The French Enlightenment I: science, materialism and determinismPeter JimackThe French Enlightenment is not just a convenient label devised by historians ofphilosophy, and the thinkers to be discussed in this chapter and the next were for the mostpart conscious of belonging to a movement. They shared to a remarkable degree, if invarying proportions, the negative and positive features which characterized it: on the onehand criticism, even rejection of traditional authority, especially that of the Church, andon the other a bold and constructive attempt to understand and explain man and theuniverse, and in particular to define man’s place and role in society, both as it was and asit should be. On many topics (such as the origin of life, epistemology, natural law,religious toleration, political freedom), they held broadly similar views and differed onlyin matters of detail. The very term
‘philosophes’ came to be used to designate thethinkers who held these views, and the
philosophes actually saw themselves as a kind ofbrotherhood involved in a campaign, a group of ‘frères’ who shared the same attitudesand aspirations. Many of them were friends, or at least acquaintances, who metfrequently, energetically exchanged ideas on such matters as metaphysics, morality,politics and economics—as well as gossip—and even contributed to each other’s worksin a variety of ways. Quite apart from the
Encyclopédie, edited by Diderot andd’Alembert, which had over 130 contributors, several works were in a sense collectiveventures, embodying the results of discussions within the group—or even, in the case ofRaynal’s
Histoire des deux Indes, actual contributions by different individuals.It has been argued that some of the principal figures of the French Enlightenment werelargely gifted vulgarizers, rather than original thinkers. While this is no doubt anexaggeration, it does draw attention to the way in which they picked up and developedideas that had been expressed by sometimes lone voices in previous centuries.Theythemselves often emphasized their links with the Ancients as a way of stressing theirrejection of Christian tradition, though if their declared hero was Socrates, a morespecific inspiration was probably provided by the materialism and evolutionary ideas ofLucretius. As for the modern world, Montaigne had adopted a relativist anthropologicalapproach to morality two centuries before Montesquieu, and Descartes’s rationalism hadopened the way to the confidence in human reason and the rejection of traditionalauthority: his mechanistic account of man all but excluded the soul, and his mechanisticaccount of the universe all but dispensed with God. Pierre Bayle, a follower of Descartesin his use of reason, had ridiculed superstition (and by implication certain religiousbeliefs) in his
Pensées sur la Comète (1682), which ended with a chapter envisaging, ofall things, the possibility of a society of atheists. In his
Dictionnaire historique et critique(1697), which was to become an arsenal of material for use by Voltaire and others in thebattle against the Church, he applied Cartesian scepticism to history, and moresignificantly, to biblical history. In the field of science, Bacon, a contemporary ofMontaigne, had spelled out an ambitious programme of enquiry, based on investigationand experiment instead of the acceptance of authority, which would be one of the greatinspirations of the
Encyclopédie; and Newton’s huge step forward in explaining the lawsgoverning the universe had made it ever easier to conceive of a world without God,despite his own deep religious convictions. Above all, perhaps, Locke’s account in his
Essay concerning human understanding (1690) of the origin of knowledge and genesis ofthe human faculties provided a starting-point both in content and in methodology forvirtually all Enlightenment thought in this area.It is in any case difficult to draw a precise dividing line between predecessors of theFrench Enlightenment and the movement itself. The very concept of an Enlightenment isno doubt a rather nebulous one, referring to a speeding up, an intensification ofmanifestations of certain currents of thought rather than a new departure. Voltaire (1694–1778), often seen as its most dominant figure, had begun writing long before what isusually thought of as the Enlightenment. Nevertheless his work as a whole couldlegitimately be said to belong to the movement and some of his early individual worksshow many of its characteristics: his
Lettres philosophiques ([9.15]), for example,published in 1734, which introduced Locke and Newton to the French public and praisedEnglish religious toleration and political freedom, implicitly contrasting them with thevery different situation in France. The same could equally be said of the
Lettres Persanesby Montesquieu (1689–1755), a satirical account of French life, politics and religion asseen through the eyes of two Persian visitors, which was published as early as 1721.Nevertheless, it was the 1740s that saw the beginning of the great proliferation of workswhich constitute the French Enlightenment proper, while the movement could be said tohave been brought to a natural close by the outbreak of the French Revolution. In manyways, of course, the Revolution was the outcome of this wave of intellectual attacks onauthority, though retrospectively, the fact that it occurred has inevitably affected the waythe intellectual movement itself is perceived—often as more revolutionary, andparticularly more specifically political, than it actually was.If there was one work which, more than any other, embodied the ideals and attitudes ofthe Enlightenment, it was the
Encyclopédie. The origin of this virtual manifesto of themovement lay in a project to produce a French translation of Chambers’s
Cyclopedia,which had appeared in 1728. Denis Diderot (1713–84)—as yet merely a promising youngwriter, with some repute as a translator—was engaged to do some of the work, but in1747 he was appointed co-editor, along with the distinguished mathematician Jean leRond d’Alembert (1717–83). But from the very beginning, it was Diderot who was thedominant partner and the driving force behind the project. His vision and enthusiasmtransformed it from being a mere translation into a vastly more ambitious enterprise,whose aims were set out in his own Prospectus and subsequent article ‘Encyclopédie’, aswell as in his co-editor’s ‘Discours preliminaire’: they wanted to make known to thepublic at large all the huge strides that had recently been made in human knowledge ofevery conceivable kind, and this comprehensive survey was to be written by appropriateexperts in each field. Diderot and d’Alembert together amassed a veritable army ofcontributors, many of whom were—or were about to be—among the most eminentthinkers and foremost authorities of their day. The first seven volumes of the
Encyclopédie appeared from 1751 to 1759, at which point the work was banned; theremaining ten were published clandestinely in 1765, under the sole editorship of Diderot.Both in its conception and in its execution, the
Encyclopédie reflected the emphaticanthropocentrism that was characteristic of the Enlightenment, and that was expressed inunambiguous terms in Diderot’s article ‘Encyclopédie’: ‘Man is the sole point fromwhich one must start and to which one must bring everything back […] Apart from myexistence and the happiness of my fellow men, what does the rest of nature matter tome?’. Diderot and d’Alembert’s admiration for the capacities and the achievements of thehuman race, their confidence in the progress of civilization, went hand in hand with adeeply felt desire to contribute to that progress and to work for the happiness of mankind.So that an important aspect of the knowledge that the Encyclopedists sought topopularize and disseminate was the critical thinking that was increasingly challengingreceived wisdom and established authority. Human reason was no longer a frail andunreliable prop in a world of mystery, but a sturdy guide in a universe that was graduallybeing understood and an environment that was gradually being mastered. Diderot andd’Alembert and many of their collaborators saw themselves as engaged in a campaign,fighting a battle against the forces of evil for the intellectual and material liberation ofmankind. And this liberation truly involved enlightening men, changing the way theythought, as Diderot made clear in a letter written in 1762: ‘In time this work will certainlybring about a revolution in men’s minds…we shall have served humanity’ ([9.6], 4:172).Inevitably, in its concentration on man, its faith in reason, and its challenge to authority,the
Encyclopédie was setting itself up as inherently opposed to Christianity, whichrequired human reason to submit to authority. In fact, the Church came to be seen bymany
philosophes as the arch enemy of mankind, and in the articles of the
Encyclopédie(as well as in many other works of the period), it was often represented not just as anobstacle to progress, but as a powerful agent of repression and restriction, an instrumentof the forces of darkness which had for centuries sought to submerge the forces ofenlightenment.If Diderot was the principal inspiration of the
Encyclopédie, it was d’Alembert whocould be described as its theoretician. No doubt d’Alembert was not himself a brilliantlyinventive thinker like Diderot; but this very fact helped to make him a representativefigure of the movement. Though the admirably structured syntheses of the “Discourspreliminaire’ of the
Encyclopédie and of the later
Essai sur les Eléments de Philosophie(1759) were d’Alembert’s own, the ideas he was synthesizing represented for the mostpart the generally agreed position of the
philosophes. He described the aims, the rationaleand the methods of the work, expounding what one might describe as the philosophicalstarting point both of the
Encyclopédie and of the Enlightenment as a whole.D’Alembert was very conscious of his philosophical inheritance, of belonging to anembattled élite which had struggled towards enlightenment throughout the centuries andwas only now coming into its own. He saw the history of human thought and endeavouras a never-ending war against oppressive forces, with the flag carried by a few great men,above all Bacon, Descartes, Newton and Locke. The aims of the Enlightenment reflectedin the ‘Discours preliminaire’ were indeed vast—nothing less than an aspiration tounderstand and describe the whole of ‘nature’ and to give an account of every aspect ofhumanknowledge. One of the most fundamental tenets of Enlightenment thought was theoneness of the universe, a principle which had been forcefully propounded the yearbefore the publication of the first volume of the
Encyclopédie in an
Essai de Cosmologieby the gifted mathematician and natural scientist Pierre-Louis Moreau de Maupertuis(1698–1759): ‘There is a universal connection between everything in nature, in the moralas well as in the physical’ (quoted Goyard-Fabre [9.20], 158). D’Alembert argued inmuch the same way that the universe, if only we could understand it, would appear to beone single fact, and that there was some kind of unity underlying all natural phenomena.But his ambitious aims were accompanied by a characteristic humility, a recognition ofthe limitations of the human mind: he accepted, for instance, that first causes were almostalways unknowable, and postulated as the only fruitful philosophical method the attemptto reduce phenomena to the smallest possible number of underlying principles, which hetermed the ‘esprit systématique’. But this method involved first and foremost themeticulous observation of facts, in contrast to the ‘esprit de système’ which had so oftenled thinkers astray with the creation of ingenious rational constructions not based onempirical evidence. To illustrate the point, he quoted the example of the magnet: it was alaudable philosophical enterprise to seek the single principle from which its variousqualities stemmed, but this principle might well remain unknown for a long time. In themeantime, the only way forward lay in the amassing, ordering and cautious analysis ofobservations.The best example of d’Alembert’s organized approach to the ordering of data isperhaps his emphasis in the ‘Discours preliminaire’ on the interrelatedness of humanknowledge. If all phenomena are linked in some way, then all knowledge must besimilarly connected, though if the underlying unity of phenomena remains hidden, thetrue links between different areas of knowledge must remain at best speculative. Whileacknowledging therefore the arbitrariness of such theoretical divisions, he adopted, withslight modifications, the schematic tree of knowledge proposed by Bacon, with its threemain branches the faculties of memory, reason and imagination, linked by the centralstem of the understanding.It may well be argued that the conviction that there is a unity underlying all naturalphenomena and all human knowledge is itself an a priori assumption preceding empiricalobservation, and d’Alembert’s position seems in fact to be a judicious blending ofCartesian rationalism with the emphasis on observation that derived from Newton andLocke. Be that as it may, his approach to the classification of knowledge can be seen bothas pragmatic and, above all, as anthropocentric, in that it is based on human perception ofphenomena rather than ontheir ‘true’ nature. Indeed, his whole discussion of knowledgeis man-centred. He analyses, speculatively, the way in which all kinds of knowledge,from the elements of morality to the arts and sciences, have arisen organically as aresponse to human needs. D’Alembert’s approach to philosophical enquiry is similarlybased on human needs. Philosophy, he says in his
Eléments de philosophie, should not beconcerned with axiomatic truths like ‘the part is smaller than the whole’, since they areself-evident and thus useless; nor with vain metaphysical enquiry into such matters as thenature of movement. The true philosopher sensibly supposes the existence of movementand tries to discover how it operates in practice: our models should be the scientists who,from Archimedes to Newton, have discovered the laws according to which the universefunctions.Now it is true that d’Alembert was primarily a mathematician and physicist rather thana philosopher (though the distinction between philosophy and science in the eighteenthcentury was still rather imprecise), but his mistrust of what he saw as sterile metaphysicalspeculation about absolute reality and his emphasis on the scientific and the utilitarianwere shared by many who were not scientists at all. Thinkers convinced of the ultimateintelligibility of the universe and imbued with confidence in man’s capacities to decode ithad little patience with the metaphysical theories of Spinoza or Leibniz, for example,about such matters as pre-established harmony. The knowledge that interested thethinkers of the Enlightenment was not metaphysical, but scientific, knowledge of thematerial world of nature.Their principal inspiration in this field was undoubtedly Newton. The first writer inFrance to accept and expound his theory of gravitation was Maupertuis, in his
Discourssur les différentes figures des astres, published in 1732, but after Maupertuis, Newtonwas taken up and popularized by Voltaire, particularly in his
Eléments de la philosophiede Newton (1739) ([9.15]), and by the time the first volume of the
Encyclopédie waspublished, the lavish praise bestowed on him by d’Alembert expressed a view which waswidely shared in France.It was above all Newton’s methods which were to serve as a model for scientificinvestigation, the observation of phenomena followed by the attempt to discover theprinciples or laws underlying them. The most cogent exponent of this approach to sciencewas no doubt the Abbe Etienne Bonnot de Condillac (1715–80), perhaps the mostimportant philosopher—as distinct from
philosophe—of the French Enlightenment, andcertainly the most systematic one. In his
Traité des Systèmes, published in 1749,supplemented by the ‘Art de Raisonner’, which formed part of a
Cours d’Etudes (1769–73), he proposed a methodology of science which closely followed Newton. LikeNewton, and like d’Alembert, he conceded that the ultimate reality of things wasinaccess-ible to the human mind, though he did believe both that our perception of theuniverse in some way corresponded to its true reality, and that it was indeed an ordereduniverse, consisting of a vast unified system. Metaphysicians such as Descartes,Malebranche and Leibniz had gone astray because the systems they had proposed werenot based on observation of the natural world: the proper procedure for the scientist wasnot to construct systems, but to seek to discover as many elements as possible of the truesystem of the universe. And the proper method, said Condillac, was the analysis of acombination of two types of evidence, the evidence of fact, based on the observation ofphenomena, and the evidence of reason, based as far as possible on a mathematicalmodel. Newton’s system provided the perfect demonstration of such an approach.However, while there was general agreement that earlier philosopher-scientists hadgone too far in their construction of systems based on a misguided use of hypotheses, itwas beginning to be felt that some disciples of Newton tended to go to the oppositeextreme in their reluctance to venture beyond the observation of phenomena. Mme duChâtelet (Gabrielle-Emilie, Marquise du Châtelet, 1706–49, unjustly better known toposterity as Voltaire’s mistress, but in fact a serious thinker in her own right who waslargely responsible for making the philosophy of Leibniz known in France), in her
Institutions de physique (1740), and Condillac, in the
Traité des Systèmes, both advocatedcaution in the use of hypotheses, but they recognized their value as a part of goodscientific method: used correctly they should serve as a basis for experimentation,suggesting further lines of enquiry in the quest to discover the links between observedphenomena.But Newton was a mathematician, and rather than the abstract field of mathematics, itwas the experimental domain of biological science in which such methods were to bemost productively employed. If there was one work which both embodied the principlesof the new science and paved the way for the great strides it was to make in the nextcentury, it was surely the
Histoire naturelle by Georges-Louis Leclerc, Comte de Buff on(1707–88), which has been compared in its importance to Newton’s
Principiaphilosophiae naturalis (Cassirer [9.16], 104). Buffon’s monumental work, the first threevolumes of which appeared in 1749, broke new ground both in its methods and in itsmatter. To begin with, methodologically, while he remained Newtonian in his emphasison observation and rejection of authority and preconceptions, Buffon helped to liberatescience from the over-restrictive requirement for mathematical type proof by envisaginga new approach to scientific evidence: he saw that the repetition of identical events, forinstance, can lead one to postulate a theory which may not have the certainty ofmathematical proof, but which may legitimately be based on such a degree of probabilitythat it carries, in effect, moral conviction.When Buffon applies such methods to the study of the natural world, his strikinglysecular approach is firmly based on historicity. By considering the evidence of geology(and simply ignoring the Bible), he boldly drew conclusions about the immense age ofthe world. In his vision of an organically evolving universe, there was no room for finalcauses, which he rejected as misleading abstractions inhibiting true scientific enquiry.Whereas the great botanist Linnaeus, his exact contemporary, had a static view of nature,in which all plants and animals were created once and for all in permanent form for theglorification of God, Buffon emphasized the boundless creativity of ‘nature’ (rather thanGod): nature worked on a kind of trial and error basis, with its failures as well as itssuccesses, producing monsters doomed to extinction as well as species equipped tosurvive and prosper by adapting to their environment. He stressed too, in volume two ofthe
Histoire naturelle, the continuity in nature, pointing out that the categories we use tointerpret the world—animal, vegetable, mineral—are merely convenient labels,corresponding only to ‘general ideas’, and that there are in reality no clear-cutdistinctions between them. Thus no actual animal corresponds to the general idea animal,and some are further from it than others: an insect is less of an animal than a dog, anoyster than an insect, and so on through subtle gradations until we come, for example, tothe egg, which is neither animal nor mineral. (‘Histoire générale des animaux’, ch. 8). Asfor man, if Buffon repeatedly emphasized his distance from the animals, this was in nosense a spiritual superiority based on theological arguments. He expressed a confidencein the capacity of human reason to discover ‘the secrets of Nature’ which was entirelycharacteristic of the Enlightenment, and he explained the nobility of man by a soundhistorico-biological demonstration. Man was originally an animal like the others, butendowed with certain characteristics which enabled him to develop in a spectacularfashion: an unusually long period of physical maturation led to the necessary creation ofthe family unit and of society, without which man could never have survived (‘Lesanimaux carnassiers’, [9.2], 7:28–9); it was social life which led to the crucial creation oflanguage, enabling man to preserve the intellectual heritage of his society and benefitfrom the cumulative transmission of knowledge and thought (‘Nomenclature des singes’,[9.2], 14).Clearly Buffon’s view of the universe was in many ways an evolutionary one. It hasbeen argued that his thought was not really transformist, and that he had no true idea ofthe evolution of species [9.29], 577); nevertheless, by placing the study of biology in anhistorical perspective, by his vision of a dynamic, changing, natural world, hecan truly besaid to have anticipated Lamarck and Darwin. But such ideas were in the air. At almostexactly the same time as Buffon, Diderot too, first in his
Lettre sur les Aveugles (1749)and then in the
Pensées sur l’interprétation de la nature (1753), outlined a similarevolutionary account of the animal world ([9.5]): the apparently wonderful way in whichexisting forms of life are adapted to their needs and their environment, far from beingevidence of final causes, is merely the result of a natural process, in which many createdforms turned out to be blind alleys, unable to survive or simply unable to reproduce. It istrue that this theory had been expounded by Lucretius in his
De natura rerum, but its reemergencein the eighteenth century, in the context of post-Bacon post-Newton science,gave it an entirely new significance.However, there was one thinker at this time who went even further along the roadtowards Darwin. Having begun with the same Lucretian theory as Buffon and Diderot,Maupertuis developed it somewhat differently. One of the great scientific controversiesof the period was the debate about the origin of life and procreation, which had beengiven a huge boost by the discoveries of John Needham, who thought he had observedthe spontaneous generation of life in a test-tube. In his
Venus physique (1745),Maupertuis tackled the question of generation by the study of heredity, which, beingobservable, was a distinctly more feasible approach in the eighteenth century than byanatomical research, which was still very unreliable. The transmission of acquiredparental and even ancestral characteristics appeared to confirm the theory that inprocreation the seed came from both parents. When he developed these ideas further inhis
Système de la nature (1751), Maupertuis explained this process of transmission by akind of memory retained by the component parts of the maternal and paternal seed, eachof which comes from a different part of the body and is destined to reproduce a similarpart in the new being. However, chance deviations can then lead to the transformationand multiplication of species:Could one not in this way explain how, starting from two single individuals, themultiplication of the most disparate species could have occurred? They wouldhave owed their origin merely to a few chance productions […]; and as a resultof repeated deviations, there would have come about the infinite diversity ofanimals which we see today.[(
Système de la nature, xlv, quoted Roger [9.29], 484)]Now side by side with these developments in the field of biological science, an evenmore fundamental debate was being conducted about the nature of knowledge and themanner of its acquisition, one of the central issues of Enlightenment thought. The
philosophes attempted earnestly—if not altogether consistently—to apply scientificmethod to the study of epistemology. To say, as d’Alembert had done, that knowledge isacquired in response to human need does not explain precisely how it was acquired:d’Alembert took it for granted that ideas, the building bricks of knowledge, are derivedfrom the sensations, and his views were representative of French thought in the mideighteenthcentury. Descartes’s innate ideas were totally discredited and thesensationalism of Locke was widely accepted. But if there was a general consensusaccepting the broad lines of Locke’s thought, opinions diverged when it came to thedetails, and these divergences were to have far-reaching implications.The doctrine that all our knowledge originates in sense-experience was of course anancient one, going back at least to Aristotle, but its development and analysis in Locke’s
Essay concerning human understanding went far beyond any previous version of it, andcan truly be said to have laid the foundations of modern empirical psychology. There is,though, an inherent ambiguity in the celebrated maxim ‘Nihil in intellectu quod non anteafuerit in sensu’, which might seem to imply a totally materialist explanation of man.Locke did not go this far, and made a very clear distinction between sensation andreflexion, the capacity to organize the experience of the senses, thus retaining the activityof the mind—and the possibility of a spiritual soul. Even so, he had, as it were, opened akind of Pandora’s box, from which escaped not just the extreme doctrine of completematerialism, but also, curiously, what might seem to be its opposite, idealism.If, as Locke argued, all our knowledge comes through our senses, how can we everknow with certainty anything at all about the outside world? How can we even knowwhether it exists, let alone whether it corresponds to our perception of it? In fact,however, this fundamental problem raised by Berkeley seemed to bother the French
philosophes very little. A typical response was Voltaire’s, in his
Traité de métaphysique(written, though not published, about 1734). To begin with, he says, whether or not theexternal world really exists makes absolutely no difference to actual life. He then raises anumber of common-sense objections to idealism, and concludes by declaring that hecannot help being more convinced by the existence of the material world than by many ageometrical truth. D’Alembert too dismissed Berkeleyan idealism with similar ease: if theexternal world
did exist, then we should experience exactly the same sensations as weactually do; therefore, presumably, it does exist. The problem was taken rather moreseriously and discussed at some length in the
Encyclopédie article ‘Existence’, by Turgot,but the principal argument used boils down to saying that by far the most plausible causeof our sensations is the existence of the external world. This down-to-earth resolution of acomplex metaphysical problem was in fact characteristic of the thinkers of theFrenchEnlightenment, whose approach to philosophy was pragmatic and relative,profoundly man-centred. Reliance on the perception of the world by the human sensesseemed a perfectly sound starting point for the kind of enquiry that interested them.Materialism, however, was quite another question, if only because of its implicationsfor morality. At first, most thinkers retained Locke’s dualism, invoking some kind ofinnate, active, non-physical power of the mind which was brought into play by thepassive experience of the physical senses. This, for example, was the position adopted byd’Alembert, who maintained in the ‘Discours Préliminaire’ that the ‘substance’ in uswhich wills and thinks is self-evidently different from matter. But there was an increasing(though still minority) tendency to eliminate Locke’s crucial distinction betweensensation and reflexion, and to see all the operations of the mind as physiologicallydetermined responses to the experience of the senses.This shift away from Locke is to some extent epitomized in the thought of his principalheir, Condillac, who was certainly the most important French eighteenth century thinkerin the field of epistemology (or ‘metaphysics’ as his contemporaries tended to call it). Inhis
Essai sur l’origine des connaissances humaines (1746), Condillac set out to bring agreater precision to the thought of Locke, and consistently with the methodological aimswhich were to be enunciated by d’Alembert, to attempt to reduce the explanation of thehuman understanding ‘to a single principle’—though it is debatable whether hesucceeded in this. In the beginning was the sensation; but our physical needs cause us toexperience pleasure or pain in response to certain sensations, and this creates theimportant phenomenon of attention. In turn, attention leads to the linking of sensations toform the association of ideas (needs are associated with their objects), and the associationof ideas, by enabling a perception to be recalled in the absence of the object which causedit, constitutes the basis of memory. The development of the understanding thus far hasbeen purely passive, an automatic response to outside stimuli, but at this point Condillacenvisages the invention of signs (i.e. language) as the crucial step which endows manwith the faculty of reflexion, the capacity to direct his attention at will, and it is thisfaculty which generates all the higher operations of the mind. As for Berkeley’s idealism,Condillac virtually ignored it, and if he addressed the question of the unreliability of theinformation acquired through the senses, it was merely to point out that the errors ofperception due to one sense can be corrected by recourse to others—thus apparentlyassuming the objective reality of the external world.In the
Essai, Condillac had already taken a substantial step towards a thoroughlymaterialist explanation of man. In contrast to Locke’s sharp distinction between the staticunderstanding, represented as a kind of
tabula rasa on which sense impressions were‘written’, and the innate active power of reflexion, Condillac’s vision of theunderstanding was a dynamic one, conceived as a series of operations, thus facilitating itsconversion to a self-sufficient system. The move towards materialism was taken a stagefurther in his most celebrated work, the
Traité des sensations (1754). The
Traité wasrigorously systematic both in substance and in form. Whereas the
Essai had followedLocke’s dual scheme, retaining reflexion as a separate faculty, the
Traité furthersimplified the explanation of man by making reflexion merely a product of thesensations. But the process of simplification and systematization was facilitated by themethod Condillac used in this work. He imagined a statue which he then endowedsuccessively with the five senses. The idea of a statue being given life as a way ofstudying the awakening of the human consciousness and understanding was notoriginal—Buffon in particular had used it in the Histoire naturelle de l’homme’ (involume 3 of the
Histoire naturelle, published in 1749); but Condillac’s analysis was moresystematic and more acute than Buffon’s. He gave his statue one sense at a time, and witheach sense he explored the range of ideas and feelings it would be able to acquire, firstwith that sense alone, and then, after the first sense, by combining that sense with thosegiven to it previously. He began with the most humble, smell. Endowed with a sense ofsmell alone, the statue is presented with a variety of odours, causing it different degreesof pleasure or discomfort, and leading it to desire, to compare and to judge. However,Condillac notes, it will only experience desire when, as a result of a succession ofsensations, it has realized that ‘it can cease to be what it is and become again what it hasbeen’ (
Traité des sensations, 1, 2, 4, [9.3], 1:225); when, in short, it has begun toremember, and it is the birth of memory which is a similar prerequisite for thedevelopment of comparison and judgement. After the sense of smell comes the turn oftaste, which is dealt with similarly, and so on, through hearing, sight and finally touch.The whole process, from simple sensation to complex, abstract ideas, even to moral andaesthetic judgements, is an automatic one, determined by the interplay of senseimpressions and the capacity for experiencing pleasure and pain. Remembering,reflecting, judging are all analyzed as different ways of being attentive. Judgement, forexample, is the perception of a relationship, an automatic concomitant of comparison; butto compare ‘is nothing other than to give one’s attention to two ideas at the same time’ (1,2, 14–15, [9.3], 1:226).One of the most striking arguments in the
Traité concerned the way in which manbecomes aware of his own existence and of the outside world. Whereas Locke, and morerecently Buffon, had appeared to take it for granted that perception was inseparable fromself-awareness, Condillac maintained that initially, with only one sen-sation, the statuewould have no sense of self at all. Only with a change of sensation, when it becomesaware (through memory, automatic for Condillac) of its own continuity despite thechange, will it discover the concept ‘I’. Even then, it will still necessarily identify with itssensations: it will seem to
be the scent of the rose or the carnation, without anyconsciousness of a self distinct from its modifications. It will not, in other words, beconscious of the existence of a separate outside world which is responsible for causing itssensations. That consciousness will only come with the sense of touch and the experienceof movement. There had long been a debate about the precise relationship between thesenses of sight and touch and their relative importance. Condillac followed Berkeley,who in his
New Theory of Vision (1709) had rejected Descartes’s explanation of ourperception of extension as a kind of intuitive calculation, and demonstrated that it couldonly result from movement. The other senses cannot by themselves convey the awarenessof the outside world; it is only when the statue moves and becomes conscious of anobstacle to its movement that it will deduce the existence of space and otherness.On the other hand, whether or not the ‘real’ outside world corresponded to ourperception of it, whether even it was extended, was a matter on which Condillac wouldnot commit himself. He shared Berkeley’s view that we can know directly only oursensations and could see no evidence for assuming that the qualities we perceive actuallyexist in objects themselves. But this is not a reason for denying the existence of anoutside world: the only sound inference we can draw from the available evidence is that‘bodies are beings which produce sensations in us, and which have properties aboutwhich we can make no sure judgement’ (IV, 5, 1, [9.3], 1:306n.).Condillac’s response to the problem of idealism highlights the ambiguous status of thiskind of epistemological approach to psychology, on the borderline between science andmetaphysics. He may have prided himself on his scientific methodology, but whilst itcould justifiably be described as Newtonian in its quasi-mathematical rigour, it wasscarcely scientific in the sense of empirical or experimental, and this was of course thecase with the sensationalist debate in general. The acute observation and rigorousanalysis of the
Traité focused principally not on live human beings but on animaginatively conceived ideal model. Condillac and his contemporaries did, however,make use of empirical investigation when it was possible. The ideal model itself, as wellas other kinds of sensationalist speculation, must have been based on a good deal oflargely unrecorded observation of real life, and sometimes there were opportunities for amore scientific, even experimental approach. A case in point was the actual functioningof the sense of sight. The English philosopher (and friend of Locke), William Molyneux,had posed the following problem: would a person blind from birth who had learnt todistinguish by touch a cube from a sphere, and who had then had sight restored, be able,by sight alone, to recognize the two objects? Initially the debate was largely theoretical,but when the philosophically inclined London surgeon Cheselden pioneered andperfected the operation for the removal of cataracts, the opportunity was created to moveit on to a more scientific basis: Cheselden’s observation of a person born blind who wasthen given sight, reported in Voltaire’s
Eléments de la philosophie de Newton, appearedto confirm that the interpretation of visual sensations was not intuitive and had to belearned from experience in conjunction with other sense data.Despite the fragility of its scientific foundations, sensationalist psychology reflectedthe spirit of the Enlightenment in being an attempted anatomical (if unproven)explanation of man, which ignored or was positively hostile to the traditional (Christian)explanation—another example of a field of knowledge being removed from the authorityof theology towards (if not quite as far as) science. But there was also an indirect andperhaps more important way in which sensationalist psychology came into conflict withChristianity: it made much easier a totally materialist explanation of man, with the diremoral implications that we shall be examining in the next chapter. The most controversialpoint in sensationalist analyses of the understanding was the degree to which itsoperations were produced by an innate active element. If absolutely all mental processesare automatic, as they appear to be in the
Traité des Sensations, resulting from pleasureandpain-responses to sense impressions, then the mind is merely an extension of thebody: not only is reflexion not an act of the will, but the will itself disappears. ButCondillac was primarily a seeker after truth rather than a
philosophe, and sought, ifanything, to avoid controversy. Others, however, had distinctly more polemicalintentions.One of the most unambiguous expositions of the passivity of the understanding and ofthe will appeared in 1756 in the anonymous article ‘Evidence’, in the sixth volume of the
Encyclopédie; the article was in fact by the physiocrat François Quesnay (1694–1774),though Rousseau, who profoundly disagreed with its central thesis, suspected it had beenwritten by Buffon or Condillac (interesting indeed for his perception of their position inthe matter). Quesnay argued that willing is merely a form of feeling: ‘to want or to bewilling is nothing other than to feel pleasantly; not to want or to be unwilling is similarlynothing other than to feel unpleasantly’. It was this thesis, developed at considerablygreater length, which, two years later, served as the starting point of the scandalous
Del’esprit, by Claude-Adrien Helvetius (1715–71): not only was the book banned, but theoutrage it caused contributed to the definitive banning of the
Encyclopédie itself.Helvetius began by arguing that remembering and even judging are merely forms offeeling, though his demonstration is neither very subtle nor very convincing as he dealswith various possible objections. The central thesis of
De l’esprit was that all minds arepotentially equal, since all men (it is not entirely clear whether Helvetius intends this toinclude women or not) are endowed with the same capacity of attention which can enablethem to attain to the most elevated ideas.Helvétius, it may be argued, makes clear the materialism which had been latent inLocke. But sensationalism was not the only road to materialism, and the scientificprogress discussed earlier also led a number of thinkers in a similar direction. Inparticular, despite Newton’s own views, gravitation came to be seen as a property ofmatter, alongside extent and impenetrability, so that matter was no longer passive, as forDescartes, but capable of moving itself, and this was to provide an obvious basis formaterialist explanations of the world. But the first thoroughgoing materialist of theFrench Enlightenment, subsequently much admired by Marx, was not a physicist but adoctor, Julien Offroy de la Mettrie (1709–51). La Mettrie’s approach was physiological:he extended the mechanism of Descartes to man, and transposed the determinism of theNewtonian universe to the sphere of human psychology.His principal thesis, expounded mainly in his
Histoire naturelle de l’âme (1745),otherwise known as
Traité de l’âme, and developed further in
L’Homme machine (1748),was that all man’s mental functions are physiological in their origin. The
Traité de l’âmeattempts to destroy the case for the spirituality of the soul, arguing that there is noevidence whatsoever to lead one to suppose that the capacity for feeling belongs to asubstance distinct from matter. If movement is an attribute of matter, why should this notalso be true of feeling, thought, and will? Observation and experience confirm that thesoul is material, says La Mettrie, whereas only metaphysical arguments are offered tosupport the contrary view. He admits he cannot understand precisely how matter feelsand thinks, but points out that it is no easier to understand how it moves by itself, whilethe notion of an immaterial soul is even more inconceivable. He cites various exampleswhich demonstrate that the memory can be affected by physical conditions and accidents,proving that it must be part of the material body and ‘completely mechanical’ (
Traité del’âme, ch. 10, X, [9.11], 87), and then goes on to argue that the exercise of liberty issimilarly determined by sensations, and that the judgement is a passive acquiescence inthe truth imposed by ‘the evidence of the sensations’.La Mettrie’s principal point, to which he returns in
L’Homme machine, is that the socalledsoul, which falls asleep with the body and needs food to continue functioning, ismerely a way of talking about certain functions of the body. Man, then, is just anotheranimal. The instinct of animals is a product of their brain and nervous system; man’smore complex behaviour is merely the result of having the most complex brain of all theanimals: ‘So that everything comes from the force of instinct alone, and the sovereigntyof the soul is merely a figment of the imagination’ (
Traité, ch. 11, II, [9.11], 93). Theparallel between man and the other animals is the central theme of
L’Homme machine.Differences of character and mind between men are all physiological in origin, as aredifferences between men and animals: La Mettrie is convinced (wrongly, as we nowknow) that the only thing preventing monkeys from learning to speak is their inadequateorgans. In
L’Homme plante (1748), he went one stage further and extended the similarityof organization to all life forms, pointing out that the characteristics of animals, such asrespiration and nutrition, are also to be found in plants.Now it is clear that writers like Helvetius and La Mettrie were engaged in polemics.The implicit starting-point for both was the rejection not merely of the conventionalChristian position, but of any religious or supernatural explanation of man and theuniverse, and they were consciously replying to the arguments of their adversaries: whenLa Mettrie attacked the doctrine of final causes, for example, together with the associatedargument that the wonders of the universe provide incontrovertible proof of the existenceof God, he was attacking the very foundation of the deism propounded by Voltaire andinitially by Diderot, who for their part were explicitly refuting the arguments of thematerialists. In fact, though atheist-materialists and deists tended to be equally hostile toChristianity, the thought of both has to be understood in the context of the continualdebate that opposed them to each other.It is perhaps in the early works of Diderot that this debate can be seen most clearly.Chiefly, this was because he started out as a deist and rapidly became a materialist. But itwas also because most of what he wrote was in the form of a debate, often expressed asdialogue. It is not always easy, as a consequence, to know with certainty what exactly hisideas were. His writings reveal an endlessly inventive thinker, continually indulging inscientific and philosophical speculation, where the author’s thought is sometimes to befound in the conflicting voices rather than in any single one: he was, in short, more givento raising and discussing difficult questions than to proposing answers. Yet despite theambiguities of his thought, Diderot’s materialism is historically much more significantthan La Mettrie’s. Perhaps because of his somewhat confrontational approach (the title‘L’homme machine’ was surely intended to be provocative), La Mettrie was generallyseen as a rather irresponsible extremist, and remained on the fringe of the philosophicmovement. Diderot, in contrast, largely no doubt because of his role as principal editor ofthe
Encyclopédie, was, more than anyone else, right at its centre, one of its acknowledgedleaders. He was a friend of many of the most important thinkers of his day, meeting themfrequently, mainly at Baron d’Holbach’s house in Paris or his country estate of Grandval,and his later works in particular reflected the energetic discussions and exchanges ofideas that took place round the atheistic Baron’s dinner table.The debate between deism and atheism is quite explicit in Diderot’s first original work,the
Pensées philosophiques (1746), in which alternating ‘Thoughts’ present opposingviews. The debate is a finely balanced one. In answer to the atheist’s denial of God,Diderot proposes the standard deistic recourse to the manifest order and beauty of thephysical world; but immediately afterwards, in response to the deist’s claim that it is asinconceivable that the universe could have come into existence by the chancecombination of atoms as that Homer’s
Iliad could have been produced by a chancecombination of letters, he demonstrates that, taking into account the eternal duration ofmatter and movement, together with the infinity of possible combinations, it would beinconceivable if matter had not, by pure chance, ordered itself into some ‘admirablearrangements’ ([9.5], 1:136).By the time he wrote the
Lettre sur les Aveugles, three years later, he had alreadybegun work on the
Encyclopédie, which helped to bring him into contact with the mostadvanced scientific thought of the age. The apparent uncertainty of the
Pensées nowseemed clearly to have given way to atheism and materialism. Much of the work isdevoted to a discussion of sensationalism, in which Diderot anticipates the techniques ofmodern psychology by using the aberrant (here the blind) to provide clues tounderstanding the normal. Like La Mettrie, he emphatically dismisses the idea of aspiritual soul, declaring that a philosopher blind and deaf from birth trying like Descartesto locate the soul would surely place it not in the pineal gland, but at the tips of thefingers, the source of all his knowledge. But the most direct affirmation of Diderot’smaterialism and atheism is to be found in the centre-piece of the work, Saunderson’s(fictitious) deathbed confession, which is mainly a refutation of the arguments of thedeists. Just as ten years later, in
Candide, Voltaire was to quote the harsh evidence of thereal world against Leibnizian Optimism, so Diderot here cites the real world againstVoltaire’s wonders of the universe proof of deism: the blind Saunderson is a monster,living evidence of disorder in the universe. But in a materialist evocation of evolution, hethen goes on to speculate that in the beginning, there was an abundance of such monsters,destined to disappear because of the inadequacy of their organs, so that only the fitsurvived. And using this biological process as an analogy, he proceeded to hypothesizeabout the world we inhabit, no doubt produced by a similar trial and error series ofcombinations of matter and movement.After the
Lettre sur les Aveugles, which led to his imprisonment as the author of anirreligious book, Diderot’s materialist theories were elaborated, mostly speculatively, inhis correspondence, in a number of
Encyclopédie articles, and in several individualworks, particularly the trilogy known as the
Rêve de d’Alembert. They do not constitute acomplete system, but they do present a corpus of more or less coherent ideas, reflectingconsistent attitudes and a steadily growing preoccupation with biology.The problem of the first cause is resolved once and for all by postulating thatmovement, a kind of energy, is a necessary and permanent attribute of matter—everything in nature is manifestly always in movement—and that matter is eternal. Liked’Alembert, Diderot emphasized the unity of the universe, which he described in the
Encyclopédie article ‘Animal’ as ‘a single, unique machine, in which everything isconnected’. This article indeed attempted to give a unified account of all matter, organicand inorganic. Drawing principally on the ideas of Buffon, it nevertheless wentconsiderably further in getting rid of the divisions between man and other animals,between animals and plants—Diderot quoted Trembley’s recent observations on thefresh-water polyp, which did indeed seem to be neither—and even between animate andinanimate matter.The conviction that there are no true divisions between the different categories innature led Diderot to an idea he flirted with for many years but expressed most explicitlyin the
Rêve de d’Alembert, namely the hypothesis that ‘sensibilité’, the capacity to feel, isa ‘general property of matter’ ([9.5], 2:116). This is not to say, of course, that all matteractually feels; sensibility is active in animals, and perhaps in plants, but inert, in otherwords potential, in inanimate matter. The hypothesis is confirmed for Diderot by the easewith which inanimate matter can cross the borderline to become living—the two obviousexamples being the development of the egg in the process of generation, and the evenmore everyday process of eating: The plants feed on earth, and I feed on theplants’ ([9.5], 2:108).The discussion of the active sentience of animate matter, a major issue in the
Rêve, isin fact firmly based on the most recent developments in contemporary scientific thinking.A group of doctors based in Montpellier, which included not only Théophile de Bordeu(1722–76), one of the interlocutors in the
Rêve, but also the young J.-J. Menuret deChambaud (1739–1815), the
Encyclopédie’s principal contributor in the field ofmedicine, were busy showing that all living matter is inherently sentient, a propertywhich manifests itself in a variety of ways in the animal body, in reflexes, in thespontaneous contraction of muscles and organs, in the digestion—even in the response tostimuli of a muscle actually removed from the body. But if Diderot welcomed suchscientific confirmation of his materialist theories, it still left many questions unanswered.In particular, if the formation of living beings can be explained by the successiveaccumulation of sentient ‘molecules’, how does the sentience of the component partsbecome transformed into a corporate consciousness and identity? Diderot suggests as apossible answer—which is more pleasing by its ingenuity than intellectually satisfying—a parallel between an animal and a swarm of bees clustered on a branch: if one imaginesthem becoming fused together by their legs, they pass from the state of contiguity to thatof continuity, and this new state of the swarm is precisely that of the human body.Passing from physiological sensibility to the more complex operations of the mind,Diderot accepts the standard sensationalist view of man, placing particular importance onthe memory as the crucial factor in converting sensations into thought—though herealized that memory too was a result of physical organization, perhaps, he suggested, akind of vibrating fibre. At the same time, he recognized the inadequacy of the usualaccounts of the transition from physical sensations to thought, of the kind provided byHelvetius. Faced with the problem of explaining how the sensations received byindividual organs come to be co-ordinated, he could only suggest the existence of somekind of central function, a ‘common centre’, which registers all the sensations, but which,being endowed with memory, its own special attribute, makes comparisons and providesthe sense of continuity and of identity. Once again he resorted to an analogy to illuminatehis explanation—though again it is more striking than philosophically enlightening: justas a spider at the centre of its web is immediately aware of the slightest movement in anyof its strands, so the ‘common centre’ is informed of the impressions received in any partof the body by means of a ‘network of imperceptible threads’ ([9.5], 2:141).As ever with Diderot, it is difficult to know how literally he means us to take theanalogy, but it is clear that he believed in the existence of a ‘mind’ separate from thesensations. It is equally clear, though, that thought was for him a totally physiologicalfunction, an automatically determined result of sense impressions, however complex theprocess might be. His own view of man was no doubt more subtle than Helvétius’s, but itwas certainly no less materialist and no less determinist, and if he found Helvétius’sdemonstration that judgement and will are merely forms of feeling simplistic, he none theless shared his conclusion that freedom was an illusion. The eponymous hero of Diderot’snovel
Jacques le fataliste (written during the 1770s), clearly here the author’smouthpiece, was convinced that all our behaviour is determined by a necessary (ifimmensely complicated) series of physical causes and effects. So that the will is the resultof conditioning, nothing but ‘the last result of everything one has been since birth up tothe present moment of existence’ ([9.5], 2:175). As Diderot had explained in 1756 in aletter to the author Landois, ‘the word “freedom” is devoid of meaning; there are no freebeings, nor can there be’. If we acquire the illusion of freedom, it is partly because of the‘prodigious variety of our actions’, but mainly because we are in fact conditioned by ourexperience to believe that we are free ([9.5], 19:435–6).Because Diderot’s materialist and determinist theories are often presented as tentative,and in the context of a debate, they contrive to appear less dogmatic and distinctly moresubtle than those of some of his contemporaries. Yet they offer some striking similaritieswith the thought of d’Holbach, which is so lacking in subtlety that at least one modernhistorian of ideas has dismissed it as little more than crude anti-religious propaganda(Goyard-Fabre [9.21], 159). The two men were indeed close friends, and Diderot’scorrespondence bears witness to frequent lively discussions and arguments betweenthem: there seems good reason to suppose both considerable mutual influence, and agreater identity of thought than is usually allowed.The aggressively atheistic philosophy of Paul Thiry, Baron d’Holbach (1723–89),presented in a number of works but principally in the
Système de la Nature (1770), ismore comprehensive and more overt than that of either La Mettrie or Helvetius. He givesan unambiguous (if wordy and repetitive) account of a totally materialist position, anintegrated ‘system’ in which all things, matter, the universe, man, society andgovernment, form part of a cause-and-effect chain of necessity. D’Holbach’s universe is,like Diderot’s, an ever-changing one, with suns and planets continually dying and beingborn. It is composed of matter, which is eternal and eternally and necessarily inmovement, behaving according to fixed laws, such as what d’Holbach calls‘conservation’ (Newton’s inertia), though he recognizes that not all these laws are yetunderstood. This is something he stresses repeatedly: everything that is and happens, isand happens necessarily, and if we see what appears to be evidence of chance, or stillworse, of supernatural forces, it is because we do not understand the true links in thecause-effect chain—d’Holbach invokes the scientific explanations of the miracles andmarvels of the past, such as earthquakes and meteors, and looks forward to a time whenposterity will unravel still more of the secrets of nature.Animate beings, since they are composed of matter, necessarily follow the samephysical laws as the rest of the universe: plants and animals are made up of anaggregation of parts, held together by‘attraction continuelle’. And since the moral is onlya different way of considering the physical, man as a moral being, too, is subject to thesame rule of necessity and follows the same laws of nature. D’Holbach is careful to pointout, however, that when he speaks thus of ‘laws of nature’, it is no more than aconvenient way of referring to the ‘essence’ of things, by which he means the necessaryresult of the properties they possess. It is of the essence of a stone to fall, and similarly, ofthe essence of a sentient being to seek pleasure and to avoid pain. The law of inertia or‘conservation’ affecting all matter becomes self-preservation or self-love in man.Anticipating Diderot’s determinist Jacques, d’Holbach thus saw the life of a man as ‘along sequence of necessary and connected movements’ ([9.10], 1:71), caused by hisphysiology and its interaction with his environment. All the intellectual ‘faculties’ arederived from the faculty of sentience, and d’Holbach’s explanation of sentience isreminiscent of La Mettrie’s: it is ‘a consequence of the essence and properties of animatebeings’ just as gravity and magnetism are of other bodies, and no more (or less)inexplicable ([9.10], 1:102). But like Diderot, he points to the ease with which inanimatematter such as milk and bread can become animate through the simple process ofingestion, and discusses the possibility that, as ‘some philosophers think’, sentience maybe a universal quality of all matter, ‘live’ or ‘inert’ as the case may be ([9.10], 1:104).D’Holbach uses the same analogy as Diderot of the spider in its web to explain howthe brain acts as the co-ordinator of sense data from different parts of the body, at thesame time denying that it has any autonomous activity. Even more than Diderot, andrecalling rather Helvetius and La Mettrie, he emphasizes the physicality of the so-calledsoul, demonstrating that thinking and even willing are only forms of feeling, automaticdespite all appearances to the contrary. To will is to be disposed to action: thus, ‘the sightof fruit on a tree modifies my brain in such a way that it causes my arm to move to pickthe fruit’ ([9.10], 1:115).D’Holbach, however, was just as aware as Diderot of the implications for morality ofthe denial of human freedom, and it is in truth misleading in both their cases to considertheir scientific materialism and determinism separately from their moral and politicalthought. However great the interest of both these thinkers in science, their principalpreoccupations were with man as a moral and social being, and this, rather than onscientific grounds, was why they were hostile to Christianity. Both of them sawChristianity as fundamentally anti-human and therefore as a force for social evil, andtheir materialist-based atheism was as much a consequence of this hostility as a cause ofit. The priorities shared by Diderot and d’Holbach were in fact characteristic of theFrench Enlightenment in general. The move towards a greater understanding of theuniverse triggered by the discoveries of Newton, the development of a scientific approachto the understanding of human psychology stemming mainly from Locke, the enormousstrides that were being made in the understanding of the animal world due to the work ofBuffon and other contemporary naturalists and scientists, all this led to a new andexciting vision of the world, in which authority (especially that of religion) no longerheld sway and every territory was available for exploration. But once the old certaintieswere dethroned, frightening possibilities were laid bare, and to thinkers who were aboveall anthropocentric in their concerns, it might well seem that there were far more pressingmatters to be examined than, for example, the structure of the universe, the differencesbetween animate and inanimate matter, or even the origin of life. It had become essentialto re-examine the very fundamentals of human life, the nature of morality and the rulesgoverning human behaviour and social organization, and it is to the discussion of thesethat the next chapter is principally devoted.
BIBLIOGRAPHYEighteenth-century Works9.1 d’Alembert, Jean le Rond
Essai sur les Elements de Philosophie, ed. R.N. Schwab,Hildesheim, Olms, 1965.9.2 Buffon, Georges-Louis Leclerc, Comte de
Histoire naturelle, Paris, 1749–1804.9.3 Condillac, Abbé Etienne Bonnot de
Oeuvres philosophiques, ed. Le Roy, 3 vols,Corpus Général des philosophes français, Paris, Presses Universitaires, 1947–51.9.4——
Cours d’Etudes, Parma, 1769–73.9.5 Diderot, Denis
Oeuvres complètes, ed. J.Assezat and M.Tourneux, Paris, GarnierFrères, 1875–7.9.6——
Correspondance, ed. G.Roth and J.Varloot, Paris, Editions de Minuit, 1955–70.9.7 du Châtelet, Mme Gabrielle-Emilie
Institutions de physique, London, 1741.9.8
Encyclopédie, ed. Diderot and d’Alembert, Paris, 1751–80.9.9 Helvetius, Claude-Adrien
De l’esprit, Marabout-Universite, Verviers, Gerard, 1973.9.10 d’Holbach, Paul Thiry, Baron
Le Système de la Nature, London, 1770, SlatkineReprints, Geneva, 1973.9.11 la Mettrie, Julien Offroy de
Textes choisis, Les Classiques du peuple, Paris, Editionssociales, 1954.9.12 Maupertuis, Pierre-Louis Moreau de
Oeuvres, Lyon, 1768.9.13 Raynal, Guillaume
Histoire philosophique et politique des deux Indes, Geneva,1780.9.14 Rousseau, Jean-Jacques
Oeuvres complètes, Bibliothèque de la Pléiade, Paris,Gallimard, 1959–69.9.15 Voltaire,
Oeuvres complètes, ed. L.Moland, Paris, Garnier, 1877–85.9.16——
Traite de métaphysique, ed. H.T.Patterson, Manchester, Manchester UniversityPress, 1937.
General Surveys9.16 Cassirer, E.
The Philosophy of the Enlightenment, trans. F.C.A.Koellen andJ.P.Pettegrove, Princeton, NJ, Princeton University Press, 1951.9.17 Crocker, L.G.
An Age of Crisis, Baltimore, John Hopkins Press, 1959.9.18——
Nature and Culture, ethical thought in eighteenth century France, Baltimore,John Hopkins Press, 1963.9.19 Gay, P.
The Enlightenment: an interpretation, 2 vols, London, Weidenfeld andNicolson, 1966–9.9.20 Goyard-Fabre, S.
La philosophie des lumières en France, Paris, Klincksieck, 1972.
Critical Studies on Aspects of the French Enlightenment and Individual Authors9.21 Crocker, L.G.
Diderot’s chaotic order: approach to synthesis, Princeton, NJ,Princeton University Press, 1974.9.22——
Diderot the embattled philosopher, London, N.Spearman, 1955.9.23 Duchet, M.
Anthropologie et Histoire au siècle de lumières, Paris, Maspero, 1971.9.24 France, P.
Diderot, (Past Masters) Oxford, Oxford University Press, 1983.9.25 Hermand, P.
Les idées morales de Diderot, Paris, Presses Universitaires, 1923.9.26 Knight, I.F.
The Geometric spirit: the Abbé de Condillac and the FrenchEnlightenment, New Haven and London, Yale University Press, 1968.9.27 Lefèbvre, H.
Diderot, Paris, Editeurs Réunis, 1949.9.28 Proust, J.
Diderot et l’Encyclopedie, Paris, A.Colin, 1962.9.29 Roger, J.
Les Sciences de la vie dans la pensee française du XVIIIe siècle, 2eedition, Paris, A.Colin, 1971.There are also numerous relevant articles in the following specialist journals:9.30
Diderot Studies, Syracuse, then Geneva, Droz, 1949–.9.31
Studies on Voltaire and the Eighteenth Century, Geneva, then Oxford, 1955–.