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GASSENDI (GASSEND), PIERRE (b. Champtercier,
France, 22 January 1592; d. Paris, France, 24 October
1655), philosophy, astronomy, scholarship.
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 Cinquièmes 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
unalterable course 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
Collège 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