, et responsa (Amsterdam, 1644; 1658 eds., vol. III) consists of the Objectiones quintae of 1641 with the publisher Sorbuère’s addition of the Instantiae of 1642, after Descartes’s Responsa. A text and French trans. of the Disquisitio was published as Recherche de la métaphysique, B. Rochot, ed. and trans. (Paris, 1962).

De vita et moribus Epicuri libri octo (Lyons, 1647; 1658 ed., vol. V).

Animadversiones in decimum librum Diogenis Laërtii, qui est de vita, moribus placitique Epicuri, 3 vols, (Lyons, 1649; 2nd ed., 2 vols., 1675), was reproduced only in part in the 1658 ed. The Greek-Latin text of Diogenes, with philological notes, does appear in vol. V. The reworked doctrinal commentary was incorporated into the Syntagma philosophicum (see below). The Philosophiae Epicuri syntagma, cum refutationibus dogmatum quae contra fidem christanam ab eo asseta sunt, oppositis per Perum Gassendum (1658 ed., vol. III), a sort of Epicurean breviary added as an appendix to to vol. II of the Animadversiones, appeared separately (The Hague, 1659) with the preface that Sorbièe had placed at the head of the 1658 ed.

His masterpiece, Syntagma philosophicum (logica, physica, ethica), was published posthumously (1658 ed., vols. I–II).

Correspondence. The Letters familières àFr. Luillier (hiver 1632-33), B. Rochot, ed. (Paris, 1944), is based on a MS that belonged to the heirs of the provost of Digne, now in the Bibliothèque Nationale (fonds latin 2643). The MS contains Gassendi’s drafts of the Latin letters in vol. VI of the 1658 ed. Most of the letters addressed to him in the same vol. are in the Bibliothèque Nationale. The French correspondence with Peiresc is in Lettres de Peiresc, Tamizey de Larroque, ed., IV (Paris, 1893). Gassendi is frequently mentioned in correspondence of the period; see especially Correspondence du. P. Mersenne, C. de Waard, Marie Tannery, and B. Rochot, eds. (Paris, 1932-). The bulk of his extensive correspondence in French and Latin is far from entirely known.

Miscellanleous Works. The biography De Nicolai Claudii Fabricii de Peiresc, senatoris aquisextiensis, vita (Paris, 1641; 1658 ed., vol. V) appeared in English as The Mirrour of True Nobility and Gentility, Being the Life of . . . N.C. Fabricius, Lord of Periesk, W. Rand, trans, (London, 1657). It is especially useful as a source for the historian of early seventeenth-century science.

A curious, and anonymous, pamphlet of 1654 designed to calm widespread fears occasioned by an eclipse of the sun is reasonably attributed to Gassendi. It was reprinted by B. Rochot, ed., in Bulletin de la Société d’tude du XVIIesiècle, no 27 (Apr. 1955), 161-177.

II.Secondary Liteature. The following items have been selected from the bibliography (343 items, including MSS, printed texts, biographical and doctrinal studies, and various articles) in the thesis of Olivier René Bloch, La philosophie de Gassendi: Nominalisme, matérialisme et méta physique (Paris, 1971); F. Bernier, Abrégé de la philosophie de Gassendi, 2nd ed., 7 vols, (Lyons, 1684); Henri Berr, Du scepticisme de Gassendi, B. Rochot, trans. (Paris, 1960), a trans, of the 1898 thesis An jure inter scepticos Gassendus numeratus fuerit; [J. Bougerel], Vie de Pierre Gassendi (Paris, 1737), which should be examined carefully because the author had access to documents that are now lost; G. S. Brett, Philosophy of Gassendi (London, 1908); G. Cogniot, “Pierre Gassendi, restaurateur de l’épicurisme,” in La pensée, no. 63 (Sept.-Oct. 1955); P. Damiron, Histoire de la phiosophie au XVIIesiècle (Paris-Neuchâtel, 1954), ch. VI, pp. 103-116; Tullio Gregory, Scietticismo ed empirismo, Studio su Gassendi (Bari, 1961); Pirre Humbert, L’oeuvre astronomique de Gassendi (Paris, 1936), completed by philosophes et savants (Paris, 1953), pp. 79-107; A Koyré, Études galiléennes (Paris, 1939), pp. 237 ff., repr. (Paris, 1966), pp. 304 ff,; F. A. Lange, Geschichte der Materialismus und Kritik senier Bedeutung in der Gegenwart, 2nd ed., 2 vols. (Iserlohn, 1837-1875), which appeared un French as Histoire du matérialisme, B. Pommerol, trans., 2 vols, (Paris, 1921), and in English as The History of Materialsm . . . , E. C. Thomas, trans., 3rd ed. (London, 1957), contains a section on Gassendi; Kurd Lasswitz, Geschichte der Atomistik vom Mittelalter bis Newton, 2 vols. (Hamburg-Leipzig, 1890; 2nd ed., 1928), II, 126-188; L. Mabilleau, Histoire de la philosophie atomistiue (Paris, 1895), pp. 400-422: P. Pendzig, Pierre Gassendis Metaphysik . . . (Bonn, 1908); René Pintard, Libertinage éudit, 2 vols. (Paris, 1943), which contains, in vol. I, numerous analyses in which Gassendi is portrayed as the leader of libertine tétrade and, in vol. II, an important bibliography (see also the MSS examined in his La Mothe le Vayer, Gassendi, Guy Patin (Paris, 1943]); B. Rochot, Les travaux de Gassendi sur Épicure et l’atomisme (Paris, 1944); G. sortais, La philosophie moderne depuis Bacon jusquà Leibniz, II (Paris, 1922); J. S. Spink, Free Thought From Gassendi to Voltaire (London, 1960); and P. F. Thomas, La philosophie de Gassendi (Paris, 1889), More a summary than an interpretation, it does not take into account the evolution of Gassendi’s thought as represented by the Syntagma. Two collections of studies are Pierre Gassendi, sa vie et son oeuvre, Centre International de Synthèse (Paris, 1955); and Tricentenaire de Gassendi, Actes du Congrès de Digne, 1955 (Paris-Digne, 1957).

The MSS enumerated by Bloch are in the Bibliothéque Nationale and in the libraries of Tours (706-710), Carpentras, and Florence (Laurentian). Biographical documents are at Aix-en-Provence, Digne, Grenoble, Marseilles, Munich, Oxford, Stuttgart, and Vienna; in the Archives du Ministère de la Guerre, Paris; and in the Bibliothèque Nationale (fonds français 12270 and fonds Dupuy.

Some texts have been translated into Polish by H. L. Kolakowski (Cracow, 1964) and into Russian by Sitkovsky (Moscow, 1966), with Studies.

It should be noted that the important study by G. Gusdorf, Révolution Galilèenne, vol III. of Les Sciences Humaines et la Pensée Occidentale, 2 vols. (Paris, 1969), was used in the preparation of this article.

Bernard Rochot.

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Gassendi, Pierre


(b. Champtercier, France, 22 January 1592; d. Paris, France, 24 October 1655),

natural philosophy, atomism, astronomy, optics, mechanics. For the original article on Gassendi see DSB, vol. 5.

Since 1972, when Bernard Rochot wrote his entry for the DSB, Gassendi has been the object of increasing scholarly attention, and new light has been shed on virtually all aspects of his multifaceted philosophical and scientific activity. Besides adding some factual information to Rochot’s biographical account, the present postscript aims at providing a reassessment of four crucial issues, namely:

  1. the relation between Gassendi’s epistemological convictions and his scientific practice;
  2. the nonreductionist character of Gassendi’s matter theory, in which a crucial role is played by seminal virtues and organizing principles;
  3. Gassendi’s engagement in defense of Galileo Galilei’s theory of motion, of which he fully understood the cosmological implications;
  4. and, finally, Gassendi’s problematic attempts to derive the Galilean law of free fall from a physical explanation of gravity and to reconcile the principle of inertia with the laws governing the motion of atoms.

Early Intellectual Life . Second child of Antoine Gassend and Françoise Fabry, Pierre begun his schooling at Digne, and in 1602 was sent to Aix-en-Provence, where he studied philosophy under Father Philibert Fesaye and theology under Professor Raphaelis. In 1613, he was appointed principal of the College of Digne and professor of rhetoric. One year later he obtained the doctorate in theology at Avignon and was elected canon of the Cathedral of Digne. Ordained a priest in 1616, he became a professor of philosophy at Aix in 1617. In 1618 he started his astronomical observations under the guidance of Joseph Gaultier. The first entry in Gassendi’s astronomical diary records the observation of the comets made in Gaultier’s company in November 1618.

When, in 1621, the Jesuits took over teaching at Aix, Gassendi decided to return to Digne. His trips to Paris (1624, 1628, 1629, 1631) were marked by some important encounters: Marin Mersenne introduced him into his circle; the brothers Pierre and Jacques Dupuy, wardens of the king’s library, admitted him into their academy; with Elia Diodati, Gabriel Naudé and François de La Mothe Le Vayer he was to form the so-called Tétrade; with Ismael Bouillau he discussed astronomical matters; and with François Luiller he traveled through the Low Countries between 1628 and 1629.

However, the most important figure in Gassendi’s early intellectual life was certainly his first mentor, Nicolas Fabri de Peiresc, counselor to the Parliament of Provence and owner of an impressive library and of a collection of instruments. Peiresc offered Gassendi material and intellectual support, and the two shared an interest in humanism, philology, numismatics, cartography, astronomy, optics, and physiology.

Peiresc was always the first to be informed about the evolution of Gassendi’s Epicurean project. In 1626, Gassendi announced to Pieresc his intention to write an apology of Epicurus; and in 1631 he communicated his decision to extend his project beyond the field of ethics to include all of Epicurus’s philosophy (De vita et doctrina Epicuri). In the course of 1634, Gassendi sent to Peiresc eight manuscript quires (cahiers) containing the fruit of his work. These cahiers, which contained an apology De vita et moribus Epicuri(an updated version of which was published in 1647) and a preface De philosophia Epicuri universe, are now lost, but a manuscript containing a copy of the preface resurfaced at the British Library.

Several interests and engagements interfered with the elaboration of the Epicurean project. In 1629 Gassendi wrote an astronomical treatise, the Parhelia; in 1630 he published the Epistolica exercitatio, an attack against Robert Fludd written at Mersenne’s request; in 1631, he observed the transit of Mercury; in 1634, he composed the De veritate against Herbert de Cherbury and the first letter De apparente magnitudine solis humilis et sublimis(published in 1636).

Contrary to what has sometimes been maintained, the Exercitatio of 1630 was not intended as an attack against alchemy as such, but rather against the synthesis of alchemy, kabbalah, and religion operated by Fludd. In the Exercitatio a distinction is drawn between “false alchemy” and “real alchemy.” While rejecting Fludd’s interpretation of Genesis in alchemical terms, and his identification of God with the Platonic world soul, Gassendi recognized the importance of alchemy for natural philosophy, and even expressed the conviction that the transmutation of metals would become possible, if the seeds of gold were discovered. In the Exercitatio one also finds the hypothesis, which reappears in the Syntagma, that the generation and transformation of metals resemble biological processes, as they are brought about by seminal powers.

Both the Exercitatio against Fludd and De veritate against Herbert de Cherbury echo the epistemological stance already taken in Gassendi’s Exercitationes of 1624. In all these works Gassendi chastises the ambition of arriving at universal truths by means of a purely intellectual act (be this the intellectus principiorum of the scholastics or the instinctus naturalis of Herbert de Cherbury) and opposes to the dogmatic ideal of a scientia per causas his own model of a philosophia aperta et sensibilis, based on a direct reading of the book of nature. When, in March 1634, Gassendi left Digne for an extended sojourn at Peiresc’s villa at Aix-en-Provence, the two men engaged in an intense scientific activity that perfectly conformed to Gassendi’s ideal of a descriptive-cumulative science. Between 1634 and 1636, they undertook studies of meteorological phenomena as well as geological investigations concerning the nature of stones, minerals and fossils, the formation of caverns, and the circulation of waters; they planned to produce a lunar atlas, for which Claude Mellan began to make the engravings; most importantly, Gassendi followed Peiresc in his numerous microscopic observations and in his study of the physiology of vision.

Peiresc had acquired a Drebbel microscope as early as 1623, and he used the instrument to test recent anatomical and physiological discoveries, including William Harvey’s discovery of the circulation of blood and Gaspare Aselli’s discovery of the lactic vessels. Interestingly the two findings appeared to be incompatible with one another, for Aselli believed, in accordance to Galen’s view, that these vessels transported intestinal lymphatic material to the liver, the organ in which blood was produced. Gassendi himself found it difficult to dismiss Galen’s authority. While in 1629 he thought that Harvey’s theory of the continuous circulation of blood was probable and well-founded, in the Syntagma he would eventually endorse some of Jean Riolan’s and Guy Patin’s objections. The anatomical observations conducted with Peiresc were to be invoked in the Disquisitio metaphysica and in the Syntagma as a proof of the existence of final causes in the biological realm. Peiresc and Gassendi also anatomized the eyes of many different animals, seeking a physiological, rather than psychological, explanation of the problem of retinal inversion. After being inverted by the convex crystalline, the image was reinverted by the concave retina and reflected back into the vitreous humor.

The Microscope and the Atoms . If Peiresc’s enthusiasm for the microscope had been essentially directed toward its descriptive capacity, Gassendi appreciated it mostly for its analytic potential, viewing it as an ally in the rehabilitation of atomism. Waiting for the day that microscopes would become so powerful as to make atoms visible, Gassendi used the available instruments to collect empirical evidence in favor of his theory of matter. This evidence was, however, somewhat ambivalent. If applied to little organisms, the microscope revealed an immense variety of different forms underneath a seemingly homogeneous surface: the fact that an insect no bigger than a dot, when put under a magnifying lens, displayed a great variety of organs, appeared as an illustration that innumerable atomic shapes could combine to form compound bodies. The microscopic observation of salts and minerals suggested instead that nature repeated its basic patterns from the macroscopic world down to the atom. In 1636, after a visit to saline springs, Gassendi wrote to Peiresc that the microscopic observation of salts seemed to validate the principles of Epicurean philosophy: the fact that these cubic, hexahedral, or octahedral solids were made out of components of the same shape allowed for the conclusion that this shape was preserved up to the level of atoms. His observation of salts, moreover, further strengthened Gassendi’s belief in the existence of seminal virtues in charge of organizing the corpuscles according to pre-established patterns.

Since his visit to the chemist Jan Baptista van Helmont, in 1629, Gassendi had begun to embed ideas of Paracelsian extraction within his Epicurean program, a task rendered easier by Lucretius’s use of the expression “seeds of things” (semina rerum) to designate atoms. Of particular influence on Gassendi’s treatment of so-called natural res mixtae (animals, plants, and fossils) was the Paracelsian synthesis provided in Petrus Severinus’s Idea medicinae (1571). In the Syntagma, Gassendi explains that growth and internal organization of all beings, from metals and crystals upward, are due to seminal forces which are not immaterial principles, but rather physical agents composed of very active corpuscles endowed by God with a program. But how exactly the “divine and incomparable Architect” has set up the “occult internal economy” that leads to the formation of the seeds responsible for the generation of living forms remains unknown, as Gassendi professes in his Syntagma.

However, he explicitly adopts Severinus’s term mechanical spirits to account for this process. There is, from the historians’ point of view, some irony in this seemingly oxymoronic expression. It has often and convincingly been argued that Gassendi’s atomism was not of a mechanical sort, if by “mechanical” we understand the Cartesian program of reducing all upper-level phenomena to the structure of, or collisions by, material corpuscles. But before Robert Boyle popularized the term mechanical philosophy, this predicate had a wide variety of meanings. In fact, when invoking Severinus’s “mechanical spirits,” Gassendi meant intelligent agents, which had nothing in common with René Descartes’s inert chunks of matter.

Astronomical Observations and Optical Puzzles . A further influence on Gassendi’s matter theory was astronomy and in particular the observations he carried out in the 1630s. In his Admonitio of 1629, Johannes Kepler had predicted a solar transit of Mercury for 7 November 1631, explaining how the shadow of the planet on the solar disk could be used to calculate its apparent size. Gassendi, who was in Paris at the time, was the only person to observe the phenomenon predicted by Kepler. Using a telescope, he

projected the image of the sun on a paper screen, and on 7 November he saw a tiny shadow appear on the solar disk. As he explained in the Mercurius in Sole visus, the smallness of the apparent size of Mercury seemed to indicate that the solar system was much bigger than so far believed. The observation of the transit of Mercury triggered Gassendi’s interest in optical questions. Between 1636 and 1641 he performed various experiments to measure the shadows cast by a larger or smaller apparent sun. In his letters De apparente magnitudine solis humilis et sublimis, Gassendi invoked the corpuscular composition of light rays and atmosphere to account for some curious optical phenomena. He explained that when the sun is at the horizon more light rays are absorbed by the atmosphere than when it is at the zenith, so that less luminosity reaches the eye. This provokes a dilation of the pupil, which makes the sun appear larger. The optical experiments further reinforced Gassendi’s conviction that natural philosophy cannot rely exclusively on mathematical reasoning, which is often misleading: that the midday sun produces the smallest shadows contradicts the principles of geometrical optics, which would require that the shadow cast by the greater apparent sun (i.e., the horizon sun) be smaller than the one cast by the smaller apparent sun (i.e., the sun at the zenith).

Atoms, Mechanics, and Cosmology . When Peiresc died, on 24 June 1637, Gassendi was so devastated that he interrupted his scholarly activity as well as his epistolary contacts for nearly two years. In 1638, however, he encountered the new governor of Provence, Louis de Valois, who was to become his new protector. The two men entertained a very dense correspondence. Besides keeping de Valois informed about the advancement of his research, Gassendi devised for him a philosophy course, articulated in fifty-nine letters written between October 1641 and November 1642. The course followed the contents and the structure of the De vita et doctrina Epicuri. Gassendi started with an apology for Epicurus, continued with a historical analysis of various philosophical traditions, then offered a history of dialectics, and finally engaged in a reconstruction of Epicurus’s thought, notably of his canonics and physics. The letters reveal how different Gassendi’s relation with de Valois was from that with Peiresc. He treated the new mentor with the respect due to a prince and the benevolence due to an eager, but not particularly talented student.

In October 1640, de Valois witnessed a spectacular event of which he was also the sponsor: Gassendi left the port of Marseille on a galley to perform an experiment imagined by Galileo in the Dialogo. Gassendi verified that a ball dropped from the top of the mast landed at its foot no matter whether the ship was at rest or sailing at high speed. The experiment had important cosmological implications, for it falsified one of the crucial arguments against the daily motion of Earth. In the year of Galileo’s death, 1642, Gassendi published the Epistolae duae de motu impresso a motore translato, in which he provided a physicomathematical analysis of this experiment, as well as an examination of its cosmological implications. One of the major conceptual novelties introduced there was the identification of gravity with the attractive force of Earth. According to Alexandre Koyré’s interpretation, which many scholars have endorsed, the recognition of the external nature of gravity allowed Gassendi to publish the first correct statement of the principle of rectilinear inertia. This judgment is, however, overly generous. True, in the Epistolae and in the Syntagma, Gassendi does state that in an imaginary void space a stone set in motion would persist in a state of uniform rectilinear motion. But when talking about the behavior of bodies in the real world, he does not hesitate to describe uniform circular motion (e.g., of planets, or of a ball rolling on Earth’s surface) as maximally natural. Also, contrary to Galileo, he does not have the slightest notion of a centrifugal force. Moreover, as Koyré himself recognized, the principle of inertia is incompatible with Gassendi’s laws of microscopic dynamics. Far from being indifferent to motion and rest, Gassendi’s atoms are endowed with an innate tendency to move at maximum speed, so that the variety of motions of macroscopic bodies must be explained as the result of the clashes among the underlying atoms. Rather than in the formulation of some principle of inertia, the importance of Gassendi’s Epistolae resides in the emphasis that Gassendi places on the relation between Galileo’s new science of motion and Copernican cosmology.

Gassendi’s attempt to derive Galileo’s law of natural acceleration from a causal analysis of free fall is also interesting, although ultimately unsuccessful. Contrary to Descartes, who considered Galileo’s theory of motion a mathematical abstraction, incompatible with any mechanistic explanation of gravity, Gassendi stubbornly tried to devise a causal account of free fall that could be reconciled with the odd-number law. In the Epistolae de motu he described falling bodies as being subjected to the joint action of two forces. The first, which he calls the vis attrahens, is the force of the earth, which emits chains of magnetic particles capable of reaching distant bodies and carrying them back. The second, which he calls vis impellens, is the force of the air, which rushes upward to fill the space evacuated by the falling body and thereby produces an additional pressure from behind.

In the course of his polemics with the Jesuit Pierre Le Cazre, which led to the publication of the Epistolae de proportione qua gravia decidentia accelerantur(1646), Gassendi came to the conclusion that the vis attrahens was by itself capable of bringing about an acceleration according to Galileo’s odd-number law. But the relation Gassendi establishes between causal explanation and mathematical analysis of fall appears forced and artificial. For in no way can he account for the fact that a force acting through contact, by means of discrete pushes, will bring about a continuous acceleration. In the Syntagma Gassendi reconfirms his support for Galileo’s theory of motion, without, however, subscribing to its mathematical foundation. He denies that physical magnitudes can be made out of mathematical points, and postulates the composition of space and time out of extended minima.

In the Epistolae and the Syntagma, Gassendi stressed the conjectural character of his explanation of gravity. He claimed to be certain about the general mode of action of vis attrahens, which can operate only through contact, but admitted his ignorance concerning the particular configuration of the magnetic chains. Yet, the conjectural science proposed here was no longer the scientia experimentalis described in the Exercitationes, which denied to the human mind any access to the causes of things. In the Disquisitio metaphysica of 1641, Gassendi endorsed a conception of the scope of science that perfectly conformed to his new scientific practice. He declared science to be something more than a simple collection of sensible data and admitted the legitimacy of a process of inference that enabled the mind to proceed from known effects to possible causes.

In the Epistolae de motu, Gassendi even dared to expound Galileo’s proof of Earth’s motion based on the tidal phenomenon. Although he presented it as a faithful summary of someone else’s theory, he surreptitiously modified it so as to render it more compatible with the observed phenomena. Interestingly enough, a revised version of Galileo’s tidal theory is also found in the Syntagma, although Gassendi there officially adheres to Tycho Brahe’s cosmological system. To be sure, this adhesion represents a last-minute act of obedience to the Catholic Church. If one looks at the various drafts of the work, one sees that in 1642 (Ms. Tours 709) Gassendi presented Ptolemy’s and Copernicus’s as the only two possible world systems, and that in 1643 (Ms. Tours 710) he summarized Tycho’s proposal in merely ten lines. From the published version of the Syntagma, where attention is given to the Ptolemaic, Tychonic, and Copernican systems, it is still evident that Gassendi’s preference is for the latter, which is described as the most simple and elegant. But in two passages that were added to the manuscript at a late stage, the Tychonic cosmos is declared to be the only one capable of saving the phenomena while being compatible with sacred scriptures.

If in matters of cosmology Gassendi was ready to advocate the compromise favored by the church, he fought until the end of his life to demonstrate the compatibility between atomism and the Catholic faith. In a moment in which Jesuit natural philosophers were obliged to subscribe to the traditional Peripatetic theory of substance and accident as the only one that could explain the real presence of Christ in the Eucharist, Gassendi did not hesitate to get rid of substantial and accidental forms. To the Jesuit Le Cazre, who reminded him of the dangers that atomism posed to religion, Gassendi answered that tran-substantiation was a “supernatural process” that should and could not be explained in physical terms.

With extraordinary erudition and seemingly orthodox piety, Gassendi argued that Epicurus was, just like Aristotle, a pagan philosopher in need of mending. Epicurus had to be corrected in some crucial points, notably with respect to

  1. the creation and dissolution of the world and on the eternity of atoms;
  2. the infinite plurality of worlds;
  3. the blindness of causal necessity;
  4. the use of parts in living organisms; and
  5. the material and atomistic constitution of the soul.

But the fruits that could be obtained from a converted Epicurus were immensely more palatable than those gained from the Christianized Aristotle.



The Selected Works of Pierre Gassendi. Edited and translated by Craig Brush. Texts in Early Modern Philosophy. New York: Johnson Reprints, 1972.

Institutio Logica (1658). A Critical Edition with Translation and Introduction. Edited and translated by Howard Jones. Assen, Netherlands: Van Gorcum, 1981.

Descartes and His Contemporaries: Meditations, Objections, and Replies. Edited and translated by Marjorie Grene and Roger Ariew. Chicago: University of Chicago Press, 1995.

Pierre Gassendi (1592–1655): Lettres Latines. Edited and translated into French by Sylvie Taussig. Turnhout, Belgium: Brepols, 2004.


Alberti, Antonina. Sensazione e realtà. Epicuro e Gassendi. Florence, Italy: Olschki, 1988.

Ariotti, Pietro. “From the Top to the Foot of a Mast on a Moving Ship.” Annals of Science 28 (1972): 191–203.

Beaulieu, Armand. “L’enigmatique Gassendi: Prevot et savant.” La vie des sciences 9 (1992): 205–229.

Bernier et les gassendistes. Special issue of Corpus, edited by Sylvia Murr, 20–21 (1992): 47–64.

Brundell, Barry. Pierre Gassendi: From Aristotelianism to a New Natural Philosophy. Dordrecht, Netherlands: Reidel, 1987. The book describes Gassendi’s commitment to empiricism, Copernicanism, and Epicurean physics as being subordinated to the overall project of overthrowing Aristotle’s metaphysics and natural philosophy.

Clark, Joseph T. “Pierre Gassendi and the Physics of Galileo.” Isis 54 (1963): 352–370.

Clericuzio, Antonio. Elements, Principles and Corpuscles. A Study of Atomism and Chemistry in the Seventeenth Century. Dordrecht, Netherlands: Kluwer, 2000. The chapter on Pierre Gassendi (pp. 63–74) investigates the connection of atomism and chemistry in Gassendi’s thought.

Debus, Alan G. “Pierre Gassendi and His Scientific Expedition of 1640.” Archives internationales d’histoire des sciences 63 (1963): 133–134.

Descartes versus Gassendi. Special issue of Perspectives on Science, edited by Roger Ariew, 3 (1995): 425–581.

Detel, Wolfgang. “War Gassendi ein Empirist?” Studia leibnitiana 6 (1974): 178–221.

——. Scientia Rerum Natura Occultarum: Methodologische Studien zur Physik Pierre Gassendis. Berlin: De Gruyter, 1978.

——. “Scepticism and Scientific Method: The Case of Gassendi.” In Wissensideale und Wissenskulturen in der frühen Neuzeit; Ideals and Cultures of Knowledge in Early Modern Europe, edited by Wolfgang Detel and Claus Zittel. Berlin: Akademie Verlag, 2002.

Dumont, Simone, Jean Meeus, and Marcel Anstett. “Passage de Mercure devant le Soleil, observé par Gassendi (1592–1655), le 7 novembre 1631.” L’Astronomie 106, no. 4 (1992): 5–7.

Festa, Egidio. “Gassendi interprete di Cavalieri.” Giornale critico della filosofia italiana 71 (1992): 289–300.

Fisher, Saul. Pierre Gassendi’s Philosophy and Science. Leiden, Netherlands: Brill, 2005.

Galluzzi, Paolo. “Gassendi and l’Affaire Galilée of the Laws of Motion.” In Galileo in Context, edited by Jürgen Renn. Cambridge, U.K.: Cambridge University Press, 2001.

Gregory, Tullio. “Pierre Gassendi dans le quatrième centenarie de sa naissance.” Archives Internationales d’Histoire des Sciences 42 (1992): 203–226.

Hirai, Hiro. Le concept de semence dans les théories de la matière à la Renaissance. De Marsile Ficin à Pierre Gassendi. Turnhout, Belgium: Brepols, 2005. The concluding chapter (pp. 463–491) traces notably Gassendi’s debt to Petrus Severinus for the notion of seminal forces.

Jones, Howard. Pierre Gassendi (1592–1655): An Intellectual Biography. Nieuwkoop, Netherlands: B. de Graaf, 1981.

Joy, Lynn Sumida. Gassendi the Atomist: Advocate of History in an Age of Science. Cambridge, U.K.: Cambridge University Press, 1987. Joy argues that Gassendi’s atomistic natural philosophy was influenced and shaped by his historical researches. Lennon, Thomas L. The Battle of Gods and Giants: The Legacies of Descartes and Gassendi, 1655–1715. Princeton, NJ: Princeton University Press, 1993.

Lüthy, Christoph. Matter and Microscopes in the Seventeenth Century. PhD thesis, Harvard University, 1995. Describes (pp. 255–291) Gassendi’s microscopic research and its impact on his atomism.

Lüthy, Christoph, John E. Murdoch, and William R. Newman, eds. Late Medieval and Early Modern Corpuscular Matter Theories. Leiden, Netherlands: Brill, 2001. Contains the following chapters on Gassendi: Clericuzio, Antonio. “Gassendi, Charleton and Boyle on Matter and Motion,” pp. 467–482; Osler, Margaret. “How Mechanical Was the Mechanical Philosophy? Non-Epicurean Aspects of Gassendi’s Philosophy of Nature,” pp. 423–439; Palmerino, Carla Rita. “Galileo’s and Gassendi’s Solutions to the Rota Aristotelis Paradox: A Bridge between Matter and Motion Theories,” pp. 381–422.

Mazauric, Simone. Gassendi, Pascal, et la querelle du vide. Paris: Presses universitaires de France, 1998.

Messeri, Marco. Causa e Spiegazione: la Fisica di Pierre Gassendi. Milan, Italy: F. Angeli, 1985. Follows the parallel evolution of Gassendi’s epistemology and natural philosophy, through an analysis of his concepts of causality and explanation.

Murr, Sylvia, ed. Gassendi et L’Europe (1592–1792). Actes du colloque international de Paris, “Gassendi et sa postérité (1592–1792),” Sorbonne, 6–10 Octobre 1992. Paris: J. Vrin, 1997.

Osler, Margaret J. Divine Will and the Mechanical Philosophy: Gassendi and Descartes on Contingency and Necessity in the Created World. Cambridge, U.K.: Cambridge University Press, 1994. Osler argues that Gassendi’s probabilistic epistemology and his empiricist approach to science were deeply influenced by his voluntaristic theology.

Palmerino, Carla Rita. “Pierre Gassendi’s De philosophia Epicuri universe Rediscovered. New Perspectives on the Genesis of the Syntagma philosophicum.” Nuncius 14 (1999): 131–162.

——. “Gassendi’s Reinterpretation of the Galilean Theory of Tides.” Perspectives on Science 12 (2004): 212–237.

——. “Galileo’s Theories of Free Fall and Projectile Motion as Interpreted by Pierre Gassendi.” In The Reception of the Galilean Science of Motion in Seventeenth-Century Europe, edited by C. R. Palmerino and J. M. M. H. Thijssen, 137–164. Boston Studies in the Philosophy of Science, 239. Dordrecht, Netherlands: Kluwer, 2004.

Pancheri, Lillian U. “The Magnet, the Oyster, and the Ape, or Pierre Gassendi and the Principle of Plenitude.” Modern Schoolman 53 (1976): 141–150.

Pav, Peter Anton. “Gassendi’s Statement of the Principle of Inertia.” Isis 57 (1966): 24–34.

Popkin, Richard. The History of Scepticism: From Savonarola to Bayle. Rev. ed. Oxford: Oxford University Press, 2003.

Sarasohn, Lisa T. “Motion and Morality: Pierre Gassendi, Thomas Hobbes, and the Mechanical World View.” Journal of the History of Ideas 46 (1985): 363–379.

——. “French Reaction to the Condemnation of Galileo, 1632–1642.” Catholic Historical Review 74 (1988): 34–54.

——. Gassendi’s Ethics: Freedom in a Mechanistic Universe. Ithaca, NY: Cornell University Press, 1996. Examines how Gassendi made Epicurean ethics consonant with the new science and with the Christian notions of provindence and free will.

Société Scientifique et Littéraire des Alpes de Haute-Provence, ed. Quadricentenaire de la naissance de Pierre Gassendi, 1592–1992. Actes du Colloque International, Digne-les-Bains, 18–21 Mai 1992. 2 vols. Digne-les-Bains, France, 1994.

Taussig, Sylvie. Pierre Gassendi (1592–1655). Introduction à la vie savante. Turnhout, Belgium: Brepols, 2003.

Turner, Anthony, and Nadine Gomez, eds. Pierre Gassendi, explorateur des sciences. Catalogue de l’exposition, quatrième centenaire de la naissance de Pierre Gassendi. Digne-les-Bains, France: Musée de Digne, 1992.

van Helden, Albert. “Saturn and His Anses.” Journal for the History of Astronomy 5 (1974): 105–121.

——. “The Importance of the Transit of Mercury of 1631.” Journal for the History of Astronomy 7 (1976): 1–10.

Carla Rita Palmerino

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Gassendi, Pierre (1592–1655)


GASSENDI, PIERRE (15921655), French Catholic priest and philosopher. Born in Provence on 22 January 1592, Gassendi was admitted to the clerical state in 1604 and received his doctor of theology degree at the University of Avignon in 1614. He studied philosophy and theology at the college of Aix-en-Provence, where he later taught from 1616 to 1622. He published his first book, Exercitationes Paradoxicae adversus Aristoteleos, in 1624, a work in which he criticized Aristotelianism by using the skeptical arguments of the ancient philosopher Sextus Empiricus (fl. c. 200 C.E.). Having rejected Aristotelianism, Gassendi undertook the task of creating a new, complete philosophy, one that included the three traditional areas: logic, physics, and ethics. Writing in the style of the Renaissance humanists, Gassendi chose the ancient atomist and hedonist Epicurus (341271 b.c.e.) as his model. Before European intellectuals could accept the philosophy of Epicurus, it had to be purged of various heterodox notions, such as materialism and the denial of creation and providence.

Gassendi worked on his Epicurean project from the 1620s until his death. The massive, posthumous Syntagma Philosophicum (1658) is the culmination of this project. It consists of three parts: "The Logic," "The Physics," and "The Ethics." In "The Logic," Gassendi presented his theory of knowledge, which he had first articulated in the Exercitationes. His empiricist theory of knowledge was an outgrowth of his response to skepticism. Accepting the skeptical critique of sensory knowledge, he denied that we can have certain knowledge of the real essences of things. Rather than falling into skeptical despair, however, he argued that we can acquire knowledge of the way things appear to us. This "science of appearances" is based on sensory experience and can only attain probability. It can, nonetheless, provide knowledge useful for living in the world. Gassendi denied the existence of essences in either the Platonic or Aristotelian sense and identified himself as a nominalist.

In "The Physics," Gassendi presented a Christianized version of Epicurean atomism. Like Epicurus, he claimed that the physical world consists of indivisible atoms moving in void space. Unlike the ancient atomist, Gassendi argued that there exists only a finite, though very large, number of atoms, that God created these atoms, and that the resulting world is ruled by divine providence rather than blind chance. Deeply involved in the natural philosophy of his time, Gassendi tried to provide atomistic explanations of all the phenomena in the world, including the qualities of things, inanimate bodies, plants, and animals. In contrast to Epicurus's materialism, Gassendi enriched his atomism by arguing for the existence of an immaterial, immortal soul. He also believed in the existence of angels and demons. His theology was voluntarist, emphasizing God's freedom to impose his will on the creation.

Adopting the hedonistic ethics of Epicurus, which sought to maximize pleasure and minimize pain, Gassendi reinterpreted the concept of pleasure in a distinctly Christian way. He believed that God endowed humans with free will and an innate desire for pleasure. Thus, by utilizing the calculus of pleasure and pain and by exercising their ability to make free choices, they participate in God's providential plans for the creation. The greatest pleasure humans can attain is the beatific vision of God after death. Based on his hedonistic ethics, Gassendi's political philosophy was a theory of the social contract, a view that influenced the writings of Hobbes and Locke. His emphasis on free willboth human and divineled him to reject astrology, which he considered absurd, and other forms of divination that entailed any kind of hard determinism in the world.

Gassendi was an active participant in the philosophical and natural philosophical communities of his day. He corresponded with Galileo during his troubles with the church, and interacted with both Hobbes and Descartes. He conducted experiments on various topics in natural philosophy, wrote extensively about astronomy, corresponded with important natural philosophers, and wrote a treatise defending Galileo's new science of motion. Gassendi's version of the mechanical philosophy rivaled that of Descartes, with whom he engaged in an extensive controversy following the publication of the latter's Meditations in 1641.

Gassendi's philosophy was promulgated in England in several books published in the 1650s by Walter Charleton (16201707) and in France by François Bernier's Abrégé de la philosophie de Gassendi (1674). A younger generation of natural philosophers, including Robert Boyle (16271690) and Isaac Newton (16421727), who accepted the mechanical philosophy, faced a choice between Gassendi's atomism and Descartes's plenism. John Locke (16321704) absorbed many of Gassendi's ideas about epistemology and ethics, which thus had considerable influence on the subsequent development of empiricist epistemology and liberal political philosophy.

See also Aristotelianism ; Astronomy ; Boyle, Robert ; Cartesianism ; Charleton, Walter ; Descartes, René ; Determinism ; Empiricism ; Epistemology ; Free Will ; Galileo Galilei ; Hobbes, Thomas ; Humanists and Humanism ; Locke, John ; Logic ; Mechanism ; Natural Philosophy ; Neoplatonism ; Newton, Isaac ; Philosophy ; Physics ; Political Philosophy ; Reason ; Scientific Method ; Scientific Revolution ; Skepticism: Academic and Pyrrhonian .


Primary Sources

Gassendi, Pierre. Opera Omnia. Lyon, 1658; reprinted Stuttgart-Bad Canstatt, 1964.

. The Selected Works of Pierre Gassendi. Translated by Craig Brush. New York, 1972.

Secondary Sources

Osler, Margaret J. Divine Will and the Mechanical Philosophy: Gassendi and Descartes on Contingency and Necessity in the Created World. Cambridge, U.K., and New York, 1994.

Sarasohn, Lisa T. Gassendi's Ethics: Freedom in a Mechanistic Universe. Ithaca, N.Y., 1996.

Margaret J. Osler

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Gassendi, Pierre

Pierre Gassendi (pyĕr gäsäNdē´), 1592–1655, French philosopher and scientist. A teacher and priest, Gassendi taught at Digne, Aix, and the Royal College at Paris and held several church offices. He ranked with the leading mathematicians of his day. He violently opposed the authoritarianism of Aristotle, especially in the Exercitationes paradoxicae adversus Aristoteleos (1624). He revived and interpreted the atomic theory of Democritus and Epicurus in terms of the new science, thereby opposing the Cartesian school, and also attempted to reconcile atomism and Epicurean ethics with the teachings of the church.

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