## 1. Historical Background and Gassendi's Life




Born in 1592 to a family of commoners in the tranquil Haute-Provence
town of Champtercier, Pierre Gassendi rose to become the greatest
Provencal scholar of his day, a member of the preeminent French
intellectual group of his times--the Mersenne circle--and
professor of mathematics at the College Royal. At an early age, his
instructors recognized great potential, and dispatched him at age
sixteen to Aix-en-Provence for studies of further sophistication than
his local schooling could provide. In these first years of scholarly
pursuit, Gassendi shuttled between Aix and Digne (the provincial
capital) and so began a life-long pattern of itinerant travel. His
extensive and early education vaulted him to professorship at Aix
while still in his mid-twenties. He shuttled between careers as well,
attaining success and station not only in academic circles but also in
the Catholic Church.




Gassendi's career as a priest is a crucial facet of his intellectual
constitution: his writings reflect an unbending allegiance to Holy
Scripture and Church teachings, though not necessarily in orthodox
doctrinal lights. He was ordained at the age of 24 or 25 and, while
there is no question of the strength of his faith, one motivation for
his career in the Church appears to be its provision of a sinecure.
Thus Gassendi started at the rank of a low-level local official
(Chanoine of the Cathedral) in Digne and rose to the rank of a
slightly higher-level local official (Prevot), still in
Digne, some twenty years later. Though he clearly pursued a studied
relationship with his higher authority, all the while he wrote letters
of support to the Church-embattled Galileo, sought appointment to the
secular College Royal, and cultivated deep personal and intellectual
ties with his non-Church patrons--the affluent
*fonctionnaire*, Francois Luillier; the Provencal
savant, Nicole-Pierre Fabri de Peiresc; the local count of Alais,
Louis Emmanuel de Valois; and the Parisian noble, Habert de
Montmor.




After some years of instructing pupils in philosophy and theology,
Gassendi distanced himself from what he believed to be rigid teachings
of the Scholastics in his *Exercitationes Paradoxicae* of 1624.
Thereafter he began a formative partnership in physiological,
astronomical, and historical studies with the wise and wealthy
Peiresc, summarized in Gassendi's glowing biography written upon
Peiresc's death in 1637. By this time, Gassendi had also developed his
early interests in a variety of questions in basic physics and in
restoring the philosophy of Epicurus--much as Thomas had restored
Aristotle, integrating his thought with what he held to be
theologically viable. His published work in philosophy and natural
philosophy captured the attention of the Minim priest, Marin
Mersenne. Gassendi spent the last two decades of his life traveling
back and forth between Provence and Paris because of varying
commitments to patrons, appointment to the College Royal, and
ill health. Throughout, he remained informed of and involved with
scholarly discussions of the day, owing to his engagement with the
group of philosophers and scientists united through correspondence
with Mersenne. In the Mersenne circle, debates ranged over numerous
topics central to the dismantling of Aristotelian and Scholastic
world-views, and Mersenne often used his role as facilitator to bring
together opponents on these issues. In that context, Mersenne helped
enable the entry of Gassendi's criticisms of Descartes's
*Meditations* into the *Objections and Replies*
(Gassendi subsequently published his rebuttals in his *Disquistio
Metaphysica* of 1646) and focused Gassendi's attention on refuting
the mystical attacks on Kepler by Robert Fludd (*Epistolica
Exercitatio, in qua principia philosophiae Roberti Fluddi medici
reteguntur*, 1630). Members of this circle regularly reported on
each other's experiments and proposed new challenges, such as
Poysson's well-known puzzling over whether physical indivisibles could
or should be identified with mathematical points. Gassendi used this
forum to learn about other empirical studies as well as to work out a
good many of his views.




His scientific career was varied and complex, if never quite
associated with glowing triumph. Some historians consider his greatest
accomplishment in this sphere to be his contribution to the revival of
ancient atomism but this represents only one end of his
anti-Aristotelian physics, and a small, albeit core element of his
scientific interests. His other accomplishments in physics includes a
study of bodies in free fall (closely modeled on Galileo's work), a
mature enunciation of the principle of inertia, and an early and
reasonably accurate interpretation of the Pascalian barometry
experiments of the late 1640s. Gassendi also ventured into
experimental science: he attempted to measure the speed of sound by
cannon fire, arranged to have weights dropped from the mast of a
moving ship to enact Galileo's thought experiment (and so dispel
doubts about the motion of the Earth), and conducted numerous chemical
trials involving, among other things, the dissolution of salts and
formation of crystals (which he took to bolster his molecular theory
of matter). These are only some of his better-known exploits. In
addition, he offered a wide variety of speculations on the earth
sciences based partly on geological fieldwork and biological and
physiological observations--and as shaped by his atomist
hypothesis. Finally, Gassendi devoted much of his time to astronomical
pursuits. He made regular observations of the skies for decades,
producing confirmatory evidence for Kepler's views, observing
sunspots, the anses of Saturn, and the passage of Mercury before the
Sun (1631), and successfully predicting an eclipse in 1654. Moreover,
he commissioned the first map of the moon, defended the Copernican
view as plausible save for its conflicts with Church teachings, and
offered many disparaging words on what he considered the scurrilous
and empirically intolerable practice of astrology.




In his final years, Gassendi relented to pressure from friends and
released a major portion of his Epicurean studies to the public,
publishing his Latin translation of Diogenes Laertiius's Book X on
Epicurus, along with ample commentary, in his *Animadversiones*
of 1649. He continued to work on this interpretive material, however,
steadily incorporating philosophical and scientific insights, until
his death in the Paris apartment of Montmor in 1655. Montmor, acting
as executor, collected this material in manuscript form and with
Gassendi's other Parisian friends arranged to have it published as the
posthumous *Syntagma Philosophicum*. The *Syntagma* is
more systematic than the *Animadversiones*, largely eschewing
the sometimes philological character of the earlier commentary and
principally discussing logic, the natural sciences, psychology, and
ethics from the perspective of what Gassendi deems philosophically,
historically, and theologically supportable. His interests in Epicurus
are ever-present, not least in the structure of the work, which is
divided into a Logic (including his textbook-format *Institutio
Logica*), Physics, and Ethics. Happily, we have a rather
well-rounded picture of Gassendi's intellectual pursuits, on top of
his Epicurean projects. Montmor and company had the good sense to
bundle the *Syntagma* together with the better part of
Gassendi's other writings (the *Animadversiones* notably
excepted) in six volumes of collected works, the *Opera Omnia*
(Lyon, 1658; Florence, 1727), which includes as well earlier letters
on optics and the free fall of bodies, a portion of his voluminous
astronomical observations, and a great deal of his correspondence.


(In what follows, we cite passages in *Opera Omnia* by using
the following abbreviations for the volumes: "O I", "O II",...,
"O VI".)



In the wake of Gassendi's death, his general renown, influence on
French schooling and popular conceptions of natural science, and
rivalry for Descartes' legacy, all grew. This impact was enhanced by
the 1674-1675 publication of a condensed, abridged, reorganized, and
occasionally paraphrased version of the *Opera Omnia*, written
in French by Gassendi's acolyte, Francois Bernier. Over the
following half century, the "Gassendistes" stood as
formidable opponents to the "Cartesiennes" in
French debates over educational and scientific matters, and Gassendi's
thinking spread--variously influencing Leibniz, Boyle, Locke, and
Newton, among others.


## 2. Method and Nature of Philosophical Inquiry




Commentators and historians conventionally designate Gassendi as an
early modern thinker yet there is good reason to at least consider his
work as belonging to the tail end of the preceding period. One facet
of his work that closely resembles Renaissance philosophy and science
is the historical focus of his method of inquiry. For almost every
philosophical issue Gassendi deems worthy of discussion, he first
introduces a wide range of previous competing views, beginning with
the antique schools, which he considers as 'live'
options. He engages with Aristotle and early (as well as late)
Aristotelianism, and allows great debts to Skeptic, Stoic, and
Epicurean thought. The history of philosophy is for him a source of
vitally important reasoning, the generally correct way to frame our
questions, and more occasionally, the answers to those questions. Thus
one principal attraction of atomism for Gassendi is that it suggests a
way to think about causation among material objects which he finds an
attractive alternative to Aristotelian views on one hand and
non-physicalist views on the other. In his theory of knowledge we find
one more instance of using ancient frameworks to model contemporary
problems: no criterion of truth, for example, is adequate unless it
satisfies the standard points made by the classical Skeptics. Some may
see this as evidence of Gassendi's modernism, but his broad concerns
with Skeptical thought certainly place him among good Renaissance
company. (The Skepticist and anti-Aristotelian strains of his
Exercitationes are also thought to be influenced by his reading of
near-contemporaries, including Juan Luis Vives and Pierre
Charron.)




Another Renaissance-type element of Gassendi's writings is his
stylistic obsession with antiquity. His Latin is learned if a bit
stultified, rife with quotations from Virgil, Horace, Cicero,
Tertullian, and others. An embroidered, ornate quality marks his few
extant French writings, too. He quotes frequently and liberally from
classical sources, usually in Latin though sometimes in Greek, and his
translation of Diogenes Laertius's Book X on the life of Epicurus is
the centerpiece of his 1649 *Animadversiones*. Gassendi does
not, as does Descartes, suggest his work is so modern as to have been
invented *de novo*. Rather, he constantly refers the reader to
a wide variety of other, generally classical writers as sources of
both like-minded and conflicting perspectives. Finally, the single
most time-consuming project of his career consists in his prodigious
efforts towards reviving the works and reputation of one particular
classical figure, Epicurus.




These Renaissance trappings notwithstanding, there are also at least
two reasons to think of Gassendi as very much among the moderns. For
one, he embraces the new empiricist's assessment of the old science:
what is wrong with the Aristotelians' physics is its routine
presentation, as well as grounding, in *apriori* theoretical
claims. He is not the only, or the first author of such a
view. Galileo breaks with tradition in distinguishing a science of
motion that, in principle at least, makes use of observation and
experiment. Bacon and Descartes, for their part, also counsel (to
varying degrees) a scientific method which builds on experiential
knowledge. But among the *savants* of the early seventeenth
century, only Gassendi, whose awareness of empiricism's roots and
implications is evident across his intellectual pursuits, integrates
philosophy and science on what he believes to be strictly empiricist
grounds. This integration is a natural consequence of his suggestion
that we gain all knowledge--outside of the theological--from
the senses.




A range of equally modern views follow from his proposed empiricist
foundations for the new science and its methods. He suggests a
probabilist notion of what counts as warranted empirical belief, and
insists that we may license beliefs about the sub- and
supra-perceivable but only if they are well-grounded in our beliefs
about the perceptually given. Further, he devises rules for accepting
or rejecting hypotheses, and guidelines for directing empirical
discoveries and our judgments of the same, where all such claims are
subject to the test of evidence from experiment or observation. It is
far from true that all, or even most, of his own claims about the
nature of the physical world meet this test, but the modernity of
Gassendi's philosophy and science lies in his proposal that this is a
goal to be set, altogether.


## 3. Refutations of Aristotelians and Descartes




For many commentators, Gassendi's empiricist theory of knowledge and
objections to Descartes's *Meditations* count as his paramount
philosophical contributions. In his core epistemology, he offers the
first modern model of knowledge from the senses to be integrated with
a physiological account of perception. In his objections to Descartes,
he rejects the clarity and distinctness criterion, seeks to undermine
the reasoning behind the *cogito*, and assails the ontological
argument. Each of these views represents a battle Gassendi has taken
up against the Aristotelian tradition or the Cartesian stance; his
thoroughgoing empiricism poses an alternative to both of these
competing perspectives.




One cornerstone of Gassendi's anti-Aristotelianism is the suggestion
that there is nothing necessary about the way the world is. God, he
proposes, could have made the world work in any number of ways, and
the contingent history and character of Creation means that there is
nothing immutable about the essence of a material thing. (That a
'substance', in either the Aristotelian or Cartesian
sense, might have an immutable essence, is a different matter, and
insofar as Gassendi has such a notion (for example, with respect to
space, time, matter, and void) he agrees that such things feature
unchangeable *sine qua non* characteristics.) Moreover,
Gassendi maintains, regardless of whether there are any essences and
whether they might be mutable, there are none to which we have any
epistemic access. The sole originating source of our knowledge is the
information the senses provide, such that what we know is closely
linked to what we can perceive. However, as Descartes notes, we can
perceive only appearances. Gassendi draws from this point the very
uncartesian lesson that appearances are all we can know about,
too--thereby ruling out knowledge of unperceivable essences. One
line of this reasoning can be found in his discussion of classical
skeptical tropes concerning the relativity of evidence from the senses
to individual experience--that honey tastes sweet to me, though
bitter to you; and that fire seems hot to us, though not so to insects
that live near fire (O III (*DM*) 388b; R 535). Since different
people have distinct experiences, our knowledge of honey's taste or
fire's heat differs from person to person and thus is not a reliable
guide to invariable characteristics of, for example, the honey or
fire. In cases like these we know a thing's qualities only as we
record them on a subjective basis. Such sensory information, based on
experiences which vary intersubjectively, cannot yield judgments about
a thing's qualities which do not vary in that (or any other)
way. Hence we lack knowledge of the thing's essence, if indeed there
is one. More broadly, from our principal source of ideas--the
senses--we know only how things appear to us (O III (*DM*)
311b-312a; R 184). (If we are to have knowledge of an object's
essence, Gassendi proposes, such requires a "perfect interior
examination" of that object, which is apparently not something
we may gain from empirical study.)




Gassendi also contests the Aristotelian view that we can know
universals, on the grounds that we cannot perceive anything more than
particulars in the world (O III (*Exercitationes*) 159a; EP
280-281). It follows, he suggests, that neither can there be any
universals we know about, at least with anything like certainty. Some
commentators (including Bloch, Rochot, and Osler) propose that
nominalism is a central Gassendist view, on the basis of this
rejection of essences and universals, as well as his epistemic
reliance on the apparent, and interest in signs and their conventional
character. But Gassendi's nominalism--if it be such, in the
orthodox sense--is intended less as an ontological assessment,
than as a statement of the limits of human mental capacity, whether
epistemic or linguistic.




Further building on the insistence that all knowledge comes from the
senses, Gassendi discusses the view (shared as well by Descartes and
the Aristotelians) that there are propositions we can know with
certainty. Since all propositions are judged as true or false on an
empirical basis, none can be deemed indubitable, save those of
theology and theologically-derived cosmology. This lack of certainty
extends as well to logical demonstration, whether of inductive or
deductive character. Nothing is certain about such demonstration,
Gassendi suggests, save the limits imposed upon it by the frailty of
human intellectual capacities. The natural bounds of our epistemic
grasp in the physical sciences, astronomy, or most any other field of
study is just what the senses tell us, plus any correctives reason
supplies on the basis of sensory-based knowledge we have already
accrued.




That Gassendi thinks there is a need for correctives on sensory
information makes clear the depths of his rejection of epistemic
foundationalism in Aristotelian or Cartesian thought: we cannot trust
even information from the senses to give us a failsafe picture of the
world. In this he embraces the Skeptical judgment that no source of
belief can provide for certain knowledge. Yet he cannot accept their
wholesale dismissal of sensory-derived evidence for belief. Knowledge
from the senses is possible just in case we have warrant for judgments
about appearances, though we may lack warrant for certainty about
those judgments. To the limited extent that we have the second sort of
warrant, he suggests, we find this in the reliability of our sensory
apparatuses (as he describes in his Epicurean-inspired account of
perception). We see here a 'constructive skepticist'
response to the Skeptics who say no knowledge is possible and to those
ancient and latter-day 'dogmatic' thinkers (including, in
his view, the Aristotelians and Descartes) who say knowledge involves
the attainment of certain belief--and is readily
attainable. While it may not be possible to have certain beliefs, it
is quite possible to have knowledge given that we construe it as
justified but less-than-certain belief. (Naturally, it must have a
veridical character as well, and Gassendi thinks it sufficient that
such beliefs are at least truth-resembling.)




Gassendi articulates such disagreements with Descartes in the
Objections, where he also rejects the Cartesian criterion of clarity
and distinctness, as either a standard for judging ideas or source of
epistemic warrant. As regards the former, Gassendi points out that
reason, which comprises our intellectual judgments and interpretations
of sensory information, is itself prone to error:



> 
> 
> ...although deception, or falsity, is not to be found in the
> senses themselves, which merely behave passively and only report
> things as they appear and as they must appear given their causes, it
> is to be found in the judgment, or mind, when it does not act with
> enough circumspection and does not perceive that things which are
> distant...appear more indistinct and smaller than they do close
> up.... (O III (*DM*) 388a; R 532; B 266-267)
> 
> 




If, for all their faults, claims based on sensory information are more
reliable than those based on reasoning (about sensory information or
anything else), then we ought not appeal to the latter as a basis for
judging among claims of the former. One reason he thinks sensory-based
claims are the more reliable of the two is that he takes the senses to
passively (hence steadily) collect information, in contrast to our
mental judgment actively (hence irregularly) organizing or relating
information. This is not to say that we will have no problems gauging
the warrant for claims based on sensory information as we collect
it. Rather, we will have even more problems in gauging claims based on
ideas about sensory information after such ideas are that much more
removed from a direct and perspicuous relationship to the world as
experienced, in our organizing and relating them to other ideas.




Moreover, the Cartesian criterion is irrelevant to judging cases of
empirical knowledge, Gassendi suggests--and even if this
criterion were not irrelevant, Descartes's own claims to knowledge
should fail all the same. First, in the case of empirical knowledge,
Gassendi proposes that the Cartesian criterion fails on classical
Skeptical grounds: it is possible for us to have ideas from the senses
we take to be clear and distinct which are nevertheless not the basis
for warranted claims to empirical knowledge of a general
nature. Though we may have clear and distinct ideas about the
appearances of, for example, the color of the sky we perceive, we
cannot infer from this clarity and distinctness that we know what
color the sky is. As the Skeptics warn, the sky could appear to
different persons in different colors, and as Gassendi adds, our ideas
of such an appearance could each be clear and distinct (O III
(*DM*) 314b; R 198-199). Second, knowledge claims Descartes
takes to be demonstrated by reason alone Gassendi dismisses as anyway
failing the proposed criterion; they are partial and confused, he
suggests, because they lack the immediacy characteristic of judgments
we attain by strictly empirical means. Whereas ideas we gain from the
senses directly represent worldly objects and events, ideas we attain
by deductive proof are but hypothetical analogues to such
sensory-derived ideas:



> 
> 
> ...it is not the same thing for us to conceive something by a
> veritable idea or a true image, and to conceive that thing by a
> conclusion that follows necessarily from an anterior hypothesis. In
> the first case in effect we conceive of the thing as absolutely so; in
> the second, that it should be some such thing; and also in the first
> case we know the thing distinctly and as it is in itself, and in the
> second case we know it only in a confused manner and by analogy, that
> is, in referring to it as something that must be known by way of some
> idea (O III *DM*) 322b; R 234).
> 
> 




In brief, our reasoned claims are less than fully clear or distinct
because we arrive at them through the mediation of ideas about our
empirical knowledge. Hence Descartes's most cherished claims about
essential properties of mind, God, and matter fail his own criterion
for lack of direct foundation in our ideas from the senses.




Not all of Gassendi's criticisms of the Cartesian criterion are rooted
in his advocacy of knowledge from the senses. Thus, he suggests, one
other problem with that criterion is its failure to make good on its
foundationalist promise. Just in case some of our clear and distinct
ideas turn out to be wrong, we will require some further criterion to
distinguish them from the correct ideas. And if the new criterion is
simply something like 'more clear and more distinct', then
we are on the road to infinitely many higher-order criteria, which
defeats the aims of the foundationalist project altogether. Finally,
Gassendi offers what Descartes himself came to call "the
objection of objections." Our ideas being clear and distinct
ideas is perfectly consonant with a solipsistic perspective, but then
the only thing we can know with certainty is our own thoughts. Yet a
viable criterion should (a) also distinguish our knowledge claims
about the external world, and (b) mark solipsistic claims as dubitable
to begin with. On top of these objections, Gassendi proposes that
Descartes has put the cart before the horse by suggesting we can
readily recognize what is clear and distinct and use this as a guide
to what is indubitable when what we need in the first place is some
guide as to what is clear and distinct:



> 
> 
> ...the difficulty is not, as it seems, to know if one must
> conceive things clearly and distinctly so as not to be mistaken at
> all, but to know by what way or method it is possible to recognize
> that one has a conception so clear and so distinct that it is true and
> impossible that we are mistaken. (O III (*DM*) 372b; R 458)
> 
> 




Another well-known set of Gassendi's objections target Descartes'
views of mind and body. One such objection is a prelude to the
well-known puzzle over how mind and body could be thought to interact,
posed by Princess Elisabeth of Bohemia. Gassendi wonders how Descartes
could take the mind to be thinking substance lacking extension yet
claim that it is somehow attached to the body, given that anything
joined to a body must itself be extended (O III (*DM*)
399b-401a; R 584-590). Descartes's answer is that he does not take
mind and body to be attached, which response immediately invites
Princess Elisabeth's puzzle.




In a related vein, Descartes's *cogito* reasoning also
undergoes close scrutiny. Gassendi understands this reasoning as one
person's inference from his or her indubitable recognition of
cognitive activity, to the claim that he or she exists as the selfsame
seat of such activity. Against such an inference he points out that
recognition that one has a set of thoughts does not imply that one is
a particular thinker or another. Were we to move from the observation
that there is thinking occurring to the attribution of this thinking
to a particular agent, we would simply assume what we set out to
prove, namely, that there exists a particular person endowed with the
capacity for thought (O III (*DM*) 289a-290a; R
82-86). Descartes is in dangerous waters at this point, for if indeed
the only claim that is indubitable here is the agent-independent claim
that there is cognitive activity present, then he can be fairly
associated with Averroist panpsychism, and its considerable taint. At
a minimum, the argument requires a significant leap of reasoning, and
for Gassendi, this is further evidence that Descartes places
altogether too much faith in his criterion and the work he thinks it
can do.




That Gassendi is primarily concerned here with the character of
Descartes's reasoning is plain enough: in the end and broadly
speaking, the two are actually close in their views about mind and
body. They are both dualists of one stripe or another, and the
particulars of Gassendi's physically-rooted psychology are reasonably
similar to those of Descartes's model. Gassendi's model of the mind
is often taken to be wholly materialist in design, particularly as
seen through the prism of his critique of Descartes. Yet only one
facet of the Gassendist soul is the material anima, the locus of
physically-determined pleasure and pain. He also posits an immaterial
animus, the seat of the intellect or rational understanding. This
cognitive faculty is the locus of spiritually-determined pleasures and
pains we associate with, for example, love of God or fear of
evil. Here we have an echo of the Thomist interpretation of De Anima,
according to which vegetative and motive facets of the soul perish
with the body though an intellective facet lives on forever.




Elsewhere on a theological plane, Gassendi shares other core views
with Descartes, though some commentators have tried to paint Gassendi
as concealing atheist tendencies, owing to his suspected materialist
and libertine allegiances. Such a charge is inaccurate. Yet it is
also so that Gassendi does not accept the Cartesian route to belief in
the Divine, notably rejecting Descartes' version of the ontological
argument.




The Cartesian version of Anselm's traditional argument suggests that
God has the intrinsic property of existence as part of a divine
essence, in the same way a triangle has intrinsic properties such as
having three internal angles summing to 180 degrees. Further, as with
all divinely-held properties, God has that existence property as a
perfection--that is, God exists in a perfect way, such that God
cannot not exist. Gassendi rejects this reasoning on two grounds.
First, we have no irrefutable intuitions of essences, whether such are
supposed to be represented by properties of triangles or of God.
Descartes' particular misstep here is to suggest that we may move from
the definition of God (which we intuit as a clear and distinct notion)
as essentially entailing the property of existence, to the view that
there is such a thing as God with said property. A definition of a
thing as having such and such properties does not commit us to the
thing existing with those properties, even if one of those properties
is said to be existence. This much was noted in Gaunilo's early
criticism of Anselm's version. Yet the more general point Gassendi
makes is that no intuitions untested by sensory experience will yield
knowledge of God's essence or anything else, as the primary mode of
attaining knowledge (and that by which any intuitions must be tested)
is empirical demonstration. Second, presaging the Kantian criticism,
existence is neither a perfection nor any sort of property or
predicate of things that exist. Rather, existence is simply an aspect
of things that exist, the mode or state of being that describes its
existing. Existence is accordingly a precondition for bearing
perfections (and for perfections being borne by the thing), rather
than something which itself can be a perfection. If we refer to a
thing's existence, we are only referring to a fact about the thing,
that it exists. Rejecting the ontological argument, then, eliminates a
sort of conceptual confusion: although we might think of perfections
existing (in a thing), it is hard to conceive of what it would mean
for existence to exist (in a thing), or for that matter, to not
exist. Along similar lines, there is no reason to accept the
underlying claim of the ontological argument that things which do not
exist are either imperfect or lacking in any way (O III (*DM*)
379b-380b; R 490-6).


## 4. Empiricism and Scientific Method




Another significant difference between Cartesian and Gassendist views
of God is that for the latter there is no divine epistemic
guarantor--indeed, for Gassendi, there is no absolute or
necessary guarantee on our epistemic access altogether. There is only
the contingent warrant of the senses. In the textbook account of the
early modern debate among empiricists and rationalists, Gassendi plays
a bit part in promoting the senses as the ultimate source of our
worldly knowledge. His views are painted as a vanguard but ultimately
inconsequential Continental counter to Descartes and as a slight
influence on Locke's more 'mature' empiricism. Gassendi's
contribution is more noteworthy than all that, however. His theory of
knowledge explicitly addresses historical traditions in epistemology,
develops a proto-reliabilist theory of epistemic warrant, wrestles
with timeless difficulties of empiricism, and forms the basis of a set
of allied views on the nature of scientific investigation.




The need for a theory of empirical knowledge in Gassendi's view stems
from the inadequacy of past and contemporary responses to the
Skeptics, whose puzzles he finds particularly compelling in the form
of the tropes as presented by Sextus Empiricus. The Skeptical tropes
call our attention to the general problem of whether, given the
fallibility of the senses, *any* knowledge is possible and in
what the warrant for such would consist. Gassendi turns the problem
around, limiting its scope to finding warrant for empirical knowledge
and declaring the special solution to resolve the general case. His
significant move in this regard is to propose, against the Stoics
(and, as we have seen, Descartes), that it is not a necessary
condition of our knowing some claim that we be certain of it. This
probabilism immediately broadens the range of what we can know through
the senses--as does his suggestion that we include among such
claims to knowledge those assertions about what may be hidden to the
senses yet legitimately inferred from evidence of the perceptually
given. This is his theory of sign-based inference, which suggests such
inferences are legitimate just in case they would be agreed to by a
great enough number of experts giving testimony--or else would be
false only on pain of contradiction.




Following an Epicurean, physicalist model, Gassendi recommends that
Skeptical worries are satisfied by truth-criteria and elements of
epistemic warrant rooted in the regularity and reliability of our
sensory perception and formation of ideas. Trustworthy evidence from
the senses yields warrant for empirical beliefs, albeit without
certainty and just in case the evidence for them does not conflict
with accepted evidentiary experiences. These claims are built upon the
proposals that sensory information has a material form (in the case of
vision, Gassendi promotes an atomist theory of effluxions bearing
images or light from the viewed object to the viewer), that the mind
receives sensory information through a wholly physical process, and
that some cognitive faculties dependably allow us to detect truth
properties of the objects of knowledge. The physical process
underlying this perceptual account is inspired by Epicurus but the
physiological details, optics of light transmission, and
epistemological lessons are strictly Gassendi's own. Indeed, this
account of justification marks him not merely as a proponent of a
causal theory (as may be said of Descartes, relative to the divine
epistemic guarantor) but as an early champion of a reliabilist
approach to the causal processes, claiming them as the source of
epistemic warrant.




The negative side of Gassendi's theory of knowledge bows in the
direction of the classical Skeptics: we cannot be conclusively certain
about, nor find ultimate truths among, empirical beliefs. The positive
side rejects an absolute Skeptical doubt, however, suggesting that
empirical knowledge is possible because we can identify a range of
strengths that are normally associated with many beliefs about
appearances--their reliability, approximation to the truth, and
likelihood by degrees. This approach--what Popkin calls the
*via media* of Gassendi, the 'constructive'
skepticist--suggests a practicable if approximate understanding
of the world is within our grasp.




This adumbrated version of empiricism is not without difficulties, as
Gassendi is first to recognize. For one, having extended the warrant
for the directly sensed to the indirectly sensed, we must find a way
to confidently adduce evidence on behalf of what appears before the
senses in indirect fashion only. For another, the supposition that
solving for empirical knowledge presents a solution for all knowledge
introduces the challenge of accounting for at least two apparent
counterintuitive instances--knowledge of abstracta and knowledge
of God and the cosmos (Gassendi subsumes the former to empirical
knowledge on proto-Millian grounds, but exempts most theological and
cosmological truth from empirical grasp (O II 398-424,
440-42)). Finally, he calls our attention to the recursive nature of
empiricist doubts. If a lack of adequate sensory data strips away
warrant for knowledge of the world then an empiricist theory of
knowledge must also appeal to what the senses tell us, about what we
can know of the world. The challenge, then, is to fashion an
empirically adequate theory of acquiring sensory data. In formulating
such an account, he anticipates crucial elements of later reliabilist
theories of warrant.




On the basis of these global views of knowledge in general, Gassendi
develops elements of a theory of knowledge and method specific to the
scientific endeavor. These elements include the proposal that we
attain and justify empirical claims with the greatest warrant by
deduction--yet those claims are at root probabilistic. He further
proposes that we maintain hypotheses as the basis of scientific
reasoning so long as there is empirical evidence for them, however
broadly construed. Taken together, these elements constitute a
commitment to a hypothetico-deductivism (H-D) which is characteristic
of some instances of actual scientific reasoning that Gassendi
discusses. This is not a typical or modern species of H-D method,
however, firmly wedded as it is to his empiricism. Indeed, Gassendi's
method cannot be adequately characterized in its entirety in this
fashion, given the several *other* forms of non-deductive
inference that he endorses or makes use of as fundamental to his
scientific method, including sign-based inference, analogous
reasoning, and inference to the best explanation.




A further element of Gassendi's scientific method consists in his
appeals to indirect evidence for claims about the unobservable, and
his willingness to count such evidence as adequate empirical grounds
for maintaining viable hypotheses. The most prominent instance of this
strategy is his embrace of an atomist matter theory as a 'most
likely hypothesis'. Of necessity, any evidence on behalf of this
hypothesis is to be found in the indirect form of
'indicative' signs--these are the surface level
phenomena for which he takes the existence of atoms to be a *sine
qua non* condition. A paramount instance of such evidence in his
view is what we may see through the microscope, when the visual
phenomena are explicable only given the existence of the
micro-structures we perceive--and in turn those are explicable
only in terms of yet smaller structures. Gassendi maintains that the
microscopic observations of crystalline formation and dissolution
demonstrate the molecular structure of matter, a key aspect of his
atomism. Equally innovative is his appeal to this putative source of
warrant in support of his matter theory.




Such arguments for atomism highlight Gassendi's anticipation of the
modern notion of inference to the best explanation (IBE) as a means of
judging among competing hypotheses. In advancing this strategy, he
emphasizes the capacity of a given hypothesis to account for a range
of different phenomena as a guide to the degree to which that
hypothesis approximates the truth. This strategy for justifying claims
about atoms also reaffirms his reliance on empirical data in seeking
confirmation of claims regarding the evident and nonevident
alike. While much is untenable or unlikely about these views, Gassendi
has at least offered a set of proposals towards resolving one of
empiricism's more vexing questions--how to transcend the bounds
of sensory data. We can know about unobservables like atoms, he
proposes, just in case our empiricism advances scientific knowledge
through hypothetical reasoning and warrants the sorts of inferences
about physical phenomena allowing for unseen features of the
world--for which the sensible features can provide evidence.


## 5. Atomist Matter Theory




The core of Gassendi's mature philosophy and natural philosophy is his
atomist matter theory. He initially borrows on historical atomist
sources--primarily Epicurus--but quickly integrates a range
of atomist claims into his proposed empirically defensible complex of
physical, metaphysical, and ethical perspectives. Some aspects of his
atomism fit poorly with the mechanical philosophy it is supposed to
exemplify. Yet Popkin is correct in suggesting that Gassendi's atomism
is a premier instance of his philosophical and scientific pursuits
constituting one and the same project. The putative empirical support
does not stand up to close inspection, and his particular brand of
this matter theory is inconsistent with other elements of the
mechanical philosophy. Nonetheless, his atomism provides an
innovative and consistent model for micro-level accounts of
macro-level physical structures and their behavior, throughout all
manner of natural, psychological, and social domains. In this last
regard, Gassendi's views resemble those of his acquaintance, Hobbes,
though with greater attention to core physical details of the matter
theory, and fine-grained notions as to how the micro-mechanisms may
operate.




Gassendi reveals atomist sympathies in his earliest works and
correspondence, where he rejects much of the style and some of the
substance of philosophy in the late Aristotelian tradition. Indeed,
some commentators see Gassendi as a thinker in the Renaissance mold
who simply lands on atomism as a central component of a broader
Epicurean alternative system to the robust range of received
Aristotelian views. However, though he shares most of Epicurus's
claims about atoms (and many Epicurean arguments for those claims),
Gassendi disagrees on key points. This suggests it is the merits of
the view itself, that it is the most likely physical hypothesis about
the underlying structure of matter, and not simply a general
restoration of Epicureanism, that leads him to atomism.




The broadest atomist claims Gassendi makes are rooted in his
background metaphysics and rejection of the infinite divisibility of
matter. He grounds the finer points of his atomism--regarding the
qualities of atoms and their aggregates--on observations,
experiment, and interpretations of the same, as well as his
assessments of alternative perspectives on matter theory. Following the
Epicurean model (with debts to Lucretius, Democritus, and others
still), he starts with a basic ontology of matter and void, and
develops a thoroughgoing account of the physical world rooted in a
picture of the inherent features of atoms. The general range of
phenomena and entities for which Gassendi offers atomist accounts owes
much to the ancients. Many of the particular explananda do not,
though, and a significant number of his explanatory arguments are his
own, at least in part.




Gassendi introduces notions of absolute space and time according to
which the universe is that which contains material Creation. In the
colloquial language of metaphysics, he lays out the 'floor
plan' of his picture of the universe in which he understands God
to place the 'furniture', namely, atoms and their
amalgams. Space, time, accident, and substance are the basic and real
(non-ideal) categories of existence: space and time are not modes of
substance (see section ten). 'Matter' refers to substance
that exists in space and time. Indeed, it is the sole and unchanging
stuff of physical things and so must exist as long as physical things
exist. Gassendi wants bits of matter to have their distinctive
qualities without the scholastic imposition of form. In particular, he
proposes, matter has essential and accidental qualities, though we can
only know the accidental ones, through experience.




As for the containing space in which atoms reside, Gassendi offers
empirical and apriori arguments on behalf of a void. He takes the
barometric experiments of his day, including his own at Toulon, to
demonstrate the existence of at least a partial, disseminated void.
Moving beyond such empirical argument, he echoes ancient atomists'
reasoning. Thus he rehearses the classical arguments that without
disseminated void between the parts of bodies, one cannot explain
division and separation of matter at the level of basic particles, and
that without the *inane coacervatum*, one cannot explain the
motion of bodies through space.




Both atoms and the void are for Gassendi
'principles'--by which he apparently means
'primary element', following a Scholastic tradition. It
does not follow from this, however, that they are both substantival in
his view. Whereas atoms are primary principles of material substance,
voids are non-substantival principles of separation in which bodies
are located, and by which they are separated and have their particular
sort of supra-atomic structure.




To establish that atoms are the primary principles or elements of
matter, Gassendi draws deeply on the well of ancient atomist argument.
This sort of 'historical evidence' or
'testimony' tolerably counts as one manner of support for
physical claims at the dawn of the early modern period. Given
Gassendi's pronounced empiricism, though, the degree of his reliance
on such testimony is surprising. He strikes an even more surprising
anti-empiricist chord in the introductory chapter of his Physics
(*Physicae Prooemium*), pondering a stipulative account of the
natural world that consists of the right physical postulates. In the
end, though, this approach is unacceptable for Gassendi, as such a
stipulative physics raises more questions than it answers. His
alternative tack is a series of reasoned defenses of basic atomist
tenets--frequently, amplifications and restatements of Epicurean
and Lucretian arguments--including claims as to the existence and
status of atoms as the primary material principles.




To take one example, Gassendi assumes material objects must have
*some* substratum composed of basic and indivisible elements
('principles'), and proposes that atoms, as the
*best* candidates for the role of substrata, are the material
principles in question. To arrive at this first assumption, he follows
Epicurus and Lucretius in adopting the Parmenidean dicta that nothing
comes from nothing and (conversely) that all matter must come from
something. He further embraces the ancient view that those dicta
entail a common substratum for all matter, as the composition and
resolution of material things always yield matter. To establish that
atoms are the best candidates for serving as this common substratum,
he reasons that *whatever* would serve as matter's substratum
cannot pass from existence. Moreover, elements of such substratum
would be incapable of passing from existence only if they were
indivisible and thus had no void--that is, were solid. Yet this
common substratum cannot be featureless, formless primary matter, as
the Aristotelians propose. It should have *some* identifiable
and unchanging features because such features are ineliminable from
matter. He concludes that all material objects must be composed of
elemental particles sharing the features essential to matter--and
the particles with those features just are atoms.




In a second line of Lucretian reasoning, Gassendi argues that atoms
are the primary principles of matter on the grounds that some
fundamental material elements must be impenetrable if we are to
account for varying degrees of resistance in macro-sized objects. He
suggests that since all material things resist pressure to some
extent, they all have one or another degree of solidity. The only way
to explain this range of solidity, or resistance to pressure, he
claims, is by supposing that the ultimate constituent elements of all
bodies are not soft, which is guaranteed if they are all
solid. Otherwise, there could be no bodies harder than the softest
ones, for if the ultimate constituent elements *were* soft,
then more solid bodies could never be composed from them. From this he
concludes that all material things must be composed of maximally hard
elements which, when put together with more empty space between them,
yield softer bodies--and, when put together with less empty space
between them, yield harder bodies.




As in the previous line of reasoning, Gassendi seeks to establish that
some properties of macro-sized objects--variable solidity here,
immutable materiality in his first argument--require an
underlying atomic architecture. Unfortunately, the atomic account
offered by the present argument also is not necessary to explaining
the macro-property--for we can still have diverse degrees of
resistance to pressure even if the basic elements of matter also range
in degrees of solidity. Worse still, this account is not even
sufficient to the task. Given that atomic size and the amount of
interparticulate void are also variable factors, different
combinations of these structural characteristics could yield identical
degrees of solidity across the otherwise very distinctive macro-level
objects they compose. Then varying atomic architectures is not
sufficient for varying degrees of resistance to pressure in objects on
the macro scale.




Such arguments and objections aside, Gassendi focuses his greatest
efforts to deny matter's infinite divisibility on the relevance of
mathematical and geometrical considerations to physical accounts of
matter's ultimate or near-ultimate particles. While acknowledging the
broad conceptual parellel between physical and mathematical continua
in ancient discussions (O I 262b), he warns against the mistaken
notion that physical magnitudes should be infinitely divisible just
because mathematical magnitudes are (O I 263b). This last observation
by itself fails to establish that atoms are actually divisible. Yet
Gassendi views this notion as the collapse of a major argument against
atomism. More generally, though, he is less swayed by any particular
arguments for or against atomism than he is by the merits and value of
taking atomism as a best working hypothesis, with which we may explain
a wide variety of shared properties among macro-sized objects--as
well as those properties that differentiate them.




A more fundamental task is the enumeration of atomic
properties. Gassendi distinguishes between two sorts: those properties
inherent in and essential to all individual atoms, and those which are
a feature of atoms in groups. His list of inherent atomic features,
which closely follows Epicurus's list, includes: extension, size
(*moles*, or more recognizably, *magnitudo*), shape
(*figura*), weight or mass (*pondus*), and solidity
(*soliditas*). Relative to each of these features all atoms
generally resemble one another, there being a limited range of sizes
and weights. One exception is shape. In order to account for
tremendous variety among natural objects, Gassendi claims, there must
be very many different types of atomic shapes (though not infinitely
so), and many tokens of each type (again, not infinitely so).




Another notable feature of this list of properties is that it signals
Gassendi's rejection of the cartesian view that extension is
sufficient to characterize what is essential to the least bit of
matter. Descartes is wrong, then, for the same reason that the
Scholastics are wrong to talk about featureless matter in the context
of physical theory. As Gassendi argues, while we might abstractly
conceive of matter with one feature such as extension (or none at all,
per the Scholastics), matter cannot actually come into existence
without the features that God assigns at Creation--namely, size,
shape, weight, and solidity.




The essential feature of atoms which does the most work in Gassendi's
physics--and also generates the most difficulties--is their
inherent weight, which gives them an intrinsic, natural
*tendency* to move. Given this tendency, atomic rest is either
provisionary or else an illusion. Atomic weight gives rise not only to
a simple capacity for constant motion, but also to a range of more
complex behaviors, enabling atoms to "...disentangle
themselves, to free themselves, to leap away [*prosiliendi*, to
spring out], to knock against other atoms, to turn them away
[*retundendi*, to check], to move away from them, and similarly
[they have] the capacity to take hold of each other, to attach
themselves to each other, to join together, to bind each other
fast..." Three other facets of atomic motion merit our
attention. First, it must be the general tendency of atoms to move in
straight lines given that the atoms here do not feature the
*clinamen*, or swerve (contrary to the Epicurean tradition,
though perhaps as Epicurus himself would say). Second, Gassendi
proposes that God endows atoms with a robust set of capacities for
moving themselves to varying degrees--leading some commentators
to see Gassendi as a vitalist or animist. Finally, Gassendi subscribes
to a seamless compositionality of matter and scalar invariance
regarding the nature and laws of motion, each of which lead him into
murky waters. On the micro-level, he is committed to a constancy of
motion that cannot be permanently arrested, whereas on the
macro-level, he holds that a principle of inertia governs the motion
and rest of all bodies.




Gassendi's compositionality thesis consists of the claim that the
varied combinations of atoms give rise to all manner of physical,
chemical, and biological features of the world and the phenomena they
exhibit. Two elements of this thesis are noteworthy. First, atoms
combine into particular molecular structures that correspond to
particular macro-level features and phenomena. This pre-Daltonian view
offers no suggestion that diverse collections of atoms are the source
of molecular variety. Yet this molecularism is novel all the same for
the broad suggestion that such micro-structures are intermediate-level
building blocks of macro-structures, and for the particular proposal
that the four Aristotelian basic elements be conceived of as molecular
aggregates. Second, molecular structures *en gros* behave in
the same ways as macro-level structures: they can be set in motion,
pulled, elongated, compressed, and so on. In the case of molecular
crystal structures, they can replicate, much as their macro-level
counterparts can. On the other hand, there are significant
dissimilarities among atoms and molecules: motion, density, and
elasticity are all points of difference, which suggest the difficulty
of a unified and internally consistent matter theory, relative to
physical norms or laws. Yet Gassendi is confident that, at least in
principle, the universe could have been created by God with any given
composition of particles, as varying in size, shape, or any other
dimension. This suggests that from that level of abstraction the laws
governing motion (not contingencies for Gassendi) are intended to be
scalar invariant. Even in cursory review, these tantalizing claims
suggest significant and controversial consequences of stipulating that
atoms have inherent weight and resulting tendencies to motion.




A further hallmark of Gassendi's atomic and molecular theories is his
suggestion, following the views of early atomists (prominently
Lucretius), that some atoms are endowed with greater activity than
others. The varied activity of such special atoms, or *semina
rerum*, gives rise to a differential dynamism in matter (of purely
materialist nature), allowing for special organic structures, as well
as growth of crystals. By contrast, neither atoms nor molecules are
endowed with powers *per se*. Nor do atoms bear forces, though
certain forces such as gravity can be explained by reference to the
behavior of atoms. Chemical forces, on the other hand, have molecular
explanations.




One of the greatest challenges to Gassendi's atomism from an internal
perspective is the seemingly quixotic nature of his search for
empirical foundations for atomism. In his era there is not the barest
hint of perceptually-derived knowledge of anything so small. There is,
he thinks, an empirically viable source of at least some claims
concerning atoms--the indirect data of indicative signs. Yet the
general tenor of his characterization and defense of physical atomism
signals a departure from his customary empiricism. As in his defense
of an indivisibility thesis, Gassendi relies foremost on reason, not
experience, to account for the origin and quantity of atoms and what
he takes to be their essential and inessential properties, their
internal impetus, motion, and causal role, and their contribution to
the motions and qualities we attribute to macrophysical objects. He is
hardly to be faulted in this regard given the lack of direct empirical
evidence available. Moreover, his responses to ancient and early
modern critics of atomism are firmly within *their* strategic
bounds, as they typically rely on reasoned argument without appeal to
empirical force.


## 6. Atomist Natural Philosophy




For Gassendi, the great promise of the atomist hypothesis is the
explanatory power across diverse domains of material phenomena (and
the great test, where feasible, is the gathering of empirical evidence
on behalf of that hypothesis). Gassendi's advance here is to develop
atomist accounts that are mechanically viable, where none previously
existed--whether because prior mechanical approaches were thought
inapplicable or because no solutions as such approaches yielded were
actually successful.




In what we today think of as chemistry and physics, Gassendi develops
a great range of applications for his atomist hypothesis. In his
optics, the atomist theory of light provides a counter to Descartes's
view of light as pressure. For Gassendi, light is a property carried
by particular atoms (*atomi lucificae*) that are identical with
heat atoms. These tend to travel at greater than average velocity
because they generally have fewer obstacles in their paths than most
atoms (O I 422a-432b). Sound, too, is particulate, and travels as such
particles travel. In contrast to a typical sound-wave view, the
surrounding medium does not play an important role: Gassendi takes the
velocity of sound particles, like that of light particles, to be
invariant with respect to the air or wind in which they travel. In an
experiment he models after a similar one of Mersenne's, he judges the
velocity of sound to be 1,473 ft/sec [478 meters/sec] (his
calculations are off by 435 ft/sec [146.7 meters/sec]) and invariant
to the pitch of the sound (O I 418a-419a). Even planetary motion has
an ultimately atomist explanation, as the underlying forces driving
the planets are magnetic forces borne by dedicated atoms (this is an
atomist modification of a view developed, though later abandoned, by
Kepler).




Gassendi's atomist accounts of chemical phenomena are equally
ambitious, suggesting among other things how vapors are created and
metals are soluble. Vapors are brought about by increases in the
distance between atoms in a liquid volume. Heat atoms remove some of
the atoms present in the volume, resulting in a greater percentage of
void and the matter taking the form of vapors (O I 398b-399a). As
concerns solubility, we account for *aqua regia* dissolving
gold, and *aqua fortis* dissolving silver, as a result of their
complementary atomic structures: gold atoms fit the pores of *aqua
regia* and silver atoms fit the pores of *aqua fortis* (O
II 33b ff, 39a-b).




In the realm of biological phenomena, Gassendi offers greatly diverse
accounts drawing on an atomist framework. His most significant
proposal in this regard is an account of generation and inheritance in
terms of a material 'soul' or *animula* bearing
ontogenetic information. In sexual reproduction, two sets of seminal
matter and corresponding animulae meet and jointly determine the
division, differentiation, and development of matter in the new
organism. The determination of inherited traits requires combining or
choosing among each parent's contributions, entailing competition and
dominance among the animulae (O II 284b-285a). The animula is defined
in terms of its constituent atoms, which must be uniform in order that
animulae may operate equivalently across different modes of
generation, whether 'pre-organized' or
spontaneous. Further, Gassendi offers his molecular model as a
material means of storing ontogenetic information received from the
souls of parent organisms (O II 170b-171a, 280b).




Rather more curious stories are found in his accounts of development,
physiology, and behavioral psychology. Thus, the root cause of
increased shellfish growth and marrow production during full moons is
increased humidity, stemming from the excitement of lunar moisture
corpuscles by sunlight. These corpuscles are then transported to the
Earth by rays from the sun reflected off the moon (O I 450a-451a). He
accounts for toxicological phenomena, such as the stunning capacity of
electric rays (*torpedine*), as emission of corpuscles with a
dulling power (O I 454b-455a). Other poisons provoke strange behavior,
such as those of the tarantula. These may work by producing activity
in the victim sympathetic to the attacker's activity, a result of
chemical alterations the poisons bring about in the victim's sensory
capacities and attunements (O I 456a). As concerns animal psychology,
Gassendi endorses Lucretius's suggestion (RN IV) that lions avoid
roosters at dawn because the latter can inject harmful corpuscles into
the former's eyes (O I 453b-454a). Sheep avoid unfamiliar wolves
because wolves emit corpuscles of an odor offensive to sheep (O I
456a).




As concerns human psychology, Gassendi offers a materialist (hence
ultimately atomist) account of the passions as a function of the
vegetative soul, including desire and fear, and motivating pleasure
and pain (O II 474f, 495f); these are ultimately governed, however, by
the rational and immaterial soul. There are, broadly, any number of
cognitive faculties and attributes that may be built out of or be
produced by atoms, Gassendi suggests, countering Lactantius's
complaint that the 'senses, thought, memory, the mind, genius,
[or] reason' cannot so be constructed. As with the passions,
though, there are limits. A viable atomist story can be told of
sensory phenomena and idea-formation though not reason and its allied
phenomena (O I 282b). Yet there is clearly some grey area, as memory
in particular seems open to a purely materialist account. Memory loss
results from a physical change in the brain resulting from
undernourishment; folds in brain matter preserve the physical
embodiment of memory, but a deficiency in nutrition leads to the
deterioration of those folds (O II 406b-407b; a similar Cartesian view
appears in the *Treatise on Man* (AT XI 177-178)).


## 7. Materialism, Libertinism, and Ethics




The thoroughgoing nature of Gassendi's atomism has led numerous
commentators from Descartes to Marx to view him as taking all worldly
structures and behaviors to be explicable by the interaction of
material bodies. According to this picture, Gassendi leaves little if
any room for the existence of non-material substance or its relevance
to metaphysical or natural accounts. One piece of putative evidence
for materialism in Gassendi's corpus is his extension of atomist
explanation, from all physical phenomena to a large range of
non-physical phenomena, including aspects of the mental, social, and
ethical. This is not entirely compelling, as we have seen that the
material underpinnings of our mental apparatuses is relevant to only
some portion of his psychology.




A second piece of suggestive evidence for Gassendi's materialism is
historiographical and rhetorical in character. Epicurus and Lucretius
were the great ancient materialists, Gassendi is their great early
modern exponent, hence Gassendi too was a materialist--his
Church-oriented misgivings notwithstanding. This thesis requires
thinking of Gassendi as holding closeted views relative to the Church
and Holy Writ, and indeed many of his views are highly nuanced in this
regard (q.v. his stance on Galileo). It is not clear, however, that
Gassendi intends anything other than a carefully delimited set of
accounts of materialist ilk, within what he considers to be the proper
realm of the physical. Strictly speaking, though, materialism is not a
doctrine by degrees, and that Gassendi's proposed realm of the
material extends beyond the reach of other, competing views of his
time does not make him a materialist in the pure sense.




A third piece of suggestive evidence was Gassendi's membership in the
group known as the *libertins* *erudits*. Other
members of this diverse group, on a broad construal, included Guy
Patin, Pierre Charron, Francois Le Vayer La Mothe, Gabriel
Naude, Theophile de Viau, and Cyrano de Bergerac.
Moliere is also sometimes considered to have belonged to the
*libertins*, and he is thought to have studied under Gassendi's
informal tutelage (Sortais 1922). Gassendi's ties to the
*libertins* also brought him in contact with a range of other
intellectuals and artists--the latter including, most notably,
Nicolas Poussin. The *libertins*, constituting more of a
literary salon than the philosophically- and scientifically-oriented
Mersenne circle, promoted a morality determined by reason, stripped of
theological considerations, and defined on an individualist basis. In
their commitment to intellectual liberty, they professed a diverse mix
of metaphysical and epistemic views, especially materialism,
skepticism, rationalism, deism, and Epicureanism--each party to
the group offering a different mix. They were politically and
socially savvy enough to promote their libertine views in a manner and
style that verges on the secretive. Such secrecy as a guiding
stylistic force can be seen in aspects of Gassendi's writing and
rhetorical style, as he frequently makes allusions likely to be
understood only by his friends or the equally erudite, constantly
draws on expressions from ancient sources to make his own points, and
offers a variety of quasi-coded rhetorical elements, most famously
including his somewhat hesitant and qualified endorsement of the
Copernican model.




Owing to their largely individualist conception of ethics--and in
keeping with late Renaissance tradition, the *libertins* tended
to avoid political theory and larger social issues, focusing instead
on self-governance and morality understood in terms of
character. Gassendi generally follows this conception in his ethics
(Sarasohn 1996), though he also outlines a broader political theory
(Paganini, 1989-1990). Aside from elements of his ethics and rhetoric,
it is an open question as to how much effect Gassendi's association
with the *libertins* had on his views--or for that matter,
how much influence he may have had on them. In one area in
particular--obeisance to the Church and its teachings--he
diverges significantly from his *libertin* counterparts.
Gassendi routinely emphasizes the sacred nature of Holy Writ and the
necessity (as well as benefits) of amending Epicurean thought to meet
strictures of accepted dogma. This adherence suggests that Gassendi's
interests in personal responsibility, empirical investigation, and the
underlying nature of matter did not signal a consummate atheistic
humanism, denial of spiritual activity, or materialism. If anything,
one might suppose that his innovative ethics, scientific method, and
physics were artificially constrained by his canonical beliefs. A more
accurate reading is that he trod a line between Church orthodoxies
and the most radical alternatives associated with the mechanical
philosophy and early modern ethics, such as we find in
Hobbes. Gassendi was a moderate modern thinker, promoting the new
against a background of opposition the potential of which he knew
quite well.




Though we lack grounds for calling Gassendi a complete materialist
moralist, a broad look at his ethics may suggest strong links to his
physics, in a Hobbesian manner (Sarasohn 1996). This parallel should
not be taken too far: Gassendi and Hobbes diverge in their views of
human agency and disagree about our unfettered, non-physically
determined capacity for moral deliberation. However, they each accept
that pleasure in some way motivates moral choice (though Gassendi also
makes allowance for the role of irrational appetite).




Indeed, insofar as Gassendi considers pleasure to be a
materially-realized phenomenon, he shares Hobbes's view of the morally
correct as something that can be defined in physical terms. However,
according to Gassendi and the lessons he draws from his Epicurean and
Stoic sources, any spirtually-related pleasure trumps any
materially-related one (O II 710a-b). The truest pleasures--hence
goods--are defined along the lines of Epicurean *ataraxia*
(attainment of tranquility) and Christian virtues, including in
particular love of God, and friendship and good will among
persons. The guarantee of our ability to seek tranquility or fulfill
these virtues is our free intellectual judgment
(*libertas*). Such a freedom consists in the ability of our
intellects to choose between good and evil, and this is turn yields
our capacity for volition, or free will (O II 821b-822b).




Free will and the ability to exercise conscience are also key concepts
underlying Gassendi's views on society and the body politic. Gassendi
agrees with Hobbes (and shares a Lucretian inspiration (Sarasohn
1996)) that individuals in a pre-social setting are motivated by fear
and desire for betterment, which leads them to join in a commonwealth
and concede at least some rights. For Hobbes, this motivation is
driven mechanically, and the commonwealth entails foregoing individual
rights in return for security. For Gassendi, on the other hand, the
motivation is driven by irreducible reasoned consideration, in favor
of the stability of social convention. Further, this social contract
leaves intact at least those freedoms and liberties which, to begin
with, figured in rational choice of the contract over the state of
individual insecurity. Gassendi veers from a strict physicalism,
proposing that societies are organized by social agreements chosen
through operations of the immaterial *animus* (O II 795a).


## 8. Space and Time




Even putting aside the framework of atoms and void, the Gassendist
ontology poses an alternative to rival Aristotelian and Cartesian
views, with respect to space and time. Gassendi's conception of time
and space is absolute. Time flows uniformly irrespective of any
motion, and space is uniformly extended regardless of any objects that
may be contained within it (O I 183, 285). Indeed, both space and time
pre-date Creation, and are infinite in character.




Gassendi borrows heavily on themes set out by earlier Italian space
and time theorists, including Campanella, Bruno, Telesio, and Patrizi.
One possible advance is suggested by his discussion of such an
ontology as a prelude to his matter theory: space and time are
pre-conditions for the existence of substance, rather than properties
of substances (as the Aristotelians would have it). In this regard,
Rochot (1971) proposes that Gassendi's ontology provides atoms as
stable entities and absolute space-time as a stable environment, which
together allow for a greater reliability of empirical data hence a
greater reliability of our data reception. The notion is that those data
have some fixity at the source, at least, given that the
space-time environment that contains material elements giving rise to
such data are unbended by relativistic position to anything else.
Naturally, such fixity would be only a necessary condition, and even
fails to provide guarantees at the level of basic sensory data, which
Gassendi recognizes in his discussion of the Skepticist tropes.




Gassendi's notion of non-relative space stands in direct
contrast to the Cartesian plenist account, which suggests that space
just is place, as defined by the extension of the resident (and
universal) matter. This contrast bears a clear result relative to
matter theory: Descartes is locked into a view of matter as infinitely
divisible, in order to account for the absence of void or, what amounts
to the same thing, the omnipresence of matter. Gassendi, on the other
hand, is free to pose the existence of atoms and the void, where matter
is located in space but is neither defined by nor definitive of that
space.


## 9. Logic




Broadly speaking, Gassendi expresses some three notions of logic in
the *Syntagma*. The first, enunciated in the history of logic
section that appears immediately prior to the *Institutio
Logica*, suggests a picture of logic along heuristic and didactic
lines, in the manner of Ramus, whose theory Gassendi lauds as a guide
to organizing and presenting existing knowledge (O I 59a-62b). The
second suggests that logic consists in the Aristotelian syllogistic,
the understanding thereof, and related methodological concerns. The
third suggests that logic consists in the study and use of causal
reasoning, and related methodological concerns--most notably
including an exposition of *regressus demonstrativa* theory in
the manner of Zabarella and Nifo (this notion expressly contradicts
his *Exercitationes* view that such causal reasoning cannot be
justified). These latter two notions yield the main thrust of the
*Institutio* (though the discussion of demonstration in Book IV
has clear Ramist debts). They also have great currency for Gassendi,
who typically crafts his use of syllogism and causal inference and
method after his *Institutio* conceptions, or at least signals
that he intends to do so. The same may not be said for his Ramist
conception. For although he makes ample use of rhetoric, he does not
turn to definition, distribution, or division for the purposes of
diagramming or expounding existing knowledge--per the logic of
Ramus--in any way that matches his interest in the traditionally
Aristotelian conception of analysis as problem-solving.




It has been suggested that a fourth notion--a psychologistic
account of cognitive operations, and perception in particular--is
a prominent goal of Gassendi's logic (Michael, 1997). While such
discussion forms part of the *Institutio* presentation, it is
by no means the main goal of the work or of Gassendi's conception of
logic. This can be seen from the thrust and length of his discussion
of the first three elements, and in particular syllogistic and causal
reasoning, and their attendant methodologies.


## 10. The Scientific Endeavor: Astronomy, Optics, and Mechanics




Gassendi's science is philosophically noteworthy in the way
that Descartes' or Kepler's science is, drawing on a robust
set of views on the nature of the world and what we know of it. His
scientific work in astronomy, optics, and mechanics is of particular
import in suggesting how we should pursue a purely empirical picture of
the world, within the limitations of our sensory access and the
constraints of tradition.




The principal elements of Gassendi's astronomy include a global
embrace of empirical method, advanced instrumentation, and
measurement, an interest in unusual celestial phenomena, and a
partially masked defense of Copernicanism. His embrace of an
empiricist astronomy can be gauged by his voluminous recorded
observations--some presumably with the telescope lenses sent by
his friend Galileo--carried out in concert with a league of
fellow observers strung across Europe and the Near East. A primary
goal of these recorded observations was to confirm and extend the
Rudolphine Tables, the project set up by Tycho Brahe and completed by
Kepler, to facilitate calculation of the planet's positions
(which goal in itself suggests Gassendi's adherence to a
Keplerian heliocentrism). Another facet of Gassendi's empiricist
astronomy was his denunciation of astrology as crafted independent of
any ideas from the senses, impervious to correction by experiment or
observation, and thus as failing to qualify as natural or experiential
knowledge. This view brought him into direct and bitter conflict with
Jean-Baptiste Morin, who also suspected Gassendi of an
arch-Copernicanism that was not only against Church teaching but would
obviate the astrological structures central to Morin's theories.
Gassendi's close interests in observation also led to employing
the *camera obscura* to gauge variations in the apparent
diameter of the moon--in accordance with its orbit of the Earth
and the apparent diameter of the Sun. Further, in his work with
Peiresc, Gassendi tackled the problem of determining longitude by
reference to lunar eclipses, later working towards this goal with
Claude Mellan on the first effort to chart the moon.




Gassendi's interests in unusual celestial phenomena dates back as
early as 1621, when he observed the colorful illumination of the sky
and dubbed these lights 'aurora borealis'. Based on his
correspondence with observers as far away as the Levant, he located
the source of the illumination at very high altitude, above the
Northern Polar region. In 1629, he observed the rare phenomenon of
*parhelia*, or false suns, which he explained in his Parhelia
seu soles..., in terms of the reflection of sunlight by ice or
snow crystals at high altitude. This account, shown to be accurate in
the nineteenth century, relies on the views of Gassendi and
Peiresc--based on their microscopical observations--that
crystal formations of snow and ice are highly reflective. The great
triumph of Gassendi's scanning of the skies was his observation of
Mercury's transit before the Sun (1631), the first such recorded
observation and a confirmation of Kepler's prediction of the planetary
orbits in accordance with the Three Laws. This confirmation in turn
enabled the subsequent calculations (Halley and Gallet, 1677) of the
distance between the Earth, the Sun, and the other planets.




The most controversial element of Gassendi's astronomy concerns
whether, and to what extent, he may be counted as a defender of
Galileo and the Copernican view. There is little question that he
sympathized with Galileo, and that he was fully aware of the merits of
Copernicanism, at times defending the view and some of its main planks
openly. Yet he was also clearly concerned with allegiance to Holy Writ
as interpreted by the Church, and to this end offers a Church-friendly
account of the condemnation that focuses not on the underlying
heliocentrism but on particularities of the Galilean model (O V 60b).
His considered judgment is that the Tychean model is preferable to the
Ptolemaic model, but also to the Copernican model--in the latter
case simply because the heliocentric picture does not fit with Church
teachings. He hastens to suggest, however, that those teachings are
themselves warranted by our own current empirical evidence--the
implication being that such truths and the concomitant rejection of
Copernicanism might well be revisable.




Closely related to Gassendi's interests in astronomy are a number of
issues in optics, where he sought to articulate a physiological model
of vision and a physical model of light. In so doing, Gassendi
contributed to early modern efforts that would eventuate in
distinguishing these two ends of traditional optics.




His integrated optics model follows an Epicurean and Lucretian
intromission view, that vision is a function of rays of light atoms or
image-bearing atoms that are received by our internal apparatus for
vision. The structure of this apparatus was of great concern to
Gassendi and his early collaborator on naturalist projects, Peiresc.
The premise of their work was that Kepler was largely correct in
postulating an optical image that gathers many rays into a coherent
representation in the eye, focused on the retina by the crystalline
lens. What troubled Gassendi and Peiresc, however, was the notion that
such an image as cast upon the retina would be inverted, leaving the
problem of identifying how we see the world as right-side up. Seeking
a physiological solution--as against any psychological capacity
that rights the inverted image--they suggested that the retina
itself acts as a mirror which rights the inverted image projected upon
it.




Another aspect of this integrated approach to optics was a reliance on
internal perceptual phenomena to account for external phenomena
regarding appearances, illusory or otherwise. This was not a
universally-held view, even in the age of the optics of light and
vision. In addition to Gassendi's interest in parhelia, he also sought
to explain apparent discrepancies in the size of the sun and moon at
different hours by reference to visual experience produced by light
phenomena (*De apparente magnitudine...*, 1642). Thus,
these bodies appear larger on the horizon than at their apogee because
the pupil dilates from the differential exposure to the light at the
horizon. (In fact, all such apparent differences are produced by the
distance effect of surface features of the area from which the
celestial body is viewed.) One key driver of such an appeal to the
interaction of light behavior and our visual apparatuses is Gassendi's
view that some explanatory role must be played here by the common
atomic structure underlying the images intromitted into our eyes and
the light rays cast by celestial bodies which are understood as
creating such images.




Gassendi's mechanics shows the strong influence of the Galilean
programme. He addresses the law of free-fall twice, first in a faulty
treatment in *De Motu* (1642), and next in corrected fashion in
*De proportione qua gravia decidentia accelerantur* (1646). In
the earlier work, Gassendi focuses on forces compelling the falling
body, which he takes to comprise the attractive force of magnetism and
the propelling force of air behind the falling body. This combination
of forces, he suggests, allows for the Galilean law that the distance
traveled by bodies in free-fall is proportional to the time of fall
squared. However, Gassendi mistakenly takes increases in velocity and
in distances to be equivalent, leading him to manufacture a false need
for greater velocity attained than what would be produced by the
attractive forces alone. In *De Proportione*, he acknowledges
this error, amends his calculations, and retreats to a causal account
that rests on the single force of the terrestrial magnetic
attraction. This is not one of Gassendi's empirical triumphs,
though--in neither work does he make any specific reference to
observations or experiments.




One notable success in the experimental domain is his performance of
the Galilean test of dropping a stone from the mast of a moving ship,
recorded in *De Motu*. Once dropped, Gassendi shows, the stone
conserves its horizontal speed (equal to that of the ship, before
being released) and its motion describes a parabola given its downward
fall. This result successfully refutes one simple anti-Copernican
argument, by showing that the Earth can move without superadding
motion to terrestrial objects otherwise in motion (which
superaddition, opponents of Copernicanism correctly maintained, would
generate much havoc in the motion of terrestrial objects). This much
Galileo surmised in his original thought experiment, though the
performance was excellent publicity for the Galilean perspective and
an opportunity for Gassendi to think through the issues at stake.




In this regard, Gassendi was able to take a step beyond Galileo's
conclusions, drawing from this test a generalized principle of inertia
(the Galilean version of inertia was fundamentally circular, given
that bodies in motion would trace the earth's curve). Gassendi saw
that the motion of the dropped stone at a sustained speed--in the
absence of any contrary force or obstacle--is an instance of
inertial motion, albeit one where the motion is compositional
(describing the parabola). Indeed, neither compositionality nor
directionality had any impact on inertial motion, Gassendi concluded:
any body set in motion in any direction continues, unless impeded, in
rectilinear path.




Other accomplishments in physics included a compelling measurement of
the speed of sound (showing that sound travels at the same speed, no
matter the nature of its pitch), and the first satisfactory
interpretation of the Pascalian barometry experiment. In his account
of the Puy-de-Dome experiment, Gassendi proposes that variations
in air pressure are relative to atmospheric conditions and altitude,
as the air is an elastic gas. He also suggests that this experiment
(which he repeats at Toulon in 1650) shows that created vacuum is
possible, at least as accumulated among part of the air particles in
the instrument 'sealed' by the mercury column in the
experimental apparatus. In establishing the elasticity of air as a gas
and accumulated void as a result of particle displacement, Gassendi
evokes his ontology of atoms and the void.


## 11. Impact and Influence




Gassendi's views were often transmitted in the early modern era
through the medium of Francois Bernier's
*Abrege* (1678/84), which work highlights the
atomist views and materialist tendencies of Gassendism. Such themes,
as well as empiricist threads of Gassendism, were attractive to a
number of late seventeenth century physicists and physicians
(viz. Nicholas de Blegny, Guy Patin, Antoine Menjot, and
Guillaume Lamy) and other philosophers (viz. Gilles de Launay), as
well as those among the Montmor circle or *libertins
erudits* (viz. Samuel Sorbiere, Jean Chapelain, and
Cyrano de Bergerac). Still others, especially Cartesians such as
Desgabets and Cordemoy, were rather distasteful of those themes, as
were hard-line theologians such as Louis Le Valois.




As Lennon (1993), Brockliss (1997), and others have noted,
Gassendi's overall influence in the French education system was
not a match for the Cartesian alternatives, and his views were
considered especially unworthy after his atomist views gained currency
in England.




The British success of Gassendism had three textual sources. In
addition to the *Opera Omnia* and Bernier's
*Abrege*, Walter Charleton produced a selective
and amended English translation of parts of the Animadversiones,
intermingled with other sources and his own perspectives (1654). There
was as well a group of atomist enthusiasts in the Newcastle Circle,
and a small existing British Epicurean club, whose members included
Kenelm Digby and Nathaniel Highmore. This backdrop of sympathetic
sources, not entirely faithful to the original, allowed a substantial
and diffuse influence of Gassendi's views in British thought. We see
Gassendism shaping the work of lesser figures such as Francis Glisson
(who embraced a *vis motrix*) and Thomas Willis (who crafted a
materialist theory of neural transmission based on Gassendi's view
(Wallace 2003)) but also such major thinkers as Boyle, Locke, Newton,
Hume, and Reid. Those sources of influence themselves were
sufficiently diffuse that it is difficult to make precise Gassendi's
imprint on these later authors, except where they explicitly
acknowledge their debts.




Boyle finds Gassendi's thinking agreeable in three respects. First,
he embraces Gassendi's criticism of Descartes' ontological argument as
rooted in an assumption as to the nature of God impervious to
proof. Second, he follows in the Gassendist model of placing
empiricism and experiment at the center of a viable scientific
method. Third, he praises Gassendi's corpuscularian theory as a worthy
ontology for the mechanical model of explanation, hastening to add
that further experimentation should give sufficient demonstration of
the verity of atomism. Indeed, he refuses to judge between the
Gassendist and Cartesian alternatives, presumably on the grounds that
we cannot produce evidence to decide the issue of matter's infinite
divisibility.




As Locke is concerned, it is by now well established that he may have
read Gassendi directly, and almost certainly read Bernier. The
evidence of influence shows up in some central Lockean theses: the
corpuscularian philosophy (here he follows Boyle as surely as he does
Gassendi), primary and secondary qualities distinction (a view also
held by Boyle, Descartes, Galileo, and others still), and broad
commitment to empiricism, including the negative thesis against innate
ideas and the positive thesis identifying sensory data as the primary
source of ideas. We also see Gassendi's likely inspiration in Locke's
probabilist embrace of an understanding of natural philosophy through
less-than-certain claims about the world, though his sub-par ranking
of 'sensitive apprehension' of the world is a rejection of
the Gassendist picture of sensory knowledge as the best for which we
might hope. Locke's theory of language, too, reveals Gassendi's
influence: the notion of nominal essences resonates with the proposal
in the Institutio Logica that the meaning of general terms is a
function of our sensory-based ideas, which contribute to our picture
of the properties we typically associate with the objects of those
terms. Finally, in regard to ethics, Locke offers a perfectly
Gassendist linkage between good and evil on the one hand and pleasure
and pain on the other, and like Gassendi celebrates the notion of
personal autonomy, though he locates the seat of moral judgment in
external norms (most prominently, the natural law) rather than any
internal ideals or virtues such as Gassendi upholds.




Newton reveals various interests in Gassendist themes, dating to an
early reading in his student days (see the *Trinity
Notebooks*). For one, he adopts the notion that Aristotelian
substance and accident fail to define all existents, and (along with
Barrow, who likely read Gassendi as well) suggests that absolute space
and time represent the fundamental ontological framework into which
matter and its phenomena are located. For another, he espouses a form
of the mechanical philosophy, albeit one that departs from orthodoxy
(as pronounced by Gassendi) in that God plays a significant and
sustained role in determining the course of natural phenomena. Here he
follows Gassendi's thought most closely in admitting atoms to his
ontology, nearly replicating Gassendi's list of atomic properties,
proposing that atomic structures yield chemical bonds that account for
the structures of larger bodies, and endorsing the Gassendist notion
of light as flowing in a stream of atoms (in opposition to the
Cartesian wave theory promoted by Hooke and Huygens). In the spirit
of Boyle, though, Newton tends to treat his matter theory as
instrumentally useful rather than as a universal hypothesis in search
of further instances. In this way he hopes to avoid the hard questions
about our ability to summon empirical verification of their existence
or precise character. One famous Newtonian methodological dictum
indicates there are aspects of atoms we can know, however. In the
*Principia* (1687), Newton suggests a transdictive principle of
Gassendist provenance (also embraced by Locke), according to which the
basic properties of bodies on the micro-scale ("the least
particles of all bodies") may be inferred from such properties
of bodies as we have evidence of, on the macro-scale.




Hume is less interested in affirming ontologies than in showing why we
have no good reason to invest belief in them, and accordingly picks up
on the rather different Gassendist theme of coming to terms with the
ancient Skeptics. His moderate or constructive skepticism
(*pace* Popkin) is founded on doubts concerning the possibility
of justified belief, focusing on the problem of induction as the great
difficulty undercutting our ability to know about the world. Lacking
rational justification, we simply fall back on induction as a
practicable means of grasping and managing our experience of events.
Here we see a striking similarity with Gassendi's
assessment--beginning with the observation that justifying any
generalization on particulars requires something beyond our cognitive
powers, namely, our empirical knowledge of all such particulars. From
this point, Hume draws the Gassendist lesson that induction cannot be
demonstrative, for lack of this generalization step or the supposition
"that apart from those enumerated there occurs none which is
different" (O I (*Institutio Logica*) 113a). Finally,
Hume's proposed resolution also resembles Gassendi's notion that we
might simply posit, as a matter of utility, the conformity of all
remaining unenumerated particulars.




Into the late eighteenth century, we see Gassendi's influence in
Reid's theory of external knowledge. This theory is centered on the
notion of what he calls 'suggestion', or the evincing in
us by our sensory data of concepts corresponding to the qualities of
things in the world. In its broad sense, 'suggestion'
consists in a signing relationship--as a matter of convention,
custom, or biology--between things or events in the world which
may be construed as signs (in the case of conventional signs, these
may be linguistic or symbolic entities) and what those things or
events signify. Here Reid draws on the long tradition of theories of
signs, likely relying in this instance on Gassendi in particular,
relative to the distinction between conventional
('artificial') and customary and biological
('natural').




Gassendi's influence spread further still, beyond Britain or the
modern era. The young Leibniz consciously followed Gassendi in
embracing atomism, later retaining high regard for mechanism but
abandoning the material model of substance in favor of the monadology
(Moll 1982). Christiaan Huygens pursued numerous Gassendist themes,
including anti-Aristotelianism, probabilism, a method of hypothesis,
and atomist matter theory. Gassendi's libertine, atomist, empiricist,
and quasi-heliocentrist views also met with keen interest further
afield, among like-minded philosophers and natural scientists in early
modern Poland, Italy, and Spain (Murr, 1997). In more recent times,
Gassendi would come to be seen as anticipating such notable views as
Mill's proposal that mathematical knowledge is empirical, and Popper's
notion that empirical falsifiability is a test of a hypothesis'
*prima facie* viability.


## 12. Recent Commentary on Gassendi




The precise place of Gassendi in the history of early modern
philosophy and science is only partly articulated by recent
scholarship, which has tended to focus on one aspect or another of his
thought, and to portray Gassendi primarily as an opponent of one or
another contemporary, to the neglect of his positive theses. The
laudable goal of such contextualist studies is to demonstrate his key
role in important debates of the era, yet the picture that emerges
from deliberation on these commentaries is rather Gassendi's relative
eclipse by other figures, notably Descartes. For example, one
historical approach (Brundell, 1987) highlights a strong
anti-Aristotelian strain which guides Gassendi's earlier criticisms of
the Scholastics as well as his later Epicurean works. From this
perspective, Gassendi may be seen as fighting the same battles as
Descartes, and losing in any such comparison because he engages his
foes with generally lesser flash and apparently less sophisticated, or
at least less novel, weaponry. Another common approach (Joy, 1987;
Darmon, 1998; Mazauric, 1998; Taussig, 2001 and 2003) is to emphasize
historicist and rhetorical elements of Gassendi's method, as employed
in his conversations and correspondence with members of the Mersenne
circle. Gassendi's role in that context was by no means marginal, and
it is impossible to downplay the centrality of that circle in early
modern scientific debate. Yet the most important figure to this group
was not actually an active participant in it, and this was
Descartes. Mersenne, of course, is the other core personality in this
context, and so Gassendi by default is at best a third. Gassendi
perhaps fares worst in comparison with Descartes in recent discussions
of their direct conflict over the *Meditations*, where
Gassendi's anti-Cartesian views are presented as a prism through which
we may best perceive the spectrum of his views (Osler 1994, Lennon
1993, Grene and Ariew 1995). There is undoubtedly a case to be made
that he represents the most prominent alternative to Descartes in his
times. However, highlighting this story encourages the view that
Gassendi deserves no more than footnote status and emphasizes, at
least historically speaking, his role as the *losing*
alternative.




Another fashion has it that Gassendi's doctrinal beliefs form the
foundation of, or otherwise influence, his philosophical and
scientific views. One such perspective suggests that his spiritual
concerns and materialist ontology jointly shape the character of his
metaphysics--leading to irresolvable internal conflict (Bloch
1971, Sortais 1922). Another perspective has it that his theological
views, and specifically his voluntarism, lead him to his empiricism
(Osler 1994, Sarasohn 1996). But it is not clear that Gassendi is best
understood as laboring in service of a doctrinal credo, or as
motivating his philosophical views by appeal to his theological
sensibility. He indeed tailors his Epicurean views to meet theological
constraints and endorses the only astronomical world-view he believes
acceptable to the Church, that of Tycho Brahe. Yet Gassendi's
definitive criterion for any physical, metaphysical, or
epistemological thesis is approximation to the truth, which is
empirically-determined. On the other hand, some theologically
inspired claims are woven into the fabric of his metaphysics and
psychology. For example, there are two souls, one sensitive and the
other spiritual, and the latter is required in order to satisfy
religious demands for an immortal unity attached to, but not
susceptible to the fate of, the material body. But in such cases
Gassendi is generally clear about non-philosophical motives,
introducing such corrections or additions to his reasoned or
empirically demonstrated views as are necessary by the dictates of
faith or Scripture. He frequently defends the primacy of Roman
Catholicism and faith over natural reason (O I 5a, O I 49a, O II
237a-b) yet easily distinguishes between objects of scientific and
theological investigation and reflection (O III (*De
Proportione*) 636a). To suggest that he arrives at the core tenets
of his metaphysics or epistemology in order to draw out the ultimate
consequences of his theology thereby misconstrues his broad
philosophical motives as well as his particular reflective and
investigative strategies.




By contrast, another element of recent scholarship highlights
Gassendi's philosophical motivations and strategies in *sensu
strictu*. In the years during and following the Second World War,
Bernard Rochot began this trend by bringing to light numerous
lesser-known texts as well as the manuscript background to Gassendist
atomism. More recently, Fred and Emily Michael have called attention
to empiricist sources and features of Gassendi's psychology and
epistemology. Others offering assessments of Gassendi's views in
similarly strict philosophical terms include Wolfgang Detel, Marco
Messeri, and Antonia LoLordo. In this interpretive tradition, Richard
Popkin elegantly poses the global character of the empiricism linking
Gassendist philosophy and science. Popkin (1967) ties together two
central facets of Gassendi's thought, proposing that the
'constructive skepticism' at the core of his epistemology
is an attempt (among other things) to show how to have an atomist
science--through inferences based on our data concerning
appearances.




The starting point of Gassendi's philosophy, in Popkin's view, is
skepticism about knowledge of essences, mitigated by allowance for
warranted beliefs about appearances and causal knowledge to which we
are entitled just because it helps us to make sense of beliefs about
appearances. Among the intriguing elements of Popkin's assessment is
the suggestion that Gassendi promotes an early prototype of inference
to the best explanation (IBE), defending atomism by appealing to its
explanatory value. Gassendi's strategy is a bit more complicated, for
he cannot grant that the evidence could be equally compelling for all
competing theses, given his view that atomism is the physical thesis
which best makes intelligible our experiential data to begin with. The
underlying methodological suggestion is that, in considering among
physical theses, the way we understand and interpret correlative data
about appearances may depend on which such thesis we are
entertaining. In calling attention to Gassendi's appeal to IBE, Popkin
identifies a principal challenge in binding together principal themes
of Gassendi's corpus, how to be an atomist and a thoroughgoing
empiricist at once (Fisher 2005).