Enlightenment I (The French): science, materialism and determinism

The French Enlightenment I: science, materialism and determinism Peter Jimack The French Enlightenment is not just a convenient label devised by historians of philosophy, and the thinkers to be discussed in this chapter and the next were for the most part conscious of belonging to a movement. They shared to a remarkable degree, if in varying proportions, the negative and positive features which characterized it: on the one hand criticism, even rejection of traditional authority, especially that of the Church, and on the other a bold and constructive attempt to understand and explain man and the universe, and in particular to define man’s place and role in society, both as it was and as it 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 only in matters of detail. The very term ‘philosophes’ came to be used to designate the thinkers who held these views, and the philosophes actually saw themselves as a kind of brotherhood involved in a campaign, a group of ‘frères’ who shared the same attitudes and aspirations. Many of them were friends, or at least acquaintances, who met frequently, energetically exchanged ideas on such matters as metaphysics, morality, politics and economics—as well as gossip—and even contributed to each other’s works in a variety of ways. Quite apart from the Encyclopédie, edited by Diderot and d’Alembert, which had over 130 contributors, several works were in a sense collective ventures, embodying the results of discussions within the group—or even, in the case of Raynal’s Histoire des deux Indes, actual contributions by different individuals. It has been argued that some of the principal figures of the French Enlightenment were largely gifted vulgarizers, rather than original thinkers. While this is no doubt an exaggeration, it does draw attention to the way in which they picked up and developed ideas that had been expressed by sometimes lone voices in previous centuries. They themselves often emphasized their links with the Ancients as a way of stressing their rejection of Christian tradition, though if their declared hero was Socrates, a more specific inspiration was probably provided by the materialism and evolutionary ideas of Lucretius. As for the modern world, Montaigne had adopted a relativist anthropological approach to morality two centuries before Montesquieu, and Descartes’s rationalism had opened the way to the confidence in human reason and the rejection of traditional authority: his mechanistic account of man all but excluded the soul, and his mechanistic account of the universe all but dispensed with God. Pierre Bayle, a follower of Descartes in his use of reason, had ridiculed superstition (and by implication certain religious beliefs) in his Pensées sur la Comète (1682), which ended with a chapter envisaging, of all 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 the battle against the Church, he applied Cartesian scepticism to history, and more significantly, to biblical history. In the field of science, Bacon, a contemporary of Montaigne, had spelled out an ambitious programme of enquiry, based on investigation and experiment instead of the acceptance of authority, which would be one of the great inspirations of the Encyclopédie; and Newton’s huge step forward in explaining the laws governing 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 of the human faculties provided a starting-point both in content and in methodology for virtually all Enlightenment thought in this area. It is in any case difficult to draw a precise dividing line between predecessors of the French Enlightenment and the movement itself. The very concept of an Enlightenment is no doubt a rather nebulous one, referring to a speeding up, an intensification of manifestations 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 is usually thought of as the Enlightenment. Nevertheless his work as a whole could legitimately be said to belong to the movement and some of his early individual works show many of its characteristics: his Lettres philosophiques ([9.15]), for example, published in 1734, which introduced Locke and Newton to the French public and praised English religious toleration and political freedom, implicitly contrasting them with the very different situation in France. The same could equally be said of the Lettres Persanes by Montesquieu (1689–1755), a satirical account of French life, politics and religion as seen 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 works which constitute the French Enlightenment proper, while the movement could be said to have been brought to a natural close by the outbreak of the French Revolution. In many ways, of course, the Revolution was the outcome of this wave of intellectual attacks on authority, though retrospectively, the fact that it occurred has inevitably affected the way the intellectual movement itself is perceived—often as more revolutionary, and particularly more specifically political, than it actually was. If there was one work which, more than any other, embodied the ideals and attitudes of the Enlightenment, it was the Encyclopédie. The origin of this virtual manifesto of the movement 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 young writer, with some repute as a translator—was engaged to do some of the work, but in 1747 he was appointed co-editor, along with the distinguished mathematician Jean le Rond d’Alembert (1717–83). But from the very beginning, it was Diderot who was the dominant partner and the driving force behind the project. His vision and enthusiasm transformed 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’, as well as in his co-editor’s ‘Discours preliminaire’: they wanted to make known to the public at large all the huge strides that had recently been made in human knowledge of every conceivable kind, and this comprehensive survey was to be written by appropriate experts in each field. Diderot and d’Alembert together amassed a veritable army of contributors, many of whom were—or were about to be—among the most eminent thinkers 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; the remaining ten were published clandestinely in 1765, under the sole editorship of Diderot. Both in its conception and in its execution, the Encyclopédie reflected the emphatic anthropocentrism that was characteristic of the Enlightenment, and that was expressed in unambiguous terms in Diderot’s article ‘Encyclopédie’: ‘Man is the sole point from which one must start and to which one must bring everything back […] Apart from my existence and the happiness of my fellow men, what does the rest of nature matter to me?’. Diderot and d’Alembert’s admiration for the capacities and the achievements of the human race, their confidence in the progress of civilization, went hand in hand with a deeply 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 to popularize and disseminate was the critical thinking that was increasingly challenging received wisdom and established authority. Human reason was no longer a frail and unreliable prop in a world of mystery, but a sturdy guide in a universe that was gradually being understood and an environment that was gradually being mastered. Diderot and d’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 of mankind. And this liberation truly involved enlightening men, changing the way they thought, as Diderot made clear in a letter written in 1762: ‘In time this work will certainly bring 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, which required human reason to submit to authority. In fact, the Church came to be seen by many 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 an obstacle to progress, but as a powerful agent of repression and restriction, an instrument of the forces of darkness which had for centuries sought to submerge the forces of enlightenment. If Diderot was the principal inspiration of the Encyclopédie, it was d’Alembert who could be described as its theoretician. No doubt d’Alembert was not himself a brilliantly inventive thinker like Diderot; but this very fact helped to make him a representative figure of the movement. Though the admirably structured syntheses of the “Discours preliminaire’ 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 most part the generally agreed position of the philosophes. He described the aims, the rationale and the methods of the work, expounding what one might describe as the philosophical starting point both of the Encyclopédie and of the Enlightenment as a whole. D’Alembert was very conscious of his philosophical inheritance, of belonging to an embattled élite which had struggled towards enlightenment throughout the centuries and was only now coming into its own. He saw the history of human thought and endeavour as 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 reflected in the ‘Discours preliminaire’ were indeed vast—nothing less than an aspiration to understand and describe the whole of ‘nature’ and to give an account of every aspect of humanknowledge. One of the most fundamental tenets of Enlightenment thought was the oneness of the universe, a principle which had been forcefully propounded the year before the publication of the first volume of the Encyclopédie in an Essai de Cosmologie by the gifted mathematician and natural scientist Pierre-Louis Moreau de Maupertuis (1698–1759): ‘There is a universal connection between everything in nature, in the moral as well as in the physical’ (quoted Goyard-Fabre [9.20], 158). D’Alembert argued in much the same way that the universe, if only we could understand it, would appear to be one 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 of the limitations of the human mind: he accepted, for instance, that first causes were almost always unknowable, and postulated as the only fruitful philosophical method the attempt to reduce phenomena to the smallest possible number of underlying principles, which he termed the ‘esprit systématique’. But this method involved first and foremost the meticulous observation of facts, in contrast to the ‘esprit de système’ which had so often led thinkers astray with the creation of ingenious rational constructions not based on empirical evidence. To illustrate the point, he quoted the example of the magnet: it was a laudable philosophical enterprise to seek the single principle from which its various qualities stemmed, but this principle might well remain unknown for a long time. In the meantime, the only way forward lay in the amassing, ordering and cautious analysis of observations. The best example of d’Alembert’s organized approach to the ordering of data is perhaps his emphasis in the ‘Discours preliminaire’ on the interrelatedness of human knowledge. If all phenomena are linked in some way, then all knowledge must be similarly connected, though if the underlying unity of phenomena remains hidden, the true links between different areas of knowledge must remain at best speculative. While acknowledging therefore the arbitrariness of such theoretical divisions, he adopted, with slight modifications, the schematic tree of knowledge proposed by Bacon, with its three main branches the faculties of memory, reason and imagination, linked by the central stem of the understanding. It may well be argued that the conviction that there is a unity underlying all natural phenomena and all human knowledge is itself an a priori assumption preceding empirical observation, and d’Alembert’s position seems in fact to be a judicious blending of Cartesian rationalism with the emphasis on observation that derived from Newton and Locke. Be that as it may, his approach to the classification of knowledge can be seen both as pragmatic and, above all, as anthropocentric, in that it is based on human perception of phenomena rather than ontheir ‘true’ nature. Indeed, his whole discussion of knowledge is 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 a response to human needs. D’Alembert’s approach to philosophical enquiry is similarly based on human needs. Philosophy, he says in his Eléments de philosophie, should not be concerned with axiomatic truths like ‘the part is smaller than the whole’, since they are self-evident and thus useless; nor with vain metaphysical enquiry into such matters as the nature of movement. The true philosopher sensibly supposes the existence of movement and 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 universe functions. Now it is true that d’Alembert was primarily a mathematician and physicist rather than a philosopher (though the distinction between philosophy and science in the eighteenth century was still rather imprecise), but his mistrust of what he saw as sterile metaphysical speculation about absolute reality and his emphasis on the scientific and the utilitarian were shared by many who were not scientists at all. Thinkers convinced of the ultimate intelligibility of the universe and imbued with confidence in man’s capacities to decode it had little patience with the metaphysical theories of Spinoza or Leibniz, for example, about such matters as pre-established harmony. The knowledge that interested the thinkers of the Enlightenment was not metaphysical, but scientific, knowledge of the material world of nature. Their principal inspiration in this field was undoubtedly Newton. The first writer in France to accept and expound his theory of gravitation was Maupertuis, in his Discours sur les différentes figures des astres, published in 1732, but after Maupertuis, Newton was taken up and popularized by Voltaire, particularly in his Eléments de la philosophie de Newton (1739) ([9.15]), and by the time the first volume of the Encyclopédie was published, the lavish praise bestowed on him by d’Alembert expressed a view which was widely shared in France. It was above all Newton’s methods which were to serve as a model for scientific investigation, the observation of phenomena followed by the attempt to discover the principles or laws underlying them. The most cogent exponent of this approach to science was no doubt the Abbe Etienne Bonnot de Condillac (1715–80), perhaps the most important philosopher—as distinct from philosophe—of the French Enlightenment, and certainly 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. Like Newton, and like d’Alembert, he conceded that the ultimate reality of things was inaccess-ible to the human mind, though he did believe both that our perception of the universe in some way corresponded to its true reality, and that it was indeed an ordered universe, consisting of a vast unified system. Metaphysicians such as Descartes, Malebranche and Leibniz had gone astray because the systems they had proposed were not based on observation of the natural world: the proper procedure for the scientist was not to construct systems, but to seek to discover as many elements as possible of the true system of the universe. And the proper method, said Condillac, was the analysis of a combination of two types of evidence, the evidence of fact, based on the observation of phenomena, and the evidence of reason, based as far as possible on a mathematical model. Newton’s system provided the perfect demonstration of such an approach. However, while there was general agreement that earlier philosopher-scientists had gone too far in their construction of systems based on a misguided use of hypotheses, it was beginning to be felt that some disciples of Newton tended to go to the opposite extreme in their reluctance to venture beyond the observation of phenomena. Mme du Châtelet (Gabrielle-Emilie, Marquise du Châtelet, 1706–49, unjustly better known to posterity as Voltaire’s mistress, but in fact a serious thinker in her own right who was largely responsible for making the philosophy of Leibniz known in France), in her Institutions de physique (1740), and Condillac, in the Traité des Systèmes, both advocated caution in the use of hypotheses, but they recognized their value as a part of good scientific method: used correctly they should serve as a basis for experimentation, suggesting further lines of enquiry in the quest to discover the links between observed phenomena. But Newton was a mathematician, and rather than the abstract field of mathematics, it was the experimental domain of biological science in which such methods were to be most productively employed. If there was one work which both embodied the principles of the new science and paved the way for the great strides it was to make in the next century, 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 Principia philosophiae naturalis (Cassirer [9.16], 104). Buffon’s monumental work, the first three volumes of which appeared in 1749, broke new ground both in its methods and in its matter. To begin with, methodologically, while he remained Newtonian in his emphasis on observation and rejection of authority and preconceptions, Buffon helped to liberate science from the over-restrictive requirement for mathematical type proof by envisaging a new approach to scientific evidence: he saw that the repetition of identical events, for instance, can lead one to postulate a theory which may not have the certainty of mathematical proof, but which may legitimately be based on such a degree of probability that it carries, in effect, moral conviction. When Buffon applies such methods to the study of the natural world, his strikingly secular 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 of the world. In his vision of an organically evolving universe, there was no room for final causes, 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 the glorification of God, Buffon emphasized the boundless creativity of ‘nature’ (rather than God): nature worked on a kind of trial and error basis, with its failures as well as its successes, producing monsters doomed to extinction as well as species equipped to survive and prosper by adapting to their environment. He stressed too, in volume two of the Histoire naturelle, the continuity in nature, pointing out that the categories we use to interpret the world—animal, vegetable, mineral—are merely convenient labels, corresponding only to ‘general ideas’, and that there are in reality no clear-cut distinctions 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, an oyster than an insect, and so on through subtle gradations until we come, for example, to the egg, which is neither animal nor mineral. (‘Histoire générale des animaux’, ch. 8). As for man, if Buffon repeatedly emphasized his distance from the animals, this was in no sense a spiritual superiority based on theological arguments. He expressed a confidence in the capacity of human reason to discover ‘the secrets of Nature’ which was entirely characteristic of the Enlightenment, and he explained the nobility of man by a sound historico-biological demonstration. Man was originally an animal like the others, but endowed with certain characteristics which enabled him to develop in a spectacular fashion: an unusually long period of physical maturation led to the necessary creation of the family unit and of society, without which man could never have survived (‘Les animaux carnassiers’, [9.2], 7:28–9); it was social life which led to the crucial creation of language, enabling man to preserve the intellectual heritage of his society and benefit from 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 has been argued that his thought was not really transformist, and that he had no true idea of the evolution of species [9.29], 577); nevertheless, by placing the study of biology in an historical perspective, by his vision of a dynamic, changing, natural world, hecan truly be said to have anticipated Lamarck and Darwin. But such ideas were in the air. At almost exactly 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 similar evolutionary account of the animal world ([9.5]): the apparently wonderful way in which existing forms of life are adapted to their needs and their environment, far from being evidence of final causes, is merely the result of a natural process, in which many created forms turned out to be blind alleys, unable to survive or simply unable to reproduce. It is true that this theory had been expounded by Lucretius in his De natura rerum, but its reemergence in 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 road towards Darwin. Having begun with the same Lucretian theory as Buffon and Diderot, Maupertuis developed it somewhat differently. One of the great scientific controversies of the period was the debate about the origin of life and procreation, which had been given a huge boost by the discoveries of John Needham, who thought he had observed the 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, being observable, was a distinctly more feasible approach in the eighteenth century than by anatomical research, which was still very unreliable. The transmission of acquired parental and even ancestral characteristics appeared to confirm the theory that in procreation the seed came from both parents. When he developed these ideas further in his Système de la nature (1751), Maupertuis explained this process of transmission by a kind of memory retained by the component parts of the maternal and paternal seed, each of which comes from a different part of the body and is destined to reproduce a similar part in the new being. However, chance deviations can then lead to the transformation and multiplication of species: Could one not in this way explain how, starting from two single individuals, the multiplication of the most disparate species could have occurred? They would have owed their origin merely to a few chance productions […]; and as a result of repeated deviations, there would have come about the infinite diversity of animals 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 even more fundamental debate was being conducted about the nature of knowledge and the manner of its acquisition, one of the central issues of Enlightenment thought. The philosophes attempted earnestly—if not altogether consistently—to apply scientific method to the study of epistemology. To say, as d’Alembert had done, that knowledge is acquired 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 derived from the sensations, and his views were representative of French thought in the mideighteenth century. Descartes’s innate ideas were totally discredited and the sensationalism of Locke was widely accepted. But if there was a general consensus accepting the broad lines of Locke’s thought, opinions diverged when it came to the details, and these divergences were to have far-reaching implications. The doctrine that all our knowledge originates in sense-experience was of course an ancient 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, and can 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 antea fuerit 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 and reflexion, the capacity to organize the experience of the senses, thus retaining the activity of the mind—and the possibility of a spiritual soul. Even so, he had, as it were, opened a kind of Pandora’s box, from which escaped not just the extreme doctrine of complete materialism, 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 ever know with certainty anything at all about the outside world? How can we even know whether 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 the external world really exists makes absolutely no difference to actual life. He then raises a number of common-sense objections to idealism, and concludes by declaring that he cannot help being more convinced by the existence of the material world than by many a geometrical truth. D’Alembert too dismissed Berkeleyan idealism with similar ease: if the external world did exist, then we should experience exactly the same sensations as we actually do; therefore, presumably, it does exist. The problem was taken rather more seriously 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 cause of our sensations is the existence of the external world. This down-to-earth resolution of a complex metaphysical problem was in fact characteristic of the thinkers of the FrenchEnlightenment, whose approach to philosophy was pragmatic and relative, profoundly man-centred. Reliance on the perception of the world by the human senses seemed a perfectly sound starting point for the kind of enquiry that interested them. Materialism, however, was quite another question, if only because of its implications for morality. At first, most thinkers retained Locke’s dualism, invoking some kind of innate, active, non-physical power of the mind which was brought into play by the passive experience of the physical senses. This, for example, was the position adopted by d’Alembert, who maintained in the ‘Discours Préliminaire’ that the ‘substance’ in us which wills and thinks is self-evidently different from matter. But there was an increasing (though still minority) tendency to eliminate Locke’s crucial distinction between sensation and reflexion, and to see all the operations of the mind as physiologically determined responses to the experience of the senses. This shift away from Locke is to some extent epitomized in the thought of his principal heir, Condillac, who was certainly the most important French eighteenth century thinker in the field of epistemology (or ‘metaphysics’ as his contemporaries tended to call it). In his Essai sur l’origine des connaissances humaines (1746), Condillac set out to bring a greater precision to the thought of Locke, and consistently with the methodological aims which were to be enunciated by d’Alembert, to attempt to reduce the explanation of the human understanding ‘to a single principle’—though it is debatable whether he succeeded in this. In the beginning was the sensation; but our physical needs cause us to experience pleasure or pain in response to certain sensations, and this creates the important phenomenon of attention. In turn, attention leads to the linking of sensations to form the association of ideas (needs are associated with their objects), and the association of ideas, by enabling a perception to be recalled in the absence of the object which caused it, constitutes the basis of memory. The development of the understanding thus far has been purely passive, an automatic response to outside stimuli, but at this point Condillac envisages the invention of signs (i.e. language) as the crucial step which endows man with the faculty of reflexion, the capacity to direct his attention at will, and it is this faculty 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 the information acquired through the senses, it was merely to point out that the errors of perception due to one sense can be corrected by recourse to others—thus apparently assuming the objective reality of the external world. In the Essai, Condillac had already taken a substantial step towards a thoroughly materialist explanation of man. In contrast to Locke’s sharp distinction between the static understanding, represented as a kind of tabula rasa on which sense impressions were ‘written’, and the innate active power of reflexion, Condillac’s vision of the understanding was a dynamic one, conceived as a series of operations, thus facilitating its conversion to a self-sufficient system. The move towards materialism was taken a stage further in his most celebrated work, the Traité des sensations (1754). The Traité was rigorously systematic both in substance and in form. Whereas the Essai had followed Locke’s dual scheme, retaining reflexion as a separate faculty, the Traité further simplified the explanation of man by making reflexion merely a product of the sensations. But the process of simplification and systematization was facilitated by the method Condillac used in this work. He imagined a statue which he then endowed successively with the five senses. The idea of a statue being given life as a way of studying the awakening of the human consciousness and understanding was not original—Buffon in particular had used it in the Histoire naturelle de l’homme’ (in volume 3 of the Histoire naturelle, published in 1749); but Condillac’s analysis was more systematic and more acute than Buffon’s. He gave his statue one sense at a time, and with each sense he explored the range of ideas and feelings it would be able to acquire, first with that sense alone, and then, after the first sense, by combining that sense with those given to it previously. He began with the most humble, smell. Endowed with a sense of smell alone, the statue is presented with a variety of odours, causing it different degrees of 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 of sensations, it has realized that ‘it can cease to be what it is and become again what it has been’ (Traité des sensations, 1, 2, 4, [9.3], 1:225); when, in short, it has begun to remember, and it is the birth of memory which is a similar prerequisite for the development of comparison and judgement. After the sense of smell comes the turn of taste, 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 and aesthetic judgements, is an automatic one, determined by the interplay of sense impressions and the capacity for experiencing pleasure and pain. Remembering, reflecting, judging are all analyzed as different ways of being attentive. Judgement, for example, is the perception of a relationship, an automatic concomitant of comparison; but to 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 man becomes aware of his own existence and of the outside world. Whereas Locke, and more recently Buffon, had appeared to take it for granted that perception was inseparable from self-awareness, Condillac maintained that initially, with only one sen-sation, the statue would have no sense of self at all. Only with a change of sensation, when it becomes aware (through memory, automatic for Condillac) of its own continuity despite the change, will it discover the concept ‘I’. Even then, it will still necessarily identify with its sensations: it will seem to be the scent of the rose or the carnation, without any consciousness of a self distinct from its modifications. It will not, in other words, be conscious of the existence of a separate outside world which is responsible for causing its sensations. That consciousness will only come with the sense of touch and the experience of movement. There had long been a debate about the precise relationship between the senses 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 our perception of extension as a kind of intuitive calculation, and demonstrated that it could only result from movement. The other senses cannot by themselves convey the awareness of the outside world; it is only when the statue moves and becomes conscious of an obstacle 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 our perception of it, whether even it was extended, was a matter on which Condillac would not commit himself. He shared Berkeley’s view that we can know directly only our sensations and could see no evidence for assuming that the qualities we perceive actually exist in objects themselves. But this is not a reason for denying the existence of an outside 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 about which 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 this kind of epistemological approach to psychology, on the borderline between science and metaphysics. He may have prided himself on his scientific methodology, but whilst it could justifiably be described as Newtonian in its quasi-mathematical rigour, it was scarcely scientific in the sense of empirical or experimental, and this was of course the case with the sensationalist debate in general. The acute observation and rigorous analysis of the Traité focused principally not on live human beings but on an imaginatively conceived ideal model. Condillac and his contemporaries did, however, make use of empirical investigation when it was possible. The ideal model itself, as well as other kinds of sensationalist speculation, must have been based on a good deal of largely unrecorded observation of real life, and sometimes there were opportunities for a more scientific, even experimental approach. A case in point was the actual functioning of 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 to distinguish 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 and perfected the operation for the removal of cataracts, the opportunity was created to move it on to a more scientific basis: Cheselden’s observation of a person born blind who was then given sight, reported in Voltaire’s Eléments de la philosophie de Newton, appeared to confirm that the interpretation of visual sensations was not intuitive and had to be learned from experience in conjunction with other sense data. Despite the fragility of its scientific foundations, sensationalist psychology reflected the 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 authority of theology towards (if not quite as far as) science. But there was also an indirect and perhaps more important way in which sensationalist psychology came into conflict with Christianity: it made much easier a totally materialist explanation of man, with the dire moral implications that we shall be examining in the next chapter. The most controversial point in sensationalist analyses of the understanding was the degree to which its operations were produced by an innate active element. If absolutely all mental processes are automatic, as they appear to be in the Traité des Sensations, resulting from pleasureand pain-responses to sense impressions, then the mind is merely an extension of the body: not only is reflexion not an act of the will, but the will itself disappears. But Condillac was primarily a seeker after truth rather than a philosophe, and sought, if anything, to avoid controversy. Others, however, had distinctly more polemical intentions. One of the most unambiguous expositions of the passivity of the understanding and of the 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 been written by Buffon or Condillac (interesting indeed for his perception of their position in the matter). Quesnay argued that willing is merely a form of feeling: ‘to want or to be willing is nothing other than to feel pleasantly; not to want or to be unwilling is similarly nothing other than to feel unpleasantly’. It was this thesis, developed at considerably greater length, which, two years later, served as the starting point of the scandalous De l’esprit, by Claude-Adrien Helvetius (1715–71): not only was the book banned, but the outrage it caused contributed to the definitive banning of the Encyclopédie itself. Helvetius began by arguing that remembering and even judging are merely forms of feeling, though his demonstration is neither very subtle nor very convincing as he deals with various possible objections. The central thesis of De l’esprit was that all minds are potentially equal, since all men (it is not entirely clear whether Helvetius intends this to include women or not) are endowed with the same capacity of attention which can enable them to attain to the most elevated ideas. Helvétius, it may be argued, makes clear the materialism which had been latent in Locke. But sensationalism was not the only road to materialism, and the scientific progress discussed earlier also led a number of thinkers in a similar direction. In particular, despite Newton’s own views, gravitation came to be seen as a property of matter, alongside extent and impenetrability, so that matter was no longer passive, as for Descartes, but capable of moving itself, and this was to provide an obvious basis for materialist explanations of the world. But the first thoroughgoing materialist of the French Enlightenment, subsequently much admired by Marx, was not a physicist but a doctor, 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 the Newtonian 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’âme attempts to destroy the case for the spirituality of the soul, arguing that there is no evidence whatsoever to lead one to suppose that the capacity for feeling belongs to a substance distinct from matter. If movement is an attribute of matter, why should this not also be true of feeling, thought, and will? Observation and experience confirm that the soul is material, says La Mettrie, whereas only metaphysical arguments are offered to support the contrary view. He admits he cannot understand precisely how matter feels and thinks, but points out that it is no easier to understand how it moves by itself, while the notion of an immaterial soul is even more inconceivable. He cites various examples which 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 de l’âme, ch. 10, X, [9.11], 87), and then goes on to argue that the exercise of liberty is similarly determined by sensations, and that the judgement is a passive acquiescence in the truth imposed by ‘the evidence of the sensations’. La Mettrie’s principal point, to which he returns in L’Homme machine, is that the socalled soul, which falls asleep with the body and needs food to continue functioning, is merely a way of talking about certain functions of the body. Man, then, is just another animal. The instinct of animals is a product of their brain and nervous system; man’s more complex behaviour is merely the result of having the most complex brain of all the animals: ‘So that everything comes from the force of instinct alone, and the sovereignty of the soul is merely a figment of the imagination’ (Traité, ch. 11, II, [9.11], 93). The parallel 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 are differences between men and animals: La Mettrie is convinced (wrongly, as we now know) that the only thing preventing monkeys from learning to speak is their inadequate organs. In L’Homme plante (1748), he went one stage further and extended the similarity of organization to all life forms, pointing out that the characteristics of animals, such as respiration 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 conventional Christian position, but of any religious or supernatural explanation of man and the universe, and they were consciously replying to the arguments of their adversaries: when La Mettrie attacked the doctrine of final causes, for example, together with the associated argument that the wonders of the universe provide incontrovertible proof of the existence of God, he was attacking the very foundation of the deism propounded by Voltaire and initially by Diderot, who for their part were explicitly refuting the arguments of the materialists. In fact, though atheist-materialists and deists tended to be equally hostile to Christianity, the thought of both has to be understood in the context of the continual debate 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 it was also because most of what he wrote was in the form of a debate, often expressed as dialogue. It is not always easy, as a consequence, to know with certainty what exactly his ideas were. His writings reveal an endlessly inventive thinker, continually indulging in scientific and philosophical speculation, where the author’s thought is sometimes to be found in the conflicting voices rather than in any single one: he was, in short, more given to raising and discussing difficult questions than to proposing answers. Yet despite the ambiguities of his thought, Diderot’s materialism is historically much more significant than La Mettrie’s. Perhaps because of his somewhat confrontational approach (the title ‘L’homme machine’ was surely intended to be provocative), La Mettrie was generally seen as a rather irresponsible extremist, and remained on the fringe of the philosophic movement. Diderot, in contrast, largely no doubt because of his role as principal editor of the Encyclopédie, was, more than anyone else, right at its centre, one of its acknowledged leaders. He was a friend of many of the most important thinkers of his day, meeting them frequently, 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 of ideas 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 opposing views. 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 the physical world; but immediately afterwards, in response to the deist’s claim that it is as inconceivable that the universe could have come into existence by the chance combination of atoms as that Homer’s Iliad could have been produced by a chance combination of letters, he demonstrates that, taking into account the eternal duration of matter and movement, together with the infinity of possible combinations, it would be inconceivable if matter had not, by pure chance, ordered itself into some ‘admirable arrangements’ ([9.5], 1:136). By the time he wrote the Lettre sur les Aveugles, three years later, he had already begun work on the Encyclopédie, which helped to bring him into contact with the most advanced scientific thought of the age. The apparent uncertainty of the Pensées now seemed clearly to have given way to atheism and materialism. Much of the work is devoted to a discussion of sensationalism, in which Diderot anticipates the techniques of modern psychology by using the aberrant (here the blind) to provide clues to understanding the normal. Like La Mettrie, he emphatically dismisses the idea of a spiritual soul, declaring that a philosopher blind and deaf from birth trying like Descartes to locate the soul would surely place it not in the pineal gland, but at the tips of the fingers, the source of all his knowledge. But the most direct affirmation of Diderot’s materialism 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 the deists. Just as ten years later, in Candide, Voltaire was to quote the harsh evidence of the real world against Leibnizian Optimism, so Diderot here cites the real world against Voltaire’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, he then 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 fit survived. And using this biological process as an analogy, he proceeded to hypothesize about the world we inhabit, no doubt produced by a similar trial and error series of combinations of matter and movement. After the Lettre sur les Aveugles, which led to his imprisonment as the author of an irreligious book, Diderot’s materialist theories were elaborated, mostly speculatively, in his correspondence, in a number of Encyclopédie articles, and in several individual works, particularly the trilogy known as the Rêve de d’Alembert. They do not constitute a complete system, but they do present a corpus of more or less coherent ideas, reflecting consistent attitudes and a steadily growing preoccupation with biology. The problem of the first cause is resolved once and for all by postulating that movement, 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. Like d’Alembert, Diderot emphasized the unity of the universe, which he described in the Encyclopédie article ‘Animal’ as ‘a single, unique machine, in which everything is connected’. This article indeed attempted to give a unified account of all matter, organic and inorganic. Drawing principally on the ideas of Buffon, it nevertheless went considerably further in getting rid of the divisions between man and other animals, between animals and plants—Diderot quoted Trembley’s recent observations on the fresh-water polyp, which did indeed seem to be neither—and even between animate and inanimate matter. The conviction that there are no true divisions between the different categories in nature led Diderot to an idea he flirted with for many years but expressed most explicitly in the Rêve de d’Alembert, namely the hypothesis that ‘sensibilité’, the capacity to feel, is a ‘general property of matter’ ([9.5], 2:116). This is not to say, of course, that all matter actually feels; sensibility is active in animals, and perhaps in plants, but inert, in other words potential, in inanimate matter. The hypothesis is confirmed for Diderot by the ease with which inanimate matter can cross the borderline to become living—the two obvious examples being the development of the egg in the process of generation, and the even more everyday process of eating: The plants feed on earth, and I feed on the plants’ ([9.5], 2:108). The discussion of the active sentience of animate matter, a major issue in the Rêve, is in 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 de Chambaud (1739–1815), the Encyclopédie’s principal contributor in the field of medicine, were busy showing that all living matter is inherently sentient, a property which manifests itself in a variety of ways in the animal body, in reflexes, in the spontaneous contraction of muscles and organs, in the digestion—even in the response to stimuli of a muscle actually removed from the body. But if Diderot welcomed such scientific confirmation of his materialist theories, it still left many questions unanswered. In particular, if the formation of living beings can be explained by the successive accumulation of sentient ‘molecules’, how does the sentience of the component parts become transformed into a corporate consciousness and identity? Diderot suggests as a possible 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 imagines them becoming fused together by their legs, they pass from the state of contiguity to that of 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 on the memory as the crucial factor in converting sensations into thought—though he realized that memory too was a result of physical organization, perhaps, he suggested, a kind of vibrating fibre. At the same time, he recognized the inadequacy of the usual accounts of the transition from physical sensations to thought, of the kind provided by Helvetius. Faced with the problem of explaining how the sensations received by individual organs come to be co-ordinated, he could only suggest the existence of some kind of central function, a ‘common centre’, which registers all the sensations, but which, being endowed with memory, its own special attribute, makes comparisons and provides the sense of continuity and of identity. Once again he resorted to an analogy to illuminate his explanation—though again it is more striking than philosophically enlightening: just as a spider at the centre of its web is immediately aware of the slightest movement in any of its strands, so the ‘common centre’ is informed of the impressions received in any part of 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 the analogy, but it is clear that he believed in the existence of a ‘mind’ separate from the sensations. It is equally clear, though, that thought was for him a totally physiological function, an automatically determined result of sense impressions, however complex the process might be. His own view of man was no doubt more subtle than Helvétius’s, but it was certainly no less materialist and no less determinist, and if he found Helvétius’s demonstration that judgement and will are merely forms of feeling simplistic, he none the less shared his conclusion that freedom was an illusion. The eponymous hero of Diderot’s novel Jacques le fataliste (written during the 1770s), clearly here the author’s mouthpiece, was convinced that all our behaviour is determined by a necessary (if immensely complicated) series of physical causes and effects. So that the will is the result of conditioning, nothing but ‘the last result of everything one has been since birth up to the present moment of existence’ ([9.5], 2:175). As Diderot had explained in 1756 in a letter to the author Landois, ‘the word “freedom” is devoid of meaning; there are no free beings, 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 our experience 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 more subtle than those of some of his contemporaries. Yet they offer some striking similarities with the thought of d’Holbach, which is so lacking in subtlety that at least one modern historian 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’s correspondence bears witness to frequent lively discussions and arguments between them: there seems good reason to suppose both considerable mutual influence, and a greater 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), is more comprehensive and more overt than that of either La Mettrie or Helvetius. He gives an unambiguous (if wordy and repetitive) account of a totally materialist position, an integrated ‘system’ in which all things, matter, the universe, man, society and government, 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 being born. It is composed of matter, which is eternal and eternally and necessarily in movement, behaving according to fixed laws, such as what d’Holbach calls ‘conservation’ (Newton’s inertia), though he recognizes that not all these laws are yet understood. This is something he stresses repeatedly: everything that is and happens, is and happens necessarily, and if we see what appears to be evidence of chance, or still worse, of supernatural forces, it is because we do not understand the true links in the cause-effect chain—d’Holbach invokes the scientific explanations of the miracles and marvels of the past, such as earthquakes and meteors, and looks forward to a time when posterity will unravel still more of the secrets of nature. Animate beings, since they are composed of matter, necessarily follow the same physical laws as the rest of the universe: plants and animals are made up of an aggregation of parts, held together by‘attraction continuelle’. And since the moral is only a different way of considering the physical, man as a moral being, too, is subject to the same rule of necessity and follows the same laws of nature. D’Holbach is careful to point out, however, that when he speaks thus of ‘laws of nature’, it is no more than a convenient way of referring to the ‘essence’ of things, by which he means the necessary result of the properties they possess. It is of the essence of a stone to fall, and similarly, of the 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 ‘a long sequence of necessary and connected movements’ ([9.10], 1:71), caused by his physiology and its interaction with his environment. All the intellectual ‘faculties’ are derived from the faculty of sentience, and d’Holbach’s explanation of sentience is reminiscent of La Mettrie’s: it is ‘a consequence of the essence and properties of animate beings’ 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 inanimate matter such as milk and bread can become animate through the simple process of ingestion, and discusses the possibility that, as ‘some philosophers think’, sentience may be 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 how the brain acts as the co-ordinator of sense data from different parts of the body, at the same time denying that it has any autonomous activity. Even more than Diderot, and recalling rather Helvetius and La Mettrie, he emphasizes the physicality of the so-called soul, demonstrating that thinking and even willing are only forms of feeling, automatic despite all appearances to the contrary. To will is to be disposed to action: thus, ‘the sight of fruit on a tree modifies my brain in such a way that it causes my arm to move to pick the fruit’ ([9.10], 1:115). D’Holbach, however, was just as aware as Diderot of the implications for morality of the denial of human freedom, and it is in truth misleading in both their cases to consider their scientific materialism and determinism separately from their moral and political thought. However great the interest of both these thinkers in science, their principal preoccupations were with man as a moral and social being, and this, rather than on scientific grounds, was why they were hostile to Christianity. Both of them saw Christianity as fundamentally anti-human and therefore as a force for social evil, and their materialist-based atheism was as much a consequence of this hostility as a cause of it. The priorities shared by Diderot and d’Holbach were in fact characteristic of the French Enlightenment in general. The move towards a greater understanding of the universe triggered by the discoveries of Newton, the development of a scientific approach to the understanding of human psychology stemming mainly from Locke, the enormous strides that were being made in the understanding of the animal world due to the work of Buffon and other contemporary naturalists and scientists, all this led to a new and exciting vision of the world, in which authority (especially that of religion) no longer held sway and every territory was available for exploration. But once the old certainties were dethroned, frightening possibilities were laid bare, and to thinkers who were above all anthropocentric in their concerns, it might well seem that there were far more pressing matters to be examined than, for example, the structure of the universe, the differences between animate and inanimate matter, or even the origin of life. It had become essential to re-examine the very fundamentals of human life, the nature of morality and the rules governing human behaviour and social organization, and it is to the discussion of these that the next chapter is principally devoted. BIBLIOGRAPHY Eighteenth-century Works 9.1 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, Garnier Frères, 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, Slatkine Reprints, Geneva, 1973. 9.11 la Mettrie, Julien Offroy de Textes choisis, Les Classiques du peuple, Paris, Editions sociales, 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 University Press, 1937. General Surveys 9.16 Cassirer, E. The Philosophy of the Enlightenment, trans. F.C.A.Koellen and J.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 and Nicolson, 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 Authors 9.21 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 French Enlightenment, 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, 2e edition, 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–.