## 1. Diderot's Life and Major Writings



Diderot's long, varied, and eventful life can be presented in
four distinct phases:


1. a period of maturation amidst struggle in the 1730s-40s as
the impoverished young Diderot sought to establish himself as a writer
in Old Regime Paris through the pursuit of the highly precarious
vocation of writing and publishing;
2. a period of intellectual ascent after 1749 as Diderot used the new
financial stability and intellectual notoriety acquired by editing the
*Encyclopedie* to build a base for his mature career as
an Enlightenment writer, critic, and *philosophe;*;
3. a period of intellectual celebrity as the new freedom brought
about by the completion of the *Encyclopedie* in 1765
allowed Diderot to produce some of his most important, if often
unpublished, work;
4. a twilight period begun in 1773 after his financial burdens were
fully eliminated through Empress Catherine the Great of Russia's
lucrative patronage, when Diderot brought to completion the wider
philosophical program established earlier, with an additional
dimension of political radicalism.


### 1.1 Years of Formation and Struggle (1713-1749)



Born to an artisan cutler in 1713 in Langres, a city 300 kilometers
southeast of Paris, Diderot began his life with very little pointing
him toward his future as a world-renowned writer and intellectual. His
first steps were supported by a university education under the
supervision of the Jesuits and training in scholastic philosophy and
theology through the M.A. level.



Having moved to Paris as a teenager to pursue his studies, Diderot
began to forge his career as a piece writer in the vibrant but
economically constrained world of Parisian publishing.
D'Alembert would later romanticize the life of the poor but
fully independent writer as an ideal to which all *honnetes
gens de lettres* should aspire, and Diderot actually lived the
impoverished bohemian writer's life in the flesh. During the
1730s, he struggled continuously to eke out a minimal existence
through occasional work with his pen, especially finding work as a
translator, and his financial hardship was increased after his
marriage in 1743 to an equally poor woman and the arrival of a
daughter soon thereafter.



In the 1740s, poor and still marginal, Diderot began to build the
career as a writer and intellectual that would make him famous. In
1742, he met the young Jean-Jacques Rousseau, a key moment in the
genesis of the *philosophe* movement, which Rousseau
immortalized for posterity in his *Confessions*. Etienne Bonnot
de Condillac also joined their circle at this time. Diderot further
began to write and publish his own books in this period, establishing
his name and reputation as a philosophical author, one who was
perennially associated with the most radical and controversial
ideas.



Key works from this period include a very loose translation of
Shaftesbury's *An Inquiry Concerning Virtue and Merit*,
in which Diderot turns moral sense theory into a kind of aesthetics of
Nature; *Pensees philosophiques*, a work of provocative
philosophical propositions concerning matter, motion, nature and
science; *La Promenade du sceptique*, a philosophical dialogue
which was written in this period but only published a century later;
and *Les Bijoux indiscrets*, which is best described as
philosophical pornography.



The climax of Diderot's prolific decade occurred in 1749 with
the publication of *Lettre sur les aveugles a l'usage
de ceux qui voient*, one of Diderot's masterpieces and
arguably his most sophisticated and complex philosophical text after
*Le Reve de D'Alembert* and *Le Neveu de
Rameau*. The *Lettre*, which presents itself as a series of
reflections on the blind mathematician Nicholas Saunderson, is perhaps
best described by Diderot biographer Arthur N. Wilson as
"disarming" (1972: 97).



Diderot's public intellectual acclaim increased with each of
these books, and by the time of the *Lettre sur les aveugles*
he had become famous enough for Voltaire himself, already the public
face of radical *philosophie*, to write to Diderot praising his
books. But the same acclaim that attracted Voltaire's attention
also rendered Diderot suspicious in the eyes of the French
authorities. A police file with Diderot's name on it was opened
soon after the *Pensees philosophiques* appeared, and
this work was ordered to be publicly burned in July 1746. By 1749, the
evidence pointing to Diderot's authorship of these subversive
(potentially or explicitly atheistic) works was conclusive, and after
the publication of the *Lettre sur les aveugles* an order was
issued ordering Diderot's incarceration in Vincennes prison. He
was imprisoned for three months starting in July 1749, before being
released the following November.


### 1.2 Ascendance as Writer and *Philosophe* through the *Encyclopedie* (1750-1765)



When Diderot was released from prison in November 1749, he was already
at work on a new project, the one that would launch him to global
intellectual fame.



Begun in 1745 as a project to publish a complete French translation of
Ephraim Chambers' 1728 *Cyclopedia, or Universal Dictionary
of Arts and Sciences*, the *Encyclopedie*, arguably
the single most transformative work of the French Enlightenment, had
become by 1749 something entirely new. Breaking free of the
translation agenda, a new work was imagined, to be edited by Diderot
and D'Alembert, that would serve as the vehicle promoting the
new *philosophie*.



In November 1750, Diderot released a "Prospectus" for the
*Encyclopedie*, inviting readers to subscribe to a new
multivolume compendium. In this preview, Diderot began to reveal his
conception of what the *Encyclopedie* would become. No
longer a translation of someone else's book, and even less a
staid compendium of already established learning, Diderot imagined the
*Encyclopedie* as a dynamic site of living thought, an
engine for changing, not codifying, existing knowledge. These ideas
were further developed in Diderot's article
"Encyclopedie", which was published in volume V of
the work in 1755.



The middle of the eighteenth century has appeared to many as a
watershed moment in French intellectual history. As a
nineteenth-century commentator put it, after this date "writings
hostile to religion appeared and multiplied, and a war broke out
between skepticism and faith" (Wilson 1972: 94-95, quoting
an editor of Barbier 1857: vol. 4, p. 378, fn. 1). Whatever the prior
preparation, the launch of the *Encyclopedie* at
precisely this moment fueled this dynamic, and it quickly provoked a
war between its editors and the religious authorities in France. At
the heart of the struggle were the Jesuits, especially
Guillaume-Francois Berthier, who used the Jesuit journal to
attack the new encyclopedia project and its editors. Diderot responded
with pamphlets, and this sparring continued as the first two volumes
of the *Encyclopedie* appeared in print.



The tension with French clerical authorities worsened when the
abbe de Prades, a friend of Diderot's and contributor to
the *Encyclopedie*--he wrote the entry
"Certitude"--successfully defended what was later
deemed to be a theologically suspect doctoral thesis. The controversy
led the crown to temporarily suspend the publication
*privilege* for the *Encyclopedie*, but
thanks to the favor that Diderot and his partners enjoyed in higher
places, publication was resumed and Volumes II-VI appeared
without pause between 1751-1756 even though accompanied by
ongoing criticism from the Jesuits.



New controversies over the *Encyclopedie* occurred in
1757, although the return of unrest had little overtly to do with
*philosophie*. The trigger was an attempt on King Louis
XV's life by a house servant named Damiens, who stabbed the king
with a small penknife. The act of regicide itself was less significant
for the *Encyclopedie* than the perceived motivation for
the crime, for authorities began to link Damiens's purported
madness to the unchecked spread of subversive *philosophie*.
Provoked by these public fears, French authorities issued new edicts
cracking down on allegedly subversive books, and new works critical of
the *Encyclopedie* also appeared, generating the idea of
an "Encyclopedist party" organized for the purpose of
attacking morality, religion and government. When Volume VII appeared
soon after Damiens's attack, the tinder was therefore set for a
new eruption of controversy.



The controversy grew intense, leading D'Alembert to resign as
editor, putting Diderot in sole control of the project. The final blow
against the *Encyclopedie* occurred in July 1758 when
Claude-Adrien Helvetius published *On the Mind* (*De
l'Esprit*), one of the most overtly materialist and
heterodox works of the French Enlightenment. Although Helvetius
was not technically an *encyclopediste*, he certainly
moved in the same circles, and his work fit comfortably with the
imaginary template of subversive materialist *philosophie* that
crystallized after the Damiens Affair. Accordingly, as the officials
in charge of securing public order, morality, and the book
trade--the three were one in absolutist France--began to
crack down on Helvetius and *De l'Esprit*, the
*Encyclopedie* found itself pulled into the courts as a
supposed accomplice aiding and abetting its crimes.



Thanks to a secretive ad hoc agreement, however, work on the final ten
volumes of the *Encyclopedie* was allowed to continue,
leading to the full publication of the work in 1765 with each of the
volumes falsely indicating a publication in Neuchatel as a way
of complying with the royal ban. During the same years, the volumes of
accompanying plates appeared since they were not subject to the ban,
and by 1772 the final volumes of the plates were published to
accompany the seventeen volumes of text that were already in print.
With that the entire *Encyclopedie* was brought to
completion.


### 1.3 The Years of Celebrity (1765-1773)



In 1765, after the final appearance of all text volumes of the
*Encyclopedie*, Diderot experienced a kind of liberation
as his life was freed from the work that had occupied most of his time
and energy over the previous fifteen years. During the 1760s, Diderot
continued to do what was necessary to see the
*Encyclopedie* project completed, ultimately authoring
nearly six thousand articles himself. But he was also gradually able
to step back, retreating in some respects to the background of the
*philosophe* movement. With this liberation, a highly
productive period in his life began as new and original books began to
flow from his pen.



Diderot's earliest writings from this period, pursued while the
*Encyclopedie* project was still ramping up to full
speed, continued the philosophical and literary explorations initiated
in the 1740s. Taken as a whole they reflect his lifelong preoccupation
with questions of life, liberty, purpose, and order within an
Epicurean cosmos that may not be governed by a providential creator,
along with his continuing interest in the epistemological problem of
discerning the nature and principles of such a world, especially as
they related to the emerging biological sciences of the eighteenth
century. Key works in this vein include *Lettre sur les sourds et
muets a l'usage de ceux qui entendent et qui
parlent*, a continuation of sorts to his *Lettre sur les
aveugles*, and *Pensees sur
l'interpretation de la nature*, a work that retains
the episodic, propositional structure of his *Pensees
philosophiques* while expanding the explanations within each
section.



Scholars have also suggested, though never proven definitively, that
Diderot contributed during these years to Baron
d'Holbach's *Systeme de la Nature*, first
published in 1770, a book that stands alongside
Helvetius' *De l'Esprit* as one of the great
masterpieces of French Enlightenment materialist philosophy. Diderot
was certainly at the center of the D'Holbach's coterie,
and if the dry and programmatic systematicity of
D'Holbach's book lacks the lively play of Diderot's
best philosophical writing, it is certain that he and the Baron were
kindred spirits.



One of Diderot's great masterpieces, written during these years
but only published posthumously, should be included as a part of the
natural-philosophical corpus summarized above, even if it engages with
these seminal questions of metaphysics and natural philosophy in an
overtly literary manner, drawing more on Enlightenment epistolary
novels and theater for its construction than the classical
philosophical genres of antique philosophy (although one should recall
that Plato wrote dialogues).



Called *Le Reve de D'Alembert*
(*D'Alembert's Dream*), the work is in fact a
trilogy of dialogues whose centerpiece provides the title. This
complex text reveals some of Diderot's most important thinking
about metaphysics as it relates to biology and the life sciences.
Although it was never published in Diderot's lifetime, it was
nevertheless one of his favorite works, and he gave one copy to
Catherine the Great as a gift, together, significantly in terms of his
understanding of the work, with a set of "Fragments" that
he presented as belonging to his physiological writings. The dialogues
would certainly have been considered a subversive work had they been
published when they were written, and whatever Diderot's
motivations in producing it as he did, the creative complexity
converges into what is without question one of the great masterpieces
of Enlightenment *philosophie*.



The same combination of literature and philosophy, textual play and
reasoned argumentation present in *Le Reve de
D'Alembert* is also present in Diderot's other
seemingly literary and artistic writings, which also contain much
serious science and philosophy.



One important cluster concerns the theory and practice of theater.
Diderot wrote scripts for plays that were staged in Paris, including
*Le Fils naturel* in 1757 and *Le pere de
famille* in 1758. These were moralizing melodramas advocating the
ethical value of the conjugal family and the virtues of thrift,
domestic love and piety. His plays are not major touchstones in the
history of theater, but his meta-theoretical writings about theater
itself, which provide many interesting points of departure for his
philosophy, are important contributions to aesthetic theory.
Diderot's novels and other works of overt fiction also partake
in the aesthetic explorations that mark his best work on the theater.
In both, Diderot manifests an interest in the nature and limits of
representation itself, and a self-aware consciousness regarding the
tenuous interaction between language, experience, and their ability to
merge (or not) into coherent representations. These are issues that
are present in all of Diderot's most sophisticated thought,
including his more explicitly framed philosophy.



Diderot displayed the same philosophical-literary tendencies in his
art criticism. His work in this area began in 1759 when the journalist
F.M. Grimm invited Diderot to contribute to his monthly journal
*Correspondence Litteraire* with reflections on the art
displayed at the biennial Parisian art salon. Staged in the Louvre,
these shows allowed painters and sculptors to showcase their work in a
setting that gave a broad public audience access to the work of the
best artists of the day. Others had written commentaries about the
exhibitions before, but no one before Diderot had provided anything
like the critical philosophical assessment of the art of the
salons.



A new academically centered art theory had developed in the
seventeenth century, and by 1700 it was joined by a new persona, the
connoisseur, who was helping collectors to hone their judgment when
separating truly great art from mere craft. The bi-annual Parisian
salons had already become a site of Enlightenment aesthetics and
connoisseurship by 1750, yet before Diderot no one had brought
together the job of the connoisseur and the aesthetician with that of
the public writer reflecting on art in relation to ordinary human
experience. In his "Salons", as they came to be called,
Diderot brought all of these agendas together into one discursive
program, inventing as a result a new identity: the art critic
sustained through contemporary art criticism. The result was also a
new and pioneering notion of philosophy of art.



Diderot's art criticism explored exactly the same dynamics
between form and content, author and interpreter, subject and
object--in short, the very problem of artistic representation
itself--that his theater, his fiction, and his philosophy
explored as well. The result was a general understanding of aesthetics
and its relationship to ethics that was integrally connected to his
philosophy overall.



Diderot's art criticism joined with his theater criticism, his
prose and other theoretical writings in offering readers reflections
on deep metaphysical and epistemological questions concerning the
power and limits of representation. From this perspective, it is
appropriate that arguably Diderot's greatest and most
influential text is at once a literary fiction, a
semi-autobiographical psychological memoir, a theatrical send-up of
Parisian society, an intimate portrait of contemporary social mores,
and a highly original and complex study of the nature of human
perception, being, and their interrelation.



Called *Le Neveu de Rameau*, the text ostensibly narrates
Diderot's meetings and conversation with the nephew of the
French composer Jean-Philippe Rameau. Yet the dialogue unfolds through
a back and forth between characters named "Moi" and
"Lui", or me and him, continually turning a discussion
between two discrete subjects into an inner monologue of one subject
dialoguing with himself. Indeed, as the exchange carries on, the two
characters are revealed to be different sides of a deep existential
dialectic. At this point the external reality of the characters begins
to dissolve, and "Moi" and "Lui" start to
become two competing principles within an intractable universal
ethical and metaphysical struggle.



Diderot did not publish *Le Neveu de Rameau* in his lifetime,
but the text found its way to Germany where it was read by Schiller
and Goethe. Goethe's German translation, published in 1805, was
a major influence on Hegel: the *Neveu* is the only modern work
explicitly cited in his 1807 *Phenomenology of Spirit*. Indeed,
its influence on the formation of Hegel's own dialectical
understanding of metaphysics and the nature of being is patent, and a
line connects Diderot and the *Neveu* with all subsequent
metaphysical understandings of the self as a singularity caught in a
constant struggle with universal forces pulling the unity of being
apart.


### 1.4 Twilight Years (1773-1784)



Further helping Diderot after 1765 was the generosity of Catherine the
Great of Russia, and his trip to her court in St. Petersburg in 1773
marks the passage of Diderot into the final stages of his career.



Catherine watched the development of the *Encyclopedie*
project with great interest and expressed affection for French
Enlightenment *philosophie* overall. Fate provided her with an
occasion to express her appreciation directly to Diderot when a
financial burden forced him to sell his library. Catherine made the
purchase, giving Diderot an annual pension in addition. This made him
a wealthy man for the rest of his life. Diderot traveled to St.
Petersburg to meet with Catherine in 1773-74, and this trip
marks his entrance into a leisured retirement in Paris where he
continued to write.



Diderot's last writings continued themes pursued throughout his
life, but one new interest was history. His *Essai sur les
regnes de Claude et de Neron*, which turned interest
in ethics and morality toward questions of politics, justice, and
history, was one result, as were his contributions to the final
edition of the abbe Raynal's massive, nineteen-volume
global history entitled *Histoire philosophique et politique des
etablissements et du commerce des Europeens dans les
deux Indes*.



The latter was produced by Raynal in a manner similar to the
*Encyclopedie*, with numerous authors contributing. The
resulting work was a pioneering world history defined by its argument
that the transformations triggered by the Colombian Encounter were the
decisive agent of world historical development. Diderot's
contributions included explorations of the role of commerce, conceived
as an autonomous natural-historical force, in the shaping of political
and social change, a theme that connects Diderot's writing with
the new sciences of Enlightenment political economy. The Atlantic
slave trade also attracted his attention, and some of his most
passionate contributions involve imagined dialogues about the horrors
of the European imperial slave system spoken by oppressed Africans.
Raynal's *Histoire* was a massive bestseller, translated
into many languages, and it was a direct influence on Hegel, Marx, and
through both on modern world history more generally. Diderot's
contribution to this influence was as important as any.



Diderot's contributions to Raynal's *Histoire* have
been described as proto-anthropological, and another provocative work
from these years, his *Supplement au voyage de
Bougainville*, was similarly conceived and influential. The text
offers an imagined dialogue between Tahitians and Europeans about the
different sexual, marital and familial mores of the two cultures, and
Diderot anticipates through fiction the figure of the native
ethnographer who asks comparative questions about the foundations of
morality and civilization so as to generate universal cultural
understandings through comparison.



In these texts, and others from these years such as his
*Observations sur le "Nakaz"*, a commentary on
Catherine's Enlightened reform program for Russia, Diderot
appears in a newly radical political guise as an aggressive
egalitarian and democrat who has little patience with traditional
justifications for hierarchy and top-down distributions of power. He
is also a passionate abolitionist with no tolerance for the crimes of
the Atlantic slave trade. Nature does not work through hierarchy,
Diderot insists in these texts, and connecting politics with his
natural philosophy he argues for a radical decentralization of
political authority, and a fully bottom-up, egalitarian understanding
of social order. These convictions are also manifest in his thinking
about race and slavery. He rejected altogether the new anthropology
promulgated by Kant and others that spoke of biologically and
civilizationally distinct races, offering instead a monogenetic
understanding of humanity where difference was a matter of degree
rather than kind. Diderot was by nature a writer and thinker, not a
political activist, and his political philosophy, while suggestive of
emerging radical political trends, appears as the least developed
aspect of his thought.



When revolution erupted in France in 1789, the memory of Voltaire and
Rousseau led to their inclusion in the pantheon of revolutionary
heroes worthy of immortal commemoration. Diderot, by contrast, was at
best forgotten and at worst treated as a figure hostile to the new
political movements afoot.



This combination of neglect and outright hostility pushed Diderot to
the margins of French culture in the nineteenth century, and it would
take another century before retrospective interest in his work would
be renewed. Too systematically committed to his materialism, too
vigorous in his irreligion, and too passionate and principled in his
embrace of egalitarianism and universal democracy to be acceptable to
anyone with the slightest worry about the rising tides of radical
socialism and materialist freethought, Diderot became a pariah for
many in nineteenth-century France and Europe. Only after 1870 was
interest in his work revived, thanks in part to the new editions of
his writings, which made him newly available to scholars and readers,
and to the changing cultural and political climate. Soviet Marxists,
for example, played a key role in reviving Diderot scholarship after
1900, and contemporary Diderot studies, which is thriving today, is
largely a twentieth-century creation. Literary scholars led the way in
establishing the contemporary scholarship, but recently scholars
attuned to the very different character of philosophy and science in
the eighteenth century have begun to return to Diderot's work,
finding in it the complex and sophisticated thinking that was his
hallmark.



Diderot is now actively studied by both literary scholars and
intellectual historians alike, and there was even a movement afoot as
recently as 2013 to enshrine Diderot alongside Rousseau, Voltaire, and
Condorcet in the Pantheon of French national heroes. Headlines
worrying about "*un homme dangereux au
Pantheon?*" revealed the continuing influence of his
alleged infamy, yet the twenty-first century may be the moment when
Diderot is finally recognized as the important eighteenth-century
philosopher that he was.



For a more complete biography of Diderot, see the
 Biographical Supplement.


## 2. Major Themes of Diderot's Philosophy



There are different ways of dividing up Diderot's intellectual
career, some which emphasize pure philosophical commitments, others
focusing on particular projects or strands of his thought, and still
others giving pride of place to politics. Of course, all of them
acknowledge the central place of the *Encyclopedie*, not
just because it was an enormous editorial project spanning many of the
"best" years of Diderot's productive life, but
because it marked the invention of a new model of knowledge,
collaborative in the literal sense as a compendium of individually
authored articles, but also in the sense of joining disciplines,
including the "arts and crafts", as newly equal purveyors
of theoretical knowledge along with "first philosophy".
The *Encyclopedie* is also an important resource if one
is looking for Diderot's sources, as he authored many long
entries on Epicureanism, Hobbes, Locke, Leibniz, or rather
Leibnizianism, along with texts on eclecticism, skepticism and other
doctrines which reveal both his involvement with such ideas and the
way he transforms them.


### 2.1 Skepticism, eclecticism and language



Aside from the early translation projects discussed in Part I,
Diderot's first philosophical writings, such as the
*Pensees philosophiques* (1746, expanded in 1762) and
the *Promenade du sceptique* (1747), play a complicated
rhetorical game with deism (rather than overt materialism),
skepticism, and natural religion. In the *Pensees*,
Diderot even toys with a "design argument" using the
classic example of the complexity of a butterfly's wing (SS
XVIII), although he seems to retract this a few years later, in the
*Apologie de l'Abbe de Prades* (1752), writing
that "I thought the wing of a butterfly brought me closer to
divinity than a volume of metaphysics" (DPV IV: 361,
translations always ours unless otherwise indicated). Even if he is
not yet a materialist in these works, Diderot does speak of the
necessity to "widen" or "enlarge" God
(*Pensees philosophiques*, SS XXVI), a phrase which
has fairly strong Spinozist and/or deist overtones.



By the time of the *Lettre sur les aveugles* (1749), Diderot
has launched upon a philosophical project, or a set of intersecting
projects, which will endure to the end of his life: a radicalization
of empiricism in the direction of a materialist metaphysics, which
also remains at times skeptical or at least anti-foundationalist with
regard both to the possibility of an intellectual system, and to the
existence of order or totality in the universe.



Yet if Diderot's philosophy needs to be understood in terms of
his lifelong project to develop and refine certain clear metaphysical
and epistemological commitments and arguments, it also needs be to
understood in terms of his avowed "eclecticism", in
particular his hostility to overly binary dogmatic thinking. This
reflects his deep awareness of the complexities of language itself,
especially the immanent tendency for speech to refute itself and
subvert its stated convictions. Diderot's passionate love for
irony, satire, humor, and the play of language as both a critical and
subversive force often served him as a vehicle for capturing the
infinite complexities of being that transcend stable finite human
understanding, which means we his writing should also be read with the
same attention to its linguistic complexity that he had when writing
it.



Although the link it is not often noted, it is useful in this context
to remember that Diderot was among the generation of French
philosophers that were directly influenced by Nicolas
 Malebranche,
 whose influence upon French philosophy in the years 1690-1730,
the precise years of Diderot's maturation as a thinker, was
immense and insufficiently recognized. This influence was not rooted
in Malebranche's specific doctrines such as occasionalism, but
in the model his philosophy offered of how empirical skepticism could
be sustained together with scientific, and especially mathematical
rationalism. Diderot's own affection for mathematics was rooted
in these Malebranchian currents of French thought, as were his strong
convictions about the limits of mathematics as well.



Malebranche's philosophy has aptly been described as
"Hume, but with Christian faith" in the sense that like
Hume he offers a massive skeptical critique of the capacity for humans
to produce certain knowledge as a result of the epistemological
inadequacy of their senses and higher cognitive faculties, but unlike
him Malebranche nevertheless offers a path forward toward such
knowledge through a Cartesian understanding of divine reason as
accessible to humans through the proper practice of mathematical
reasoning. In brief, to reason like God is to reason like an advanced
mathematician, especially one trained in the new analytical
mathematics of the period, and to the extent that this kind of
reasoning is adaptable to human language itself, it allows for human
thinking to connect with the divine order of things through a proper
practice of rigorous cognitive and linguistic discipline. Anchoring
this understanding for Malebranche was a Christian faith in a
rationally created cosmos accessible to the human mind, and while
later Malebranchians followed Hume in discarding this Christian
foundation, many nevertheless absorbed Malebranche's lessons
regarding the power of a properly constituted language (his model was
advanced analytical mathematics) to serve as a bridge connecting
limited humans with the infinitude of being. Diderot's partner
D'Alembert represented the explicitly mathematical strand of
this tradition of thinking, but Diderot embodied another strand, more
attentive to language in all its variety as the link joining finite
human understanding with the infinite complexities of nature. Although
Diderot was suspicious of D'Alembert's Malebranchian
conception of mathematics as the foundational model for all of
science, his own interests in the empirical natural sciences were
still rooted in the same preoccupation with how nature represents
itself and is represented by humans in scientific work. He was
especially attentive to the crucial role that language plays in
rendering experiential phenomena suitable for human knowledge, and if
he was critical of the over-emphasis upon mathematics as the supreme
model for a fully rigorous scientific language, he was nevertheless
Malebranchian in treating the relation between experiential phenomena,
linguistic description, and human knowledge in all its variety as the
epistemological zone that mattered most.



Diderot's eclecticism from this perspective was not simply a
negative reaction against dogmatism, even if in his important
*Encyclopedie* article "Eclectisme",
he opposes eclecticism to sectarianism. He also explicitly ties
eclecticism to an attention to language and discursivity in
philosophy. Founders of discursivity are eclectics, distinct from
syncretists (Diderot mentions Luther and Bruno as examples). However,
he fully disapproves of the Alexandrian school of eclectics, while
attaching himself to *modern* eclecticism (including
Campanella, Hobbes, and Bacon, but also Descartes, a reference that
makes most sense if read through Malebranchian Cartesianism):
"The eclectic does not randomly gather together truths, nor
leave them in isolation; even less does she force them into some
determinate plan" (*Enc.* V: 270). Diderot presents both
Bacon and Descartes as eclectics, which we might actually think of as
meaning "empiricists", in the sense of placing experience
and experiment at the center of knowledge-gathering practices. But we
should also see this in terms of language, remembering the link
between Montaigne and his project of representing natural experience
through his new genre of the essay, and Bacon's own attachments
to empiricism, experimentalism, and the genre of the essay, along with
other forms of representational writing, including fictional
storytelling and the use of aphorisms alongside other more
recognizable philosophical genres.



Diderot's eclecticism and materialism nevertheless remain in
tension, since eclecticism is not conducive to foundational
ontological commitments, while materialism, whatever the specific
matter theory it bases itself on, seems to be a paramount case of a
foundationalist ontology. What is real is matter, or perhaps, what the
sciences of matter declare to be real (and this can vary widely, from
the chemistry of mixts which Diderot was so fascinated by
[Pepin 2012], to the nascent biology he seems to be calling for
in the *Pensees sur l'interpretation de la
nature*, as we discuss below, to physics). And yet, as a series of
propositional *pensees* offered to readers without any
interconnecting discursive bridge between themes, this text also
propounds eclecticism methodologically, in contrast to a
systematically presented set of premises, arguments and conclusions.
This play between imaginative possibility and demonstrative certainty,
and between what rationally must be and what language is capable of
capturing and conveying in human terms is characteristic of
Diderot's thought overall, and his philosophy cannot be shorn of
this conceptual linguistic instability without destroying its
power.



In the next three sections, we discuss his empiricism, his materialism
and what we term his philosophical anthropology, namely, his ideas
concerning features specific to human beings, such as aesthetics and
ethics, although as we discuss, these are also located within
Diderot's overall commitment to naturalism.


### 2.2 Radicalizing empiricism


#### 2.2.1 Empiricism, from epistemology to ontology



Diderot is heavily influenced by Locke and in general by a kind of
empiricism that was "in the air": our knowledge about the
world is derived, either fully or at least in large part, from our
senses. In the *Lettre sur les aveugles* and its companion
piece, the *Lettre sur les sourds et muets*, as well as later
pieces such as the *Reve*, Diderot turns the question of
the senses and how we know the external world on its head: the senses
possess or carry with them their own respective metaphysics. It is a
powerful kind of relativism. And there is a new hierarchy in which
touch is fundamental, in direct opposition to classical philosophical
doctrines in which sight received that honour: throughout his work,
but especially in these two essays devoted to the metaphysics of the
senses and his various aesthetic writings, Diderot insists on the
primacy of touch, which he also describes as "the most
philosophical of senses"; he deplores the fact that "the
hands are despised for their materialism" (*LSM*; DPV IV:
15, 54). This is even given atheist overtones in the *Lettre sur
les aveugles* when the blind mathematician Saunderson on his
deathbed declares that "if you wish me to believe in God, you
will have to make me touch him" (DPV IV: 48).



Diderot expresses his materialism in this work through the character
of a blind man, also because he is like a living counterexample to the
argument from design. Indeed, Saunderson says to his interlocutor, who
is defending physico-theological design and order: "What did we
do to God, you and I, so that one of us possesses this organ (of
sight), and the other of us is deprived of it?" (DPV IV: 63). In
a further twist, Diderot also equates the blind man with idealist
metaphysics since it is also cut off from direct sensory engagement
with the world. Here, empiricism is no longer just a doctrine about
the sources of knowledge, i.e., an epistemology. The world of a blind
man is different from that of a deaf man, and so forth. Further, an
individual who possessed a sense in addition to our five senses would
find our ethical horizon quite imperfect (DPV IV: 27).



A similar displacement of the "scope" of empiricism occurs
in the companion *Lettre sur les sourds et muets*, with a
rather different version of Condillac's thought experiment of
the statue:



> 
> 
> My idea would be to decompose a man, so to speak, and examine what he
> derives from each of the senses he possesses. I recall how I was once
> concerned with this sort of metaphysical anatomy, and had found that
> of all the senses, the eye was the most superficial, the ear the most
> proud, smell the most pleasurable, and taste the deepest, most
> philosophical sense. It would be a pleasant society, I think--one
> composed of five people, each of whom only possessed one sense. They
> would undoubtedly call each other mad, and I leave you to imagine how
> right they might be. Yet this is an image for what happens to
> everyone: one only has one sense and one judges on everything. (DPV
> IV: 140)
> 
> 
> 



The senses here are treated as producing "worlds" in which
we live, not as epistemological sources of knowledge, which was the
strict issue raised by
 Molyneux's Problem
 (if a person born blind, with an understanding of basic mathematics,
recovered their sight and saw a cube, would they instantly know what
it was?), a problem that goes through considerable reconfiguration
with the character of Saunderson.


#### 2.2.2 Empiricism and experimentalism



Empiricism is further transformed by Diderot in accordance with his
project to transform knowledge by inscribing it in the sphere of
practice and "arts and crafts", especially with the
*Encyclopedie*. He sometimes refers approvingly to the
manual labourer (*manouvrier*)'s production of an
artisanal knowledge, notably in his 1753 *Pensees sur
l'interpretation de la nature* (SS XXX), which
not coincidentally sounds Baconian and Lockean. But more surprisingly,
he also equates this transformed, even "enhanced" vision
of empiricism with a metaphysics. That is, on the one hand he is an
empiricist advocating the experimental sources of new knowledge,
sometimes presented as "experimental philosophy":



> 
> 
> Experimental philosophy does not know what its work will yield or fail
> to yield; but it works without pause. On the contrary, rational
> philosophy weighs the possibilities, makes pronouncements, and stops
> there. It boldly declares, *light cannot be decomposed*;
> experimental philosophy listens, and remains silent for centuries;
> then suddenly shows us the prism, and declares, *light is
> decomposed*. (*IN*, SS XXIII; DPV IX: 43-44; his
> emphasis)
> 
> 
> 



We can also see this anti-foundationalist and experimentalist attitude
as challenging Descartes' "chains of reasons" which
extend to all our knowledge of things; Diderot begins the above work
by explaining that he will let his thoughts follow the order in which
objects presented themselves to his reflection (SS I). Such a view
is also resonant with what we might term Malebranche's
quasi-sensationalism, which locates scientific thinking in the
reduction of our stream of sensate observations to the rationalizing
logics of mathematical analysis, if we consider that, aside from the
"occasionalism" which has dominated his Anglophone
reception, much of Malebranche's *Recherche de la
verite* is about how our bodily passions and our sensations
produce errors in us, which makes Malebranche a sensationalist in
recognizing that conception of the human subject as the start for any
epistemological project of knowing. Diderot, from the *Lettre sur
les aveugles* on, is a dedicated empiricist and sensationalist,
although he expands the remit of these philosophical programs far
beyond "epistemology".



But on the other hand, Diderot treats the idea of experimental
philosophy rather playfully, both endorsing it and going beyond it in
a more speculative direction, as when he mockingly refers to the
mathematician's self-confident rejection of metaphysics by
writing, "the metaphysician ... is someone who knows
nothing", and comments that



> 
> 
> chemists, physicians, naturalists and all of those engaged in
> experimental practices (*l'art experimental*)
> ... seem to me to be on the point of avenging metaphysics, and
> applying the same definition to the mathematician (*IN*, SS
> III; DPV IX: 29-30)
> 
> 
> 



avenging metaphysics, in the sense of turning the charge of being
overly speculative back at the scientists!


#### 2.2.3 An experimental metaphysics



Sometimes the empiricist and the metaphysical tendencies are
encapsulated in a single formulation, as in the "experimental
metaphysics" in the *Bijoux indiscrets*, by which he
means an experience-based metaphysics, building up from the fact that
"all is experimental in us" (*SA*; DPV XVI: 87);
this formulation does not mean that we are the result of an endless
series of trial and error attempts, but that all results from
experience.



In his *Encyclopedie* article
"Metaphysique", Diderot also opposes an abstract
metaphysics of time, space and being to a practice-based metaphysics:
he suggests that practitioners such as musicians and geometricians be
asked about the "metaphysics of their art", which will
yield promising results, just as in the *Pensees sur
l'interpretation de la nature* he lauded the figure
he described as the "manouvrier
d'experience", a kind of artisan-experimenter whose
practice has yielded, over years of experience, an artisanal
knowledge.



Contrary to a now-common idea that the opposition between rationalism
and empiricism should be replaced with a more historically legitimate
opposition between experimental philosophy and speculative philosophy
(Anstey 2005), Diderot's case suggests a blend between
empiricism *cum* experimentalism, and speculation. He is often
confronted with the need to continue his analysis of phenomena beyond
the limits of strict empiricism: the nature of matter, the limits of
animation or on the more internal scale, the functioning of the
nervous system or the mechanics of generation. And here the need for
metaphysical imagination comes into play, which is not the same as a
strictly abstract metaphysics. Once again, Diderot's criticisms
of mathematical abstraction in favor of the greater concreteness of
the life sciences, which he shares with Buffon, can be adduced
here.


### 2.3 Materialism, science and living matter



Diderot was not a physician like La Mettrie, or a "working
natural historian" like Buffon, although at one point he wrote
that, "It is very hard to do metaphysics or ethics well, without
being an anatomist, a naturalist, a physiologist, and a
physician" (*RH*; DPV XXIV: 555). Nevertheless, one of
his first publications was the translation of James'
*Medicinal Dictionary* (1745), and in addition to his enormous
activity as the chief editor of the *Encyclopedie*,
which heavily features medical entries, sometimes with his editorial
interventions, he was also a serious student of chemistry, including
"vital chemistry" (Pepin 2012). Later in life he
declared that "there were no books I read more willingly than
medical books" (*EP*; DPV XVII: 510).



Given this background, Diderot's interactions with the life
sciences of his time can be understood, obviously, as the activity of
an educated individual with a strong interest in the implications for
philosophy of new scientific discoveries and conceptual schemas,
whether from medicine, biology, or natural history. But his
articulation of all of these in a *materialist project* does
not belong to or open onto an episode amongst others in the history of
science. That is, his articulation of a unique kind of philosophical
materialism is indeed in "dialogue with" or
"influenced by" the sciences of his time, particularly the
life sciences (which included chemistry for Diderot), but it is also a
speculative project; materialism in Diderot's time, like in
ours, was not a monolithic concept (Springborg and Wunderlich [eds]
2016).


#### 2.3.1 Vital materialism as "modern Spinozism"



Diderot opposed the novelty and conceptual significance of the life
sciences to what he (incorrectly) judged to be the historical
stagnation of mathematics:



> 
> 
> We are on the verge of a great revolution in the sciences. Given the
> taste people seem to have for morals, *belles-lettres*, the
> history of nature and experimental physics, I dare say that before a
> hundred years, there will not be more than three great geometricians
> remaining in Europe. The science will stop short where the Bernoullis,
> the Eulers, the Maupertuis, the Clairauts, the Fontaines and the
> D'Alemberts will have left it.... We will not go beyond.
> (*IN*, SS IV; DPV IX: 30-31)
> 
> 
> 



Similarly, in a letter to Voltaire five years later (February 19
1758), he wrote clearly that "The reign of mathematics has
ended. Tastes have changed, in favor of natural history and
letters". Diderot is opposing the new "taste" and
interest for a set of preoccupations including two forms of
"life science" (natural history and "experimental
physics") to the traditional prestige of mathematical science.
In these passages, he is also squarely locating his materialist
preoccupations within the former.



Diderot's natural philosophy is deeply and centrally
"biologistic". As it emerges in the mid-eighteenth
century, at a time before the appearance of the term
"biology" as a way of designating a unified science of
life, his project is motivated by the desire both to understand the
laws governing organic beings and to emphasize, more philosophically,
the uniqueness of organic beings within the physical world as a whole.
Consider a little-known aspect of Diderot's articulation of his
project: his statement in favour of biological epigenesis within his
short entry "Spinosiste" in the
*Encyclopedie*. The entry does not bear his name, but
large parts of the content occur elsewhere in his writings, and it is
included in all editions of his works. Here he grafts new biological
ideas such as epigenesis onto a Spinozist substance metaphysics (Wolfe
2014a), distinguishing between "ancient" and
"modern" Spinozists and emphasizing that the latter
specifically hold that "matter is sensitive", as
demonstrated "by the development of the egg, an inert body which
by means of heat alone moves to the state of a sensing, living
being". For modern Spinozists, "only matter exists, and
that it is sufficient to explain everything. For the rest, they follow
ancient Spinozism in all of its consequences" (*Enc.* XV:
474).



Diderot is rather unexpectedly combining Spinoza's metaphysics
of substance with a new theory of biological development, epigenesis,
according to which the embryo grows by the successive addition of
layers of purely material substance. Why call the latter view
"modern Spinozism"? The "ancient Spinozists"
are substance monists and metaphysicians, while their modern
descendants are also committed to biological epigenesis, and assert
that matter is fundamentally *living* matter. Is this Spinozism
or not? What possible relation could there be between Spinozism and
epigenesis? Or how can a metaphysics of substance and modes, which
says almost nothing about biological entities even if it is also a
major statement of philosophical naturalism, also be a fashionable
embryological theory of the seventeenth and eighteenth centuries? In
fact, very few commentators have asked *why* Diderot gives such
an idiosyncratic definition of "modern Spinozism".



To be sure, his convictions regarding living matter (or all of matter
inasmuch as it is potentially living and sensing) are tied to his
admiration for the metaphysics of a single substance composed of an
infinite number of modes. As he states in the *Reve de
D'Alembert*, "There is only one substance in the
universe" (DPV XVII, 107; Wartofsky 1952/1979, Deprun 1986,
Bourdin 2008). But nowhere does Spinoza seek to connect his
metaphysics to the life sciences; even if the notion of the conatus
was frequently taken up in the generations after him to mean something
like a survival impulse in living beings, this was not what he meant
at all. Diderot is grafting "vitalist" elements onto a
substance metaphysics, or at least, he is connecting an apparently
empirical account of the *self-organisation* of matter with a
new metaphysics. Epigenesis is not just one biological theory among
others here, but rather, part of a revised metaphysics of matter,
which Diderot presents in more overtly ideological terms in the
*Reve*:



> 
> 
> Do you see this egg? With this you can overthrow all the schools of
> theology, all the churches of the world. What is this egg? An
> unsensing mass, prior to the introduction of the seed
> [*germe*]; and after the seed has been introduced, what is it
> then? Still an unsensing mass, for the seed itself is merely an inert,
> crude fluid. How will this mass develop into a different [level of]
> organisation, to sensitivity and life? By means of heat. And what will
> produce the heat? Motion. (DPV XVII, 103-104)
> 
> 
> 



Matter for Diderot is self-organizing and endowed with vital
properties. This implies that his brand of materialism is not
synonymous with
 physicalism
 (admittedly, not a term or notion of the period). There were of
course materialists such as
 Hobbes
 who can also be described as physicalists, but Diderot was quite
explicitly a determinist, as we will discuss below (in
 section 2.4).
 This leads to two rather original consequences, which we examine in
the following sections: Diderot's metaphysics of vital matter is
not strictly experimentally based, it is also speculative; and his is
a specifically *embodied* materialism.


#### 2.3.2 Matter theory and living matter



In the very first paragraph of *Le Reve de
D'Alembert*, the character D'Alembert, who is a
partisan of substance dualism and is challenging the character
Diderot--a materialist--to account for the existence of
consciousness and thought, introduces the problem of sensibility
(*sensibilite*, better translated
"sensitivity") as a property. Referring to a discussion
that seems to have occurred before the text begins, he declares to
Diderot, "this sensitivity ... if it is a general and
essential quality of matter, then stones must sense" (DPV XVII,
90). Diderot states, revises, emends and restates this materialism of
living, sensing matter in a variety of works, both in the
*Reve* and in his more "empirically" oriented
writings such as the *Principes philosophiques sur la
matiere et le mouvement* and the *Elements de
physiologie*.



Later, building on an explicitly chemical matter theory, Diderot will
describe nature as perpetually "in action and reaction;
everything being destroyed in one form and recomposed in another;
sublimations, dissolutions and combinations of all kinds", in
the "general movement or rather fermentation of the
universe" (*PPMM*; DPV XVII: 17-18). This short
piece of "philosophy of physics" includes a polemic aimed
at all those who define matter as inert and homogeneous (latter-day
Cartesians). Diderot wants to establish in contrast that motion is
inherent in matter by joining together translation and *nisus*.
Indeed, matter possesses properties including sensitivity.



The key property of living matter, and of all matter potentially, is
organic sensitivity. Diderot often suggests that "sensitivity or
touch is common to all beings", and he often attributes
sensitivity to matter as a whole (*EP*; DPV XVII: 308). In
"Leibnizianisme", he brings together Aristotle's
entelechy, Leibniz's monads, and sensitivity as a "general
property of matter" (*Enc.* IX: 371); indeed, Leibnizian
metaphysics and theories of generation had a great impact on
eighteenth-century thought, and has been viewed as major influences in
the formulation of Diderot's materialism, albeit in naturalized
form, e.g: "the monad, the real atom of nature, the true element
of things" (*Enc.* IX: 374a). Elsewhere, such as the 1765
Letter to Duclos, Diderot denies that sensitivity can be a property of
a molecule, specifically because it can only be a property of matter
itself. He then complicates the issue further by introducing a
distinction between "inert" sensitivity and
"active" sensitivity.



Nevertheless, Diderot's matter theory is very much one of a
living, sensing, self-transforming matter, sometimes specified in
chemical terms:



> 
> 
> You can practice geometry and metaphysics as much as you like; but I,
> who am a physicist and a chemist, who take bodies in nature and not in
> my mind, I see them as existing, various, bearing properties and
> actions, as agitated in the universe as they are in the laboratory
> where if a spark is in the proximity of three combined molecules of
> saltpeter, carbon and sulfur, a necessary explosion will ensue.
> (*PPMM*; DPV XVII: 34)
> 
> 
> 



The critique of mathematical abstraction in favor of a more
empirically rich matter theory, whether this is presented as deriving
from natural history, chemistry, medicine, physiology or other
disciplines, is also a constant in Diderot. The point we would
emphasize most, however, is that this is also a *speculative
metaphysics*. The shift from inert to active sensitivity is not
experimentally grounded. That Diderot's materialism was not
strictly an outgrowth of empiricism, and/or experimentally based, as
one might expect given the usually close relation between scientific
practice and materialist philosophy, is also apparent in the
dimensions he sometimes is willing to allow to his cosmogony of
universally living matter.



On one occasion, he wrote to Sophie Volland describing how such ideas
led him to be teased, but he pushes them even further in the letter,
in the direction of a materialist account of love. The result is not
so much a reductionist explanation of the phenomenon of love as a
romanticization of materialism itself:



> 
> 
> The rest of the evening was spent teasing me about my paradox. People
> gave me beautiful pears that were alive, grapes that could think. And
> I said: Those who loved each other during their lives and arrange to
> be buried next to one another are maybe not as mad as one thinks.
> Their ashes may be pressed together, mingling, uniting. What do I
> know? Maybe they have not lost all feeling, all memory of their prior
> state. Maybe they have a remainder of heat and life, which they enjoy
> in their own fashion, at the bottom of the cold urn in which they
> rest. We judge the life of elements by the life of crude aggregates.
> Maybe they are entirely different entities.... When the polyp is
> divided into a hundred thousand parts, the primitive, generational
> animal is no longer, but all of its principles are still alive. O my
> Sophie, I then still have a hope of touching, sensing, loving, seeking
> you, uniting and melding with you, when we are no longer. If there
> were a law of affinity amidst our principles, if we were entitled to
> compose a common being; if, in following centuries, I were to comprise
> a whole again with you; if the molecules of your dissolved lover were
> to stir, to move about, and search out yours, scattered throughout
> nature! Grant me this chimaera. It is sweet to me. It would ensure my
> eternity in you and with you .... (letter of 15 October 1759,
> translation C. Wolfe)
> 
> 
> 



This image of a kind of eternity in which "loving
molecules" gradually return to one another, impelled by a
residual consciousness of the love present in their "parent
bodies", resonates with the powerful rendition he gives in the
first dialogue of the *Reve* of the thought experiment of
the statue. Recall that the character D'Alembert had challenged
the character Diderot to show that matter could think, and the latter
had retorted that if he could show that matter could sense the
solution would be found. The character Diderot then proposed a thought
experiment of a marble statue, ground into powder, mixed into the
earth, out of which plants grow that are eaten by animals who are in
turn eaten by us. He calls this process the
"animalization" of matter. Thus framed, the difference
between a piece of marble and a sensing, conscious creature is only a
difference in the temporal stages of a portion of matter in
transformation. Unlike Condillac's statue, Diderot's is no
longer a strictly epistemological account of the genesis of our
knowledge (and self-consciousness) through the accumulation of
intermodal sensory information. Instead, it is an assertion of the
animalization of inert matter, such that all matter is either actually
or potentially alive.


#### 2.3.3 Body and embodiment



But what of actual bodies in this universe of living matter?
Diderot's notion of body is quite different from, say, that of
Descartes and Hobbes. "As a physicist", Diderot writes,
"one should never say *the body qua body*, because this
is no longer physics, it is making abstractions which lead to
nothing" (*PPMM*; DPV XVII: 16). As he wrote to Sophie
Volland, "Have you ever thought seriously about what it is to
live? ... Life is not just motion, it is something else"
(letter of 15 October 1759). Indeed, he may quite fairly be described
as a theorist of embodiment.



His materialist notion of embodiment means that Diderot does not
oppose the living body as a kind of subjectivity to the world of
matter overall. As is particularly apparent with Saunderson in the
*Lettre sur les aveugles* and the account of the nervous system
in the *Reve de D'Alembert*, Diderot "pit[s]
the unity of sensibility against a Cartesian unity of
subjectivity" (Gaukroger 2010: 416). However, this emphasis on
embodiment is neither a "top-down", emergent view of life
(even if "life is not just motion"), nor an
antireductionist position (contrast Kaitaro 1997). For Diderot,
emphasis on the features of the living body and a deflationary and/or
reductionist attitude go hand in hand. "The action of the soul
on the body is the action of one part of the body on another",
he writes, "and the action of the body on the soul is again that
of one part of the body on another" (*EP*; DPV XVII:
334-335). This was certainly reductionist in the eyes of
defenders of an immortal and/or immaterial soul, but it is not per se
*eliminativist* inasmuch as Diderot is saying that
"mental processes" (if we take the language of
"soul" here to be psychological language) are bodily
processes, not that they are illusory or otherwise unreal. Similarly,
commenting on the Dutch scientist Franz Hemsterhuis' manuscript,
he notes: "wherever I read *soul* I replace it with
*man* or *animal*" (DPV XXIV: 340). This is a
venerable trait of materialisms going back at least as far as
Lucretius, and Diderot does not necessarily deploy this tradition to
deny the existence of the soul, but rather to challenge the
"animist" or the "idealist" claim "to
explain anything without the body" (*EP*; DPV XVII: 334).
Even more interestingly, this shift can also be seen in broader terms
as a shift within *reductionist* strategies, which we can also
classify as *types of reduction*.



One strategy for the early modern materialist was to deny the
existence of a "higher-level" entity such as the soul (or
free will, or thinking, etc.) in favor of a hypothetical "basic
physics" or the properties of matter in general. Thus La Mettrie
wrote, in his 1748 *L'Homme-Machine*, that



> 
> 
> The soul is just a pointless term of which we have no idea and which a
> good mind should only use to refer to that part of us which thinks.
> Given the slightest principle of movement, animate bodies will have
> everything they need to move, feel, think, repent and in a word,
> behave in the physical realm as well as the moral realm which depends
> on it. (La Mettrie 1987, vol. I: 98)
> 
> 
> 



In contrast, another strategy is to construe "soul" in
functional terms, as not conflicting in any way with a basic
materialist ontology, if it is not a substance of its own. Thus the
materialist could be less overtly confrontational towards the concept
of soul. For instance, because it has been naturalised, the soul can
be treated, as La Mettrie suggests, as "but a principle of
motion or a material and sensible part of the brain" (La Mettrie
1987, vol. I: 105). Here, as in Diderot, the status of the soul is
displaced away from metaphysics towards the particular physiological
site of the brain. Diderot's *Elements de
physiologie*, as well as his supplementary remarks in the article
"Ame", stress both the complexity of the brain for
any reductionist materialist project, and the
"displacement" of the soul therein. The concept of the
body which is at work in these materialist texts is, if not
"ensouled", certainly animated and vitalised, as in this
remark of Diderot's:



> 
> 
> Whatever idea we initially have of [the soul], it is necessarily a
> mobile, extended, sensitive and composite entity. It grows tired just
> like the body, it rests like the body, it loses its control over the
> body just as the body loses its control over the soul.... Is the
> soul gay, sad, angry, tender, shy, lustful? It is nothing without the
> body. (*EP*; DPV XVII: 334)
> 
> 
> 



He also presents the brain as the source of our identity, or of what
it is for me to be me, although he sometimes thinks it is the whole
organism which composes our individuality. He recognizes the brain as
a very particular kind of organ, one in need of special attention,
and, rather unusually for the period, he seems to call attention to
its plasticity in a discussion of memory:



> 
> 
> The soft substance of the brain [is] a mass of sensitive and living
> wax, which can take on all sorts of shapes, losing none of those it
> received, and ceaselessly receiving new ones which it retains. There
> is the book. But where is the reader? The reader is the book itself.
> For it is a sensing, living, speaking book, which communicates by
> means of sounds and gestures the order of its sensations. (DPV XVII:
> 470)
> 
> 
> 



Diderot had been discussing several extremely lyrical cases of
recalling landscapes both in nature and in painting, and then almost
abruptly turns to cerebral-material explanations of such phenomena.
What is unusual about this in the history of philosophical and early
neurophysiological discussions of the brain is Diderot's
striking image of the brain as a book which reads itself, and the
embodied brain-reader as self-organizing (Wolfe 2016b).



Even if Diderot's conception of body and brain indicate that he
is not treating them in terms of basic physics alone, he holds the
existence of causal relations to be fundamental; as he writes,
"'Every cause is an effect' seems axiomatic to
me" (DPV XXIV: 309). Without this foundationally construed sense
of causality, Nature would constantly be taking leaps, which he thinks
is a mistaken vision of things. In other words, he is committed to a
form of determinism.


### 2.4 Determinism and change



All forms of materialism are deterministic, but in different ways.
Nothing compels the materialist to accept that the body and the
passions are deterministic *just like* a simple machine.
Unsurprisingly, a lot depends on how *causes* are understood,
and how much weight they are meant to bear in both an ontology and an
account of action (see entry on
 causal determinism).
 Thus it is quite possible to hold, like Helvetius,
d'Holbach or Hobbes, that there is a fixed, stable and
predictable relation between our sensory input, our mental life and
consequently our "temper" and our actions. "As a
being that is organized so as to think and to feel",
D'Holbach explained, "you must feel pleasure or pain; you
must love or hate in accordance with the way your organs are affected
by the causes surrounding you or within you" (D'Holbach
1770/1781: I.i [1990: 18]).



But the organismic elements in Diderot's materialism and vision
of the body lead him to challenge Helvetius' program of
reform, which asserts, on the basis of an empiricist and specifically
sensationalist epistemology, that human beings really are *fully
modifiable* "blank slates", modifiable in terms of
what we call stimuli and responses. Interestingly, it is by denying
this "full modifiability" that Diderot can defend a
certain notion of individuality. The fact that individuals differ from
each other at the level of their *organisation* grants them a
degree of self-determination. "Every day, I see men who prefer
to die rather than to correct themselves" (DPV XVIII: 344). That
is, what Diderot calls "modifiability", which might better
be termed "corrigibility", has limits, and these limits do
not just reflect some kind of blunt innatism (whether of genetic
heritage or of character), but rather a degree of individuality,
including at the level of agency. Biologically, Diderot often stressed
the enormous variation of traits such as intelligence from one
individual to another, noting that the difference between an
"idiot" and a "genius" hinges on tiny shifts
in "brain fibers". There is more difference, he insists,
between one individual and another in terms of intelligence than
between a human being and an animal (DPV XXIV: 299). But there is no
sharp divide between the biological and the personal, for Diderot.



Helvetius had described to Diderot how severely he was punished
for *De l'Esprit*, with the consequence that he would
"rather die than write another line again". Diderot
responds with a long tale about two cats he saw from his window, who
fell from a roof. One died from the fall, but the other got up,
bruised and bloodied, and said to himself,



> 
> 
> I would rather die than ever climb on the roof again. What am I
> looking for up there? A mouse that is not worth the tasty morsel I
> could get from my mistress, or steal from the cook ...
> 
> 
> 



However, as soon as the cat feels better, he climbs back up on the
roof again (*RH*; DPV XXIV: 542-543). Just like the cat
is determined by his own constitution and drives, similarly,
Helvetius has no choice but to go on writing.



Diderot's determinism is also his way of extending core
empiricist tenets such as *nihil est in intellectu quod non fuerit
in sensu* (there is nothing in the mind that was not first in our
sense), which acquires a determinist dimension: "there is only
one operation in man, sensing. This operation is ... never
free" (*OH*; DPV XXIV: 300; cf. *PC*; DPV XX: 85)
and



> 
> 
> perception comes from sensation; from perception, we get reflection,
> meditation and judgment. There is nothing free in intellectual
> operations, or in sensation. (*EP*; DPV XVII: 335)
> 
> 
> 



There is also a tension in Diderot's approach to determinism
between his acceptance of physicalism ("there is only one kind
of cause ... physical causes": to Landois, DPV IX: 258) and
causal closure ("the physical world and the moral world are one
and the same": *PC*; DPV XX: 53), and his insistence that
agency, which for him covers the action of complex organisms overall
and is not restricted to humans or even higher mammals, requires
another, specific kind of causality: "I am a man, and I require
causes proper to man" (*RH*; DPV XXIV: 523). Diderot is
not defending free will or an unchallenged space of agency, yet there
is a kind of residual anthropocentrism in some of his arguments,
presented in the language of unified causality. As he explains:



> 
> 
> Without regard for the sum of elements of which I am composed, I am
> one, and a cause only has one effect. I have always been one single
> cause [*une cause une*], thus I have never had more than one
> effect to produce; my duration is thus nothing more than a succession
> of necessary effects.
> 
> 
> 



Diderot is neither asserting total interconnection (as in Laplacian
determinism) nor defending the existence of freedom to act as
"indifference" or "agent causation", but an
intermediate view (once known as the Hume-Mill thesis) according to
which what it is to be "me" is to be a particular causal
nexus.In that sense, I cannot "do otherwise than myself"
or "be anyone other than myself" (*JLF*; DPV XXIII:
190, 28; on Diderot on individuality and selfhood, see Thiel 2015,
Wolfe 2015).



However, in good Lucretian fashion, this unified causal loop we call
"ourself" or "myself" is itself subject to
what Diderot terms "vicissitude", a term that connotes
change and flux in this context.



> 
> 
> In one and the same man, everything is in perpetual
> vicissitude... It is only by means of memory that we are the same
> individual to others and to ourselves. At my age, there may not be a
> single molecule in my body that I brought into the world at my birth;
> (*DPD*; DPV X: 423)
> 
> 
> 
> everything changes, everything passes ... only the Whole remains.
> (*RA*; DPV XVII: 128)
> 
> 
> 



Diderot wrote that



> 
> 
> fruits, vegetables and animals are in perpetual vicissitude as regards
> their qualities, forms and constituents; an ancient from four thousand
> years ago or better, our nephews in ten thousand years will most
> likely recognize none of the fruits we have today;
> 
> 
> 



thus



> 
> 
> we must be extremely careful in our judgments of the ancient
> historians and naturalists regarding the forms, virtues and other
> qualities of beings which are in perpetual alteration.
> ("Acmella", *Enc.* I: 460a)
> 
> 
> 



The instability in this continual movement between seemingly free and
willful individuality and collective, biological/metaphysical
determinism also sits at the heart of the perpetual dialectic between
"Moi"and "Lui" in *Le Neveu de
Rameau*.



Further, this emphasis on mutability, change and
"vicissitudes" including at a specifically biological
level can sound evolutionary to a post-Darwinian reader, and for
Diderot, "to be born, to live, to die is merely to change
forms" (*RA*; DPV XVII: 139), in the
"ever-changing" "overall order of nature":
"Everything is in *in fluxu et eterno et perpetuo et
necessario*" (*OH*; DPV XXIV: 317). He also
explicitly uses the Lucretian phrase *Rerum novus nascitur
ordo*. Should these passages be understood as anticipations of
evolutionary science? In fact, contrary to a widespread tendency in
older scholarship, it is mistaken to consider Diderot as either a
predecessor or a speculative exponent of evolutionary doctrines. That
he was an earnest disciple of Lucretius, fascinated with monsters and
with the transience and mutability of the physical (particularly the
living) universe overall, does not make him a "forerunner of
Darwin".



On the biological side, his fascination with monsters also feeds into
his philosophy of nature overall. "On the entire surface of the
earth", he writes,



> 
> 
> there is not a single man who is normally constituted or perfectly
> healthy. The human species is just a mass of more or less counterfeit,
> more or less sick individuals ... What I say of man applies just
> as well to animals, plants or minerals. (*EP*; DPV XVII:
> 515)
> 
> 
> 



This explains why, as he had written earlier,



> 
> 
> the dissection of a monster ... is more useful to the historian
> of nature [i.e., the experimental life scientist or biologist in
> modern parlance] than the study of one hundred individuals who
> resemble each other. ("Encyclopedie"; DPV VII:
> 242)
> 
> 
> 


### 2.5 Diderot's philosophical anthropology


#### 2.5.1 Aesthetics



Diderot was a thoroughgoing naturalist and empirical scientist, but
this did not mean that he neglected the aesthetic dimension of human
knowing, or the artifice of representation itself that makes possible
language, communication, and human knowledge. In his
*Encyclopedie* entry on cabinets of natural history and
their philosophical implications ("Cabinets d'histoire
naturelle"), he reflects explicitly on the challenge for our
finite intellects to seek to know infinite Nature as a whole, and
recommends the construction of artificial environments such as these
cabinets in order to study "parts of Nature". At times,
his vision of aesthetics is simply a kind of extension of his
naturalism into other domains, arguing like Spinoza that our
subjective notions of beauty and ugliness have no place in nature
properly understood (in the article "Laideur"; also
*Salon de 1763*; DPV XIII: 373-374), and argues for a
naturalist poetics ("Encyclopedie"; DPV VII: 234).
Yet he also held that aesthetics should not be reduced to crudely
naturalistic concepts, reflecting at length on the subjective issues
of aesthetic perception and judgment and the role of performance,
including that found in visual art, literature, theater, and
scientific experiments, in the production of perceived truths.



With respect to the ostensibly subjective side of human knowing, he
invested considerable energy in articulating a concept of
"perception of relations" (*perception des
rapports*) which functions both as a theory of judgment
(explaining why it is that we find certain kinds of symmetry and
proportion pleasing) and a theory of cognitive functioning at a more
basic level, one characterized by psychoneural relations, as it were.
Countering that subjective emphasis, however, Diderot also warned
against the "surfeit" of organic sensitivity as a source
of hyper-reactivity, and of sensory stimulus as a ground for
perception without any internal unifying principle. These reflections
are also found in the character Bordeu in the *Reve* who
serves to ground the perceptions and queries from Mlle de
Lespinasse regarding the ravings of the dreaming D'Alembert in a
clear objective ground. Diderot describes the overly sensitive actor
in the *Paradoxe sur le comedien* as suffering from a
"weakness in their constitution", and speaks ironically
about the welter of emotions ("des sensibilites
diverses") on stage being incapable of forming a unified
whole.


#### 2.5.2 Philosophy of language and representation



Unifying these two aspects was the eclectic Malebranchian emphasis
upon language as the bridge between the finite and the infinite, the
material and immaterial, the human knower and nature as a whole. In
his aesthetics, Diderot is continually preoccupied with the power of
art to capture and represent natural experience and its limitation in
the face of the infinitude, and often unrepresentable complexity, of
life. In meta-works of what might be called his philosophy of theater
such as *Discours de la poesie dramatique* and
*Paradoxe sur le comedien*, and in his dialogue where he
conversed out loud with his readers about the theatrical logic
underlying his play *Le Fils naturel*, Diderot also pursued
such themes by subjecting the "reality effect" of
theatrical art to a systematic interrogation so as to unearth the
rational structures of theater as a representative art form.



Diderot reflected famously and influentially on what he called the
"fourth wall of the theatre", that imaginary barrier that
separates an audience from the three dimensions of the stage it faces.
This is a barrier that for Diderot acts either as conscious division
dividing the actors and the drama from its viewer (theatre as a
consciously artificial way of representing and knowing) or as an
invisible screen through which the two join together into the joint
experience of the theatrical moment (theater as a staged naturalism).
While still important in theatre theory today--Richard Sennett
interprets Diderot as "the first great theorist of acting as a
secular activity" and as the innovator who creates a theory of
drama "divorced from ritual"--Diderot's
writings on theatre also offer yet another example of his wider
metaphysical and physiological understanding of human beings and their
embodied interrelation. They also highlight the role of language
throughout his philosophy as a tangible yet permeable and sometimes
fragile tether joining humans and their knowing together.



In a manner similar to his "philosophy of theatre",
Diderot's art criticism is also very often a study of the
continually recurring interplay between sensible human subjectivity
and the natural world through the perceived empirical reality of
natural representation. What happens when a viewer stands in front of
a painting and experiences its imagery? In particular, what is the
relationship between the reality of the viewer in the Louvre in the
salon gallery in front of the paintings on display and the reality of
the world represented by the image? What is it that happens exactly as
we move between these two worlds and realities? And given the presence
of both a painting and its artist at the center of this exchange, what
is the role played by the painter, his material medium, his craft in
manipulating matter into representations, and the viewing subject who
both receives this artistic work in her own senses and then recreates
it in her imagination in the making of a "natural
experience"?



To combine all these dimensions into a coherent concept of art, as
Diderot did in his art criticism, was to produce a general aesthetics
exploring the capacity for human representations to render experience
truthful and meaningful. Here, Diderot also explored the power and
limitations of such practices as a form of human experience. In this
way, the problem of viewing art and speaking about the experience of
viewing art, or the question of judging artists that stage this
experience, is akin to the problem of viewing and speaking about
nature itself, and of judging the nature of the presentations put
before us. Diderot's "promenade Vernet" in the
*Salon de 1767* is something of a locus classicus for these
investigations with its extended reflection on the presence of the
viewer in front of a Vernet landscape painting and the being of that
viewer in the natural world that the painting represents as well. His
work in natural philosophy and the life sciences often manifests a
similar subject-object preoccupation as well, and in this respect
Diderot's aesthetics and his natural philosophy have much in
common.



The same combination is present in Diderot's literary fiction as
well in his continual, and often critical, exploration of the
empirical reality of linguistic representation, and our capacities and
limitations for experiencing and knowing the world through such
representations. *Jacques le fataliste*, for example, is a kind
of anti-novel that thwarts the arrival of naturalized realism and
credible illusion at every turn even as it narrates a bawdy and
frolicking story. Characters break with the scenes and dialogue of the
story to talk directly to the reader, and the narrator himself is a
self-conscious character in the work who often finds himself in a
struggle with the fictions he is supposedly controlling and
representing for his readers.



*Le Reve de D'Alembert* is also concerned with the
relation between author, textual characters, and the naturalistic and
rational representation of thought in language and text, as is *Le
Neveu de Rameau*, but while these dialogues organize the play
between their various registers in a way that produces constructive
philosophical investigation, *Jacques le fataliste* operates
deconstructively, subverting the basic coherence of the novel as a
form by repeating paragraphs verbatim on multiple pages and by
intentionally distorting the book's narrative coherence and
flow. One entire page of the book is printed in complete black, for
example, to call attention to the print characters that make all
reading and linguistic communication possible. Diderot's story
*Ceci n'est pas un conte* also operates in this
subversive and deconstructive way by prefiguring Magritte's
famous conundrum regarding the image of a pipe through a
self-destructive recursion of a story that uses storytelling to deny
the possibility of storytelling even as it narrates a story.


#### 2.5.3 Ethics



One striking feature of Diderot's moral thought is his
self-described failure to write a work of moral philosophy. While
Diderot wanted to write such a work in order to refute La Mettrian
immoralism, especially its particularly bracing form of hedonism
coupled with its cynical social theory, he ultimately did not succeed
in this ambition. He interestingly described his failure, or rather
reluctance, to write a work of ethics as stemming from his recognition
that,



> 
> 
> if I do not emerge victorious from this attempt, I shall become the
> apologist of wickedness, I will have betrayed the cause of virtue, and
> encouraged man towards vice. (*RH*: DPV XXIV: 589)
> 
> 
> 



Diderot had no desire to use his writings to ensure "the
immortality of the evildoer" (*ibid*.; *ERCN* II,
6; DPV XXV: 246-247), and at the same time he also considered
normative moral philosophy to be a failure, a view he shared with such
virtuous individuals as Locke. (In response to his friend Lady
Peterborough's request for advice on how to morally educate her
son, Lord Morduant, Locke recommended, in a 1697 letter, that he
should read Livy (for history), along with geography and the study of
morality. But, he explained, "*I mean not the ethics of the
schools*", but rather Tully (i.e., Cicero), Pufendorf,
Aristotle and "above all the New Testament", wherein
"a man may learn how to live which is the business of ethics,
and not how to define and distinguish and dispute about the names of
virtue and vice" (King 1829: 5-6). This is not a ringing
endorsement of academic moral philosophy, and Locke reiterates this
view in his *Thoughts Concerning Education*, SS 185 and the
*Reasonableness of Christianity*, SSSS
241-242.)



Another crucial feature of Diderot's ethics was his dislike for
relativism or at least for some of its possible consequences. Diderot
learned a great deal from Locke, Montaigne and other paragons of early
Western cultural relativism. Montaigne and Locke paid close attention
to the case of cannibals; Locke, when he takes up the case of
cannibals in the *Essay*, uses it to support anti-innatist
views with respect to what he calls "practical principles"
(that is, moral principles of conduct): he points out that the
Tupinamba tribe in the Amazon considers that a high form of virtue is
eating one's enemies, along with many other examples of
"*enormities practised without remorse*", in order
to stress that "moral rules" are not innate but culturally
specific and learned (Locke 1690 [1975: I.iii.9]). The challenge is
not to morals per se but to "mores" and customs which we
take to encapsulate morality. Diderot echoes these ideas notably in
his *Supplement au voyage de Bougainville*, but contrary
to widespread views, he did not think that such relativism had to
entail libertinage, criticizing Hemsterhuis for reasoning "as if
libertinage was a necessary consequence of materialism, which seems to
me to match neither reason nor experience" (*OH*; DPV
XXIV: 251). Unlike La Mettrie (and the Marquis de Sade after him),
Diderot maintained a strongly social concept of self. "He who
has studied himself", he wrote, "will have advanced in the
knowledge of others, given, I think, that there is no virtue which is
foreign to the wicked, nor vice foreign to the good"
(*ERCN*; DPV XXV: 226).While he did not develop a full-fledged
theory of sympathy like Hume or Smith, Diderot was nevertheless
acutely conscious of the role of the passions in cementing the social
bond, and how this role should be promoted in any viable ethical
theory.



Nevertheless, his hostility to immoralist versions of materialism did
not mean that he reneged on his overall naturalism, since his account
of our behavior, and of good and evil, also seeks to tie it to our
physiological constitution (our *organisation*, in his
terms).



> 
> 
> Ethics is confined to the borders of a species ... What is a
> species? A mass of individuals sharing a similar constitution. What,
> is this constitution the basis of ethics?... I believe so.
> (*SA*; DPV XVI: 206)
> 
> 
> 



It is perhaps too naturalistic an ethics for some since "there
is no rational goodness or wickedness, although there may be animal
goodness or wickedness" ("Droit naturel",
*Enc.* V: 155b). By this Diderot means that we do not act in
accordance with purely transcendent or immaterial principles in mind,
but that we are determined by motives, affects, desires, instincts and
so on. Yet at the same time, as we also saw regarding determinism,
Diderot is concerned not only with the universe in its entirety but
with specifically human chains of causal influence as well.
"What is a human being?" he asks. "An animal?
Undoubtedly, but dogs are animals too; so are wolves. Yet humans are
neither wolves nor dogs" (*SA*; DPV XVI: 205).



Diderot explicitly eschews the natural ties that many see tying a
materialist conception of human being directly and naturally with
libertinism, hedonism, and a purely self-interested and solipsistic
conception of morality. This stance was reinforced in other ways by
his counter-conception of natural morality, an ethics which he often
celebrated in his writings about aesthetic representation and its
value. At the center of the naturalism that Diderot claimed for this
ethics was an implicit set of claims about experience, feeling, and
action in human life. The natural principles of sensibility spoke
directly to humans about the division between virtue and vice, or so
Diderot believed, and while the virtuous individual was the one who
submitted to the natural passions inherent in us pushing us toward
camaraderie and filial love, the vicious soul was a willful and
arrogant rebel who chases selfish desire and self-gratification
against the grain of what is naturally good and true.



This metaphysical and physiological understanding of morality was
central to Diderot's politics as well, and with respect to
theater it led him to theorize the mechanisms by which human
performance and theatrical display both supported and corrupted the
pursuit of virtue. Rousseau, with similar ethical orientations,
condemned theater outright as a false and corrupting medium, arguing
that natural religion and virtue could only be practiced in a natural,
i.e., non-artificial or non-theatrical way. Diderot's view was
much more complicated. While he recognized the corrupting power of
artistic representation to deceive, he also recognized its power to
provoke and sustain natural experiences that promoted moral virtue.
His impassioned speeches written for imagined Africans oppressed by
European slavery, which he included in his contributions to
Raynal's *Histoire des deux Indes*, illustrate well the
fusion of theater and politics characteristic of Diderot. In these
moments, Diderot used the full power of theatrical language and
artificial representation to present an unequivocal statement about
moral and political righteousness, one designed to move people to
progressive and virtuous political action. Rousseau's prize
essay discourses produced in the 1750s were also influential upon
Diderot in shaping his views, for like Rousseau Diderot developed an
ideal of natural, egalitarian, communitarian virtue, which he found
most fully developed in simple, rustic people who lived modestly and
in close relation to their natural surroundings. Diderot also
developed a countervailing conception of vice that was directly
connected to wealth, especially wealth attached to elite privilege,
and a morality that encouraged people to embrace basic organic
foundations for life and to turn away from urban lives of selfishness
and hedonism. The same morality infused his political economic
writings as well, both in his celebration of the communitarian power
of commerce to unite people into virtuous and prosperous polities, and
in his critique of greed and commercial excess as a cause for social
violence and political injustice.


#### 2.5.4 "Man and world"



At the level of aesthetics, ethics or ontology itself, Diderot is a
materialist concerned with utility, praxis, transformation and yes,
agency (up to a point). Some commentators in earlier generations
thought this spelled contradiction and the lack of any cogent
philosophical position. More recently, it has been recognized that
Diderot was precisely reflecting *on this tension* between the
cosmos and time-scales stretching millions of years, and his love for
Sophie Volland, or his desire to see goodness rewarded and wickedness
punished. Indeed, he sometimes offers at least partial solutions to
this old aporia. If it is true, on the one hand, that



> 
> 
> The universe only presents to us particular beings, infinite in
> number, with hardly any fixed or determinate division. None can be
> termed the first or the last; everything is linked therein, and
> follows what came before by imperceptible nuances. In this immense
> uniformity of objects, if some appear which, like the tips of rocks,
> seem to pierce through the surface and dominate it, they only owe this
> prerogative to particular systems, vague conventions, and foreign
> events, not to the physical arrangement of beings and the intention of
> Nature ("Encyclopedie", *Enc.* V: 641b)
> 
> 
> 



so that there is no place for the human observer in this desolate
landscape, it is also true, on the other hand, that the only thing
that makes the existence of the spectacle of Nature interesting is the
human presence itself:



> 
> 
> One consideration above all must not be lost sight of, and that is
> that if man or the thinking, contemplating being is banished from the
> surface of the earth, this moving and sublime spectacle of nature
> becomes nothing but a sad and mute scene.... Everything changes
> into a vast solitude where unobserved phenomena occur in a manner dark
> and mute. (*Enc.* V: 641c)
> 
> 
> 



Instead of losing himself in reveries about the poetics of ruins and
our transitory existence on the face of the earth, however, Diderot
instantly asserts the pragmatic, "constructivist" and
artificialist conclusion: since "It is the presence of man that
makes the existence of beings interesting", "Why not make
man the center of our work?" The anthropocentrism here is of
course not one which appeals to a human essence, or special dignity
including some purported superiority we might possess over animals. It
is rather a pragmatic position according to which schemes like the
*Encyclopedie*, but also the arts, sciences and
technological pursuits narrated in that work, serve to make that
"landscape" meaningful.


## 3. Conclusion



For Diderot, there is only one substance and it is material. Here, he
is loosely aligned with Spinoza. But this substance is in perpetual
flux (a more Lucretian element in his thought), so that the individual
beings we encounter are merely temporary, provisional clusters of
molecules in interaction with one another, in the midst of what he
terms the general "vicissitude" of the cosmos (by which he
means its change). In the entry "Immuable"
("Immutable") he writes that "Nature is in a state
of perpetual vicissitude. It follows from the general law of all
bodies: either they are in motion, or they tend to be in motion"
(*Enc.* VIII: 577).



Borrowing a Heraclitean motif and adding a now rather dated gender
inflection, Diderot also describes Nature as a woman who enjoys
disguises (*IN*, SS XII, doubtless alluding to
Heraclitus' *phusis kruptesthai philei*, "Nature
likes to hide", frag. 208). This is also why there are no
monsters in any real sense:



> 
> 
> I speak of monstrosity relative to what they are at present, for there
> are no monsters relative to the whole .... If everything is
> *in fluxu*, which we can hardly doubt, all beings are
> monstrous, that is, more or less incompatible with their corresponding
> order. (*OH*; DPV XXIV: 317, 403)
> 
> 
> 



The matter of which we, as well as all other entities in the universe,
are composed, is heterogeneous: differing in terms of energy and
sensitivity, and in perpetually evolving relation to the Whole:



> 
> 
> The world is ceaselessly beginning and ending; it is at every moment
> at the beginning and at the end; it never had, and never will have any
> other. In this vast ocean of matter, not one molecule resembles
> another, not one molecule is self-identical for one moment.
> (*RA*; DPV XVII: 128)
> 
> 
> 



That is, Nature is both fundamentally heterogeneous (the atoms which
compose the natural world exist in a state of heterogeneity and
agitation) and never entirely "specific":



> 
> 
> each thing is more or less specific (*quelconque*), more or
> less earth, more or less water, more or less air, more or less fire;
> more or less belonging to one kingdom or another ... hence there
> is no essence of a particular being. (*RA*; DPV XVII: 138)
> 
> 
> 



All beings



> 
> 
> have an infinite number of relations to one another, according to the
> qualities they have in common; ... it is a certain assemblage of
> qualities which characterizes them and distinguishes them
> (*BI*; DPV III: 183)
> 
> 
> 



In this ever-changing Whole, there are provisional constructs and
entities that are, like everything else, wholly material, but can be
of greater or lesser significance to us, whether this is "cashed
out" aesthetically, emotionally, ethico-politically or even in
terms of nerve impulses (and Diderot, most of the time, is not wont to
distinguish sharply between these).



Diderot invented a new form of materialism, drawing on a variety of
sources including the Epicurean tradition, Hobbes and Locke, Spinoza
and Leibniz. He also transformed doctrines, genres and nascent
intellectual constellations (skepticism, the philosophical novel, and
eclecticism, to name some instances). Even if he did not wish to
contribute to the genre of systematic philosophy, his contribution to
the Enlightenment (and its posterity) and to subsequent intellectual
episodes is considerable, difficult to measure, and should be engaged
with.