Céline Spector

.

The Discourse on the Sciences and the Arts was conceived when Rousseau went to visit Diderot, who was then imprisoned in the Donjon de Vincennes because of the scandalous Letter on the Blind. The Letter questioned the idea of intelligent design, and ended with an ironic call for mercy addressed to the God of Clarke and Newton. At that time, both men agreed on the diagnosis that 'civilized' societies are corrupt. Rousseau felt close to the author of the article 'Need' (Besoin), in which Diderot described the artificial needs that make men 'perhaps more unhappy' in society than if they had remained isolated or scattered. The idea of opposing the claim that the sciences and the arts could develop along with liberty or virtue was encouraged by Diderot, who urged his companion to compete for the prize sponsored by the Academy of Dijon, and encouraged him to defend his scandalous claim. The First Discourse was Rousseau's first success in the Republic of Letters. Diderot even took it upon himself to find a publisher for the Discourse, and seemed really glad to see his friend raised to the skies. Despite this, Rousseau will, a few years later, consider that Diderot always tended to make him more satirical than was natural to him (Furbank 1992: 82).

Yet was this truly the case? Rousseau and Diderot fell apart over the idea of natural sociability, which Diderot, against Hobbes, had not renounced. In 1745, Diderot had produced a translation of Shaftesbury's Inquiry concerning Virtue and Merit (1699), which he sprinkled with fifty personal notes. Diderot gave Rousseau a copy on March 16, 1745, and according to Paolo Casini and J. Spink, this pledge of friendship points to the role that certain ideas of Shaftesbury played in their discussions and quarrels of the years 1750-1755. In the dialogue entitled The Moralists, Shaftesbury had rejected the idea that homo homini lupus, as well as the Hobbesian theory of the social pact. In the Inquiry, he mentioned social affections and placed the origin of the desire for society in filial love.

That in the passions and affections of particular creatures there is a relation to the interest of a Species or common Nature (as there is an affection towards the propagation of the kind, towards the nurture of the young, towards mutual support and succor) this is not deniable, neither will it be denied; therefore, that such an affection as this of a creature towards the good of that common nature, is as proper an affection, and as natural to him, as to any member of a body to work in its own way, as to a stomach to digest, as to other entrails to perform their other offices, as to any other part in an animal body to be so affected, and to operate so as is appointed to it in its system. [START_REF] Shaftesbury | Complete Works, Selected Letters and Posthumous Writings[END_REF], II, I, 1: 145-7) Diderot was sensitive to this passage, and added in a footnote: 'One could add to this, that we are, each, within society, what a part is relative to an organized whole,' like the cogs of a watch. To be sure, men are naturally self-interested, but working for one's species does not mean renouncing one's particular interest. It is absurd to believe that in every system of creatures the interest of the individual goes against the common interest. Truly, 'the creature's particular interest is inspearable from the general interest of the species' (Diderot 1975: 361-362). Like Shaftesbury, who in the Inquiry concerning Virtue and Merit, republished in 1711 in the Characteritiks, used either 'interest of a species,' 'social affection,' or 'love of mankind,' Diderot first considered that the common interest is the bond of all societies. He continued the tradition which, from Locke to Shaftesbury, through Pufendorf, Cumberland, and Clarke, refused to reduce mankind to pure egoism. Diderot's theory should not, however, be distorted: in the years that followed, he also relied on Hobbes to counteract a naive view of natural sociability. The article 'Greeks (Philosophy of)' states that men without conventions or leaders, endowed only with a few vague notions of the just and the unjust, would be restrained only by the fear of reprisals, which is by itself insufficient to prevent crimes (Encyclopédie,VIII,908).

If something such as a social instinct exists, however, it must be cultivated. In the Letter to Landois of June 29, 1756, in which he rejects the illusion of freedom, and with it the idea of virtue or vice, Diderot argues that the evildoer is doomed to be destroyed. Diderot thus held to a middle path: while he accepted the Hobbesian or Spinozist critique of free will, he also hoped to retain the idea of a natural germ of sociability, which he argued needed to be educated, as well as supplemented by the fear of laws. In 1765, the article 'Hobbism,' which was published in Volume VIII of the Encyclopedia and largely inspired by Brucker, sketched a third way between the assumptions of the natural wickedness and of the natural goodness of man, embodied respectively by Hobbes and Rousseau:

The philosophy of Monsieur Rousseau of Geneva is almost the inverse of that of Hobbes. The one thinks man naturally good, and the other thinks him wicked. For the philosopher of Geneva the state of nature is a state of peace; for the philosopher of Malmesbury it is a state of war. If you follow Hobbes, you are convinced that laws and the formation of society have made men better, while if you follow monsieur Rousseau, you believe instead that they have depraved him (…) Both men were extreme. (Diderot 1992: 27-28) This criticism of Rousseau, however, was preceded by that which Rousseau had addressed to Diderot, for the Second Discourse demonstrated that all the versions of natural sociability were equally ingenuous. This disagreement increased as Rousseau, over the years, moved away from the Philosophes.

The Discourse on Political Economy

Despite their different approach to opera during the Querelle des Bouffons (1752) as Rousseau argued forcefully against French music, the collaboration between Rousseau and Diderot was very close when Rousseau contributed by the article 'Economy' to Volume Five of the Encyclopedia (Wokler 1975, 55-111). Diderot and d'Alembert had invited their friend to write the articles on music, but Rousseau also contributed with his major article on morals and politics. Having read the article 'Natural Right' by Diderot, Rousseau inserted into his article 'Economy,' the concept of the 'general will,' which he now used to replace that of the 'collective will' (Bernardi 2006, 309-354). Rousseau had been struck by the concept of 'general will,' which had been introduced by Diderot in the form of the 'general will of the human race' (volonté générale du genre humain). This led Rousseau to conceive the preamble and the first part of his article as a specification of this concept, which Montesquieu had only mentioned once in The Spirit of the Laws (XI, 6;Riley 1986: chap. 5).

How did Rousseau reinterpret the concept of the general will? The article 'Natural Right' suggested-in contrast to 'Right of Nature' by Boucher d'Argis, Burlamaqui's mouthpieceto conceive natural law in a non-metaphysical way, and thereby to 'save' it against massive objections. Diderot thus discussed natural law in terms of the living reality of the species. Natural law is no longer a law obeyed by the will. Rather, it is a norm of reciprocity which is accessible to reason as the individua experiences his insertion within his own species. The human race is the only tribunal to which disputes concerning the nature of the just and the unjust are to be brought, for the 'good of all' is the only passion the individual feels as part of his species. Diderot then introduced the concept of the 'general will,' the source of justice, which he now substituted for the golden rule of modern natural law (do not do to others what you would not want them to do to you). He who follows his particular will tends to become the enemy of mankind, for the general will expresses everyone's desire to watch over the preservation and happiness of the whole species. Diderot probably relied here on Bayle and Barbeyrac, who argued that the object of sociability is 'what men are entitled to demand from each other' [START_REF] Postigliola | De Malebranche à Rousseau : les apories de la volonté générale et la revanche du raisonneur violent[END_REF]Larrère 1992: chap. 1, 51-57). For Diderot, the general will defines moral duties on a purely horizontal level, that of reciprocal rights and duties. Political obligation is of the same nature as social and moral obligation: the general will is the rule of conduct of an individual toward the society of which he is a member, and of the society of which he is a member toward other societies. From this standpoint, the general will, which 'never fails' and serves to justify justice, humanity, and virtue, is related to sociability, understood as a mutual obligation between equals.

Objecting to Diderot's view, Rousseau in his article 'Economy' traces the origin of political obligation to the social contract. Unlike his former friend, who conceived of the general will as 'deposited' in the principles of the prescribed laws of all civilized nations, or in the social practices of 'savage and barbarous peoples,' as well as in the tacit conventions of the 'enemies of the human race,' Rousseau conceived of the general will only at the level of the state. The reciprocal duties of equals are not associated to what we owe to the 'human race' but rather to what we owe to the political body under the aegis of the 'general will.' Although Rousseau draws upon the article 'Natural Right' by quoting the classical reference to thieves who, enemies of virtue in the great society, adore its simulacrum in their caves (the fragment seems to have been added to the first draft and the reference to the article 'Rightt' did not appear in the first version of the manuscript), he rejects Diderot's claims: to him, the 'great and luminous principle' of the general will borrowed from the article 'Right' is ill-conceived. For, in his view, the feeling of humanity evaporates and weakens as it extends over all the earth, such that it is necessary to bind and compress mutual interest and compassion to make them active. On the scale of political bodies, the people is the only sovereign and the only legitimate source of justice. The rules of justice can only be valid for fellow citizens, and not for humanity as a whole. In Rousseau's account, the general will is not universal; it must be grounded on the constitution of a true 'common self' (moi commun).

The Geneva Manuscript

In the following three years (1755-1758), the former best friends gradually became enemies for major ethical and political reasons [START_REF] Citton | Retour sur la misérable querelle Rousseau-Diderot. Position, conséquence, spectacle et sphère publique[END_REF]. On a personal level, Rousseau had already irritated Diderot by refusing the royal pension awarded him after the courtly success of the Devin du Village in 1753. Rousseau had forcefully asserted his taste for independence, which would only increase after his reform. Determined to live what he preached, he gave up his whig and left Parisian society (Confessions VIII, CW 5,). Rousseau's retreat at Montmorency could only appear to Diderot as a desertion. On his account, the new Diogenes had betrayed the intellectual role he was intended to play in the Enlightenment republic of letters and backstabbed the Philosophes (Shea 2010, 102). On May 10, 1757, he wrote him 'Adieu le citoyen. Yet a hermit is a very bizarre citizen.' When Rousseau received the play Le Fils naturel, he felt that he was the target of Diderot's words: 'il n'y a que le méchant qui soit seul' (only the wicked man lives alone) and found the remark highly offensive. In Book IX of the Confessions, Rousseau's writes that his infatuation for Sophie d'Houdetot, Louise d'Epinay's sister-in-law and the mistress of their common friend Saint Lambert, further envenomed their relations. Rousseau confided to Diderot the secret of his passion, but Diderot, falsely believing that Rousseau had confessed to Saint Lambert as he had advised him, openly spoke about Rousseau's feelings to his friend. Rousseau thought himself betrayed. The quarrel became even worse when Madame d'Epinay, who was ill, planned a journey to Geneva, and Rousseau refused to accompany her in spite of Diderot's request that he do so. Finally, the rupture was consummated, as evidenced in the Letter to d'Alembert on the Theater 'I had an Aristarchus, severe and judicious. I have him no longer, I no longer wish to have him; but I shall regret him always, and he is missing much more from my heart than from my writings' (March 20, 1758, CW 10, 255). On March 2, Rousseau had written his last letter to his former friend, which would remain unanswered. In the same year Diderot set down on paper the list of his grievances against Rousseau and the events causing the break, which would be published in the Correspondance littéraire of 1795. In June 1759, Diderot wrote to his mistress Sophie Volland about the Letter to d'Alembert: 'This, my tender and solid friend, is the work of the great sophist' (Furbank 1992: 148-164;[START_REF] Cammagre | Rousseau 'grand sophiste'. Enjeux et significations d'une accusation de la correspondance de Diderot[END_REF].

On a theoretical level, Diderot became Rousseau's main target in Chapter Two of Book One of the Geneva Manuscript. The distance between their views was set out in a chapter entitled 'On the general society of the human race,' after Rousseau struck out the original title ('That there is naturally no general society among men'). Whereas Diderot sought to naturalize the theory of social instinct developed by Shaftesbury, Rousseau actually returned to Hobbes. For Rousseau, the absence of a natural society of the human race condemned Diderot's theory to inconsistency, for voluntary association between men could not emerge from a spontaneous association based on sociability. Following upon the Second Discourse, the Geneva Manuscript first dismissed the classical argument of modern natural law, which invoked the natural weakness of man in his primitive state to explain the appearance of society. Rousseau rejected the idea that human beings are naturally vulnerable: only the transition to civil society broke the primitive proportion between force and needs; once that proportion was broken, artificial wants and rivalry arose, which introduced conflict.

Rousseau confronted modern natural law with its own contradictions. In the Geneva Manuscript, the social bond of interest does not give rise to a willingness to cooperate: our needs bring us closer as our passions divide us. For the individual to be satisfied, he must enslave and enslave others. Rousseau's refutation of the idea of a general society of the human race thus takes place in two stages: in the first, he rejects the hypothesis of a natural feeling of humanity or of universal benevolence. In the second, he objects to rational sociability, and to social cooperation naturally grounded on reciprocity. Rousseau dismissed the path of feeling (for each one always desires to profit from the benevolence of others without submitting himself to a reciprocal obligation), as much as the path of reason (for it is always rational to prefer one's own advantage and to try to fool or dominate others).

This conclusion sounds like a synthesis of the Second Discourse: civil society cannot emerge from a spontaneous development that reconciles justice and interest. What does justice require? That natural inequality be compensated, at least for the survival of the weak, a sine qua non precondition for the existence of a 'society.' But this is not the case: the society of needs gives new strength only to the one who already have too much strength, 'whereas the weak manlost, stifled, crushed in the multitude-finds no place of refuge, no source of support for his weakness, and finally perishes as a victim of the deceptive union from which he expected happiness' (GM, 77). The unity of the human race does not exist. There is a real division between the poor and the rich, who can give themselves supplementary forces by using others to satisfy their needs.

Rousseau's adversary here could be the Diderot of the Suite de l'apologie de l'Abbé de Prades (Proust 1995: 393-396). There, the author argued that, despite men's instinct (which leads to the 'flock' called society), the origin of social relations is violent because of men's unbridled passions. From then on, the weak are the victims of the strongest, the strongest are in their turn immolated by the weak, and soon the inequality of talents destroys between men the bonds that their own utility and their external resemblance had suggested to them for their reciprocal preservation (Diderot 1994: 538).

Diderot justified the necessity of conventions to prevent men from devouring each other like ferocious beasts: laws must compensate for the disadvantages of original anarchy and help men reach the stage of 'polite society.' Diderot thus took into account Hobbes' critique of Aristotelian sociability. Rousseau answered Diderot, however, by radicalizing Hobbes's claim: if the strong always prevail, conventions cannot be established without damage to the weak, since they are built upon already existing social relations. Primitive social life is not peaceful cooperation: without a sufficient and perennial intersection of interests, social life necessarily leads to injustice and violence. Incapable of hearing 'nature's gentle voice,' humanity will never taste again the innocence of a lost paradise.

The 'violent reasoner' But Rousseau's refutation does not end there: he analyses, and therefore dissolves, the concept of human race that Diderot had made the true subject of natural law. The polemic is even more frontal here: for Rousseau, the human race is a 'collection' of individuals and not a substantial entity. It is not a substratum associated with the spirituality of the soul (which Diderot not only granted, but argued himself); nor is it an instance with respect to which we have duties (which Diderot denied). There is therefore no 'scientific,' non-metaphysical, ground for natural law. The Geneva Manuscript dismisses Diderot's arguments as mere mystification. There is no such thing as a 'general will' capable of prescribing to all men the norms of justice, that of their reciprocal duties. For what would be this 'individual' constituted by the species, which is itself only the collection of particular individuals? Rousseau argues by reducing Diderot's argument to an absurdity: let us admit that the 'human race' is not a real entity, that is, not a physical person, but rather a 'moral person.' Then for this moral person to be endowed with one and the same will, it would be necessary that it really unites the particular wishes of each of its members. The human race would at least need, if not a common will resulting from a mechanism of authorization as in Hobbes, a 'common sensibility' (a sensorium commune). Now, if it makes sense to say that a common sensibility could exist in a collective being, it could do so only in a collective body already bound by a sense of belonging, by a 'common self' (moi commun). In the Geneva Manuscript Rousseau thereby denounces the impotent or chimeric nature of natural law. He emphasizes the paradox: either natural law is impossible to know (in the pure state of nature), or it has no motivational force to ground it. Natural law as 'law of reason' is accessible to man only when he is no longer able to apply it, because of the development of his asocial passions.

Rousseau's remaining criticism is directed against the Diderotian concept of the general will. In the article 'Natural Right,' Diderot had put on the stage a 'violent reasoner.' This reasoner, a passionate being, was so tormented by his destructive passions that he who would not want to live if he could not satisfy them. But he was not, according to Diderot, a moral monster. He was rational and even fair, by proposing to other men his own life in exchange for theirs: 'I realize that I bring terror and confusion to the human race; but I must either be miserable, or create misery for others, and no one is more dear to me than myself. Let no one blame me for this abominable predilection; it is not a matter of free choice. It is the voice of nature, which never speaks more forcefully within me than when it speaks in my favour' (…) 'Yet I am fair and honest,' he will continue. 'If my happiness demands that I rid myself of all persons who intrude upon my life, then anyone else may equally rid himself of my presence if it offends him.' (Diderot 1992: 18) As has often been noted, the violent reasoner served to encamp the Hobbesian individual in the state of nature, by proving the impossibility of an individualistic definition of natural law. For Diderot, no one would be able to convince the violent reasoner to subordinate his passions to the idea of justice. No one could convince him that he should renounce his desire to harm. The only recourse would be to stifle or strangle him for the greater good of society. Effective justice cannot be defined at the level of the individual: hence the appeal to the species and to the will of the member as part of the whole-the general will. Now in the Geneva Manuscript, Rousseau again summoned the violent reasoner. Under the name of an 'independent man' or 'violent reasoner,' he offers a different discourse, a purely Hobbesian discourse which denounces the absence of any guarantees of reciprocity. Everyone wages war so long as he does not have the guarantees of peace; each pursues his narrow interest so long as he is not certain that others don't do the same; and so on. It is Rousseau who here wants to be the most Hobbesian of the two: 'I would try in vain,' he might add, 'to reconcile my interest with that of another man. Everything you tell me about the advantages of the social law would be fine if while I were scrupulously observing it towards others, I were sure that all of them would observe it toward me. But what assurance of this can you give me, and could there be a worse situation for me than to be exposed to all the ills that stronger men would want to cause me without my daring to make up for it against the weak? Either give me guarantees against all unjust undertakings or do not expect me to refrain from them in turn.' (Rousseau 1978: 160) As usual, Rousseau refers his opponent to his own principles. Diderot believed that the only problem raised by the 'violent reasoner' was his excessively passionate temperament. But Rousseau shows that even if he were more measured in his desires (simply concerned with his 'independence' and his own preservation), he would nonetheless resist the obligation to submit to rules of sociability. If he really wants to reason, the independent and enlightened man ('l'homme éclairé et indépendant') will have to admit that he can only enjoy his rights if he accepts his duties, and therefore he will enjoy nothing at all in the absence of an external guarantor of moral obligation. Justice therefore has no chance of imposing itself spontaneously, by the sole force of reasoning. The relevance of this point is illustrated by the logic that governs international relations-an argument already mentioned by Hobbes to establish an analogy between the state of nature and the state of society in the absence of political sovereignty. Nature does not rationally command justice.

Rousseau pushes Diderot up against the wall: if one follows his project, which is to dissociate morality and religion, it is still necessary to find a genuine basis for moral and political obligation. To be sure, Rousseau's irony and sarcasm were first directed at Burlamaqui and Boucher d'Argis, who, unlike Pufendorf, gave a religious foundation to sociability and obligation. Yet the criticism also reaches the 'philosopher,' who is not as realistic as one might have thought. Cosmopolitanism is meaningless in the natural state of mankind:

But the philosopher will send me back to the human race itself, which alone ought to decide because the greatest good of all is the only passion it has. He will tell me that the individual should address himself to the general will in order to find out to what extent he should be man, Citizen, Subject, father, child, and when it is suitable for him to live and to die. 'I admit that I see in this the rule than I can consult, but I do not yet see,' our independent man will say, 'the reason for subjecting myself to this rule. It is not a matter of teaching me what justice is, but of showing me what interest I have in being just.' Indeed, no one will deny that the general will is a pure act of the understanding, which reasons in the silence of the passions about what man can demand of his fellow man and what his fellow man has the right to demand of him. But where is the man who can be so objective about himself; and if concern for his self-preservation is nature's first precept, can he be forced to look in this manner at the species in general in order to impose on himself duties whose connection with his particular constitution is not evident to him? Don't the preceding objections still exist and doesn't it still remain to be seen how his personal interest requires his submission to the general will? (GM, 80) Rousseau ironically refers Diderot to his own principle, the one the latter opposed to the modern advocates of natural law, in particular to Boucher d'Argis and Burlamaqui: natural law is not divine law, even if it were accessible to reason alone. It is not a law whose binding force comes from the submission of man to his Creator. If we follow Diderot, natural law must then be its own motivation. But then, what would actually motivate us in such a law, and how would this law inhibit desire, since we know that the human race, as an abstract idea, has no effect on the agent? For mankind is a moral person, which naturally cannot oblige us. The argument that there exists a social instinct is therefore deconstructed. For Rousseau, Diderot is fully part of the tradition of natural law. He has not really broken with it (Radica 2008: 129-149;[START_REF] Spector | De Diderot à Rousseau: la double crise du droit naturel moderne[END_REF].

Is this a genuine refutation or a mere polemic stance? If Rousseau had been able to read the article 'Greeks (Philosophy of the),' published later in 1765 in Volume VIII of the Encyclopedia, he could not have accused Diderot of having ignored the importance of laws in stabilizing the social order. Sticking to the article 'Natural Right allowed Rousseau to take on the beautiful role: he undoubtedly simplifies Diderot's thought in order better to challenge it. Yet Rousseau succeeded in extracting from Diderot's unstable thought a founding principle, that of the general will, an infallible source of the norms of justice-a principle which he fully made his own in the Social Contract.

Materialism as a fraud

Finally, Rousseau takes Diderot as his main target in the Profession of Faith of the Savoyard Vicar, where materialist philosophy is considered as blind and deaf-probably an ironic reference to Diderot's own letters: 'The more I reflect on thought and on the nature of the human mind, the more I find that the reasoning of materialists resembles that of this deaf man. They are indeed deaf to the inner voice crying out to them in a tone difficult not to recognize. A machine does not think; there is neither motion nor figure which produces reflection' (Rousseau 1979: 280). In Book Four of Emile, the Vicar first infers from experience that movement is not essential to matter, calling for a foreign cause. His mind refuses to approve the idea of selfmoving matter: he is forcefully persuaded that the natural state of matter is to be at rest, for unorganised matter cannot move itself or produce any action. Against Diderot and the other 'philosophers,' the Vicar also stresses that the world cannot be conceived as a 'large animal.' Hence the necessity of a first engine, and the 'first dogma or article of faith,' which establishes a will that moves the universe and animates nature (Rousseau 1979: 576).

In his Pensées philosophiques, his first original book published in 1745, Diderot was still a deist and provided some arguments against atheism-which did not prevent the Parliament of Paris from condemning the book to be burned in public [START_REF] Duflo | Diderot philosophe[END_REF]. In particular, he shared the difficulties encountered by materialism in accounting for the order of nature attested by the invention of the microscope: It is not from the metaphysician that atheism has received its most vital attack. The sublime meditations of Malebranche and Descartes were less calculated to shake materialism than a single observation of Malpighi's. If this dangerous hypothesis is tottering at the present day, it is to experimental physics that the result is due. It is in the works of Newton, of Musschebroek, of Hartsoeker, and of Nieuwentyt, that satisfactory proofs have been found of the existence of a reign of sovereign intelligence. (Diderot 1916, §18: 34-35) Diderot thus distinguished the sceptical or atheist approach from the deist approach. In the Pensées philosophiques Diderot staged a dialogue with an atheist on the existence of God, the reality of good and evil, and the immortality of the soul. Now, the atheist disagrees with the idea that the human mind is unable to understand the emergence of life and intelligence. To him, this argument does not convincingly demonstrate the existence of God: I open the pages of a celebrated professor, and I read: 'Atheist, I concede to you that movement is essential to matter; what conclusion do you draw from that? That the world is the result of a fortuitous concourse of atoms? You might as well tell me that Homer's Illiad or Voltaire's Henriad is the result of a fortuitous concourse of written characters.' I should be very sorry to use that argument to an atheist; he would make quick work of the comparison. (Diderot 1916: 38) In Rousseau's letter to Voltaire on Providence, Rousseau mentions this passage:

I remember that what has struck me the most forcefully in my whole life, on the fortuitous arrangement of the universe, is the twenty-first philosophical thought, where is shown by the laws of analysis of chance that when the quantity of the throws is infinite, the difficulty of the event is more than sufficiently compensated by the multiplicity of the throws, and that consequently the mind ought to be more astonished by the hypothetical continuation of chaos than by the real birth of the universe. (LV,(117)(118) For Rousseau, this atheistic argument is clearly made in bad faith, and nothing could make him change his mind on this fundamental issue. Against philosophers who reject the proof of the existence of God which comes from inner feeling as long as it cannot be made into a rational argument, Rousseau maintains that it would be inhumane to disturb peaceful souls.

Rousseau thus dismisses the materialist philosophers (not only Diderot, who was not a deist any more, but also Helvetius, whose provocative book De l'esprit Rousseau had read between the draft of the Manuscrit Favre of Emile and the later versions of the manuscript). Certainly, the infinity of throws deployed in a supposedly infinite time compensates for the difficulty of producing the current order of the universe. But this argument speaks only to reason. It convinces without persuading. In the Profession of Faith, the Savoyard Vicar thus turns scepticism against itself: it is precisely because our mind is confused and lost in the infinity of relations which compose the harmony of the world that it is impossible to exclude an intelligent design, a first intention, or a 'unity of purpose.' Rousseau describes as absurd the refusal to recognize an organizing intelligence: 'let us listen to our inner sentiment. What healthy mind can turn aside its testimony; to which unprejudiced eyes the sensible order not proclaim a supreme intelligence; and how many sophisms must be piled up before it is impossible to recognize the harmony of the beings and the admirable concurrences of each piece in the preservation of the others? They can talk to me all they want about combination and chance. Of what use is it to you to reduce me to silence if you cannot lead me to persuasion…' (Rousseau 1979: 275). Materialism is not an error. Rather, it is a fraud. * Finally, Rousseau also disagreed with Diderot and his friends of the d'Holbach coterie on the existence of the soul and of free will. Surely, freedom of the will is no better known than the activity of the understanding. But again, Rousseau reverses the burden of proof: 'It is not the word freedom which means nothing; it is the word necessity.' This is the meaning of the third article of faith that combines the belief in freedom and the belief in the spirituality of the soul: 'Man is therefore free in his actions and as such is animated by an immaterial substance. This is my third article of faith' (Rousseau 1979: 280-281).

Rousseau's thought was first constructed on the ground of his debt to Diderot, from whose thought he borrowed not only his first critique of civilization, but also the concept of the 'general will.' But with his own genius, he immediately distanced himself from Diderot, since the general will can only be conceived among fellow citizens, who are bound by a feeling of belonging to the same political body. The disagreements between them grew to the point of rupture at the very moment when Diderot accused the hermit of Montmorency of gross ingratitude toward his protector, Madame d'Epinay. In the Social Contract, Rousseau went so far as to erase all trace of debt and controversy with regard to Diderot: his desire to make his former mentor disappear is probably part of the reason which led him to abandon Chapter Two of Book One of the Geneva Manuscript and to construct his own system -the 'principles of political right.'

The rest of the story is well known: convinced that Diderot (with Grimm) was the architect of a conspiracy that aimed to discredit him in Paris and throughout Europe, Rousseau reread the history of their intellectual friendship, arguing that Diderot insinuated into his first writings the blackness and the sarcasms to be found there in order to make him odious to public opinion. For his part, Diderot did not cease to manifest his bitterness. In a letter to Falconet dated September 6, 1768, he affirmed himself resolved never to enter into a public quarrel against his old friend. But this good intention did not last. Rousseau accused the philosophical party of hypocrisy and servility. His testimony in the Confessions was a slander against his friends and against the enterprise of justice and emancipation to which Diderot devoted his life. Accused of having betrayed the cause of the philosophers while they were in the height of danger, Rousseau was then ridiculed as a false censor of arts and letters who was only eager for fame and glory. After all, the portrait of Quentin de Latour exposed in the Salon of the Louvre in 1753 made him appear not like an Epictetus, but rather 'well dressed, well groomed, well powdered, ridiculously seated on a cane-backed chair' (Diderot 2009: 210). Contributing in 1770 to the Histoire de Madame de Montbrillant written by Madame d'Epinay, Diderot distorted the facts and darkened Rousseau's reputation-yet the text was not published at the time (Fabre 1975: 52-56). But the worst was to come: in his Essay on the Reign of Claude and Nero, Diderot issued a pro domo plea against Rousseau: whereas the first edition took its precautions against the possible publication of the Confessions, the second introduced a critique of his paranoia and ingratitude. Published in 1778, the year of Rousseau's death, the recrimination was interpreted as a seizure of 'violent delirium;' and to answer this objection, Diderot in the 1782 version of the essay devoted seven subchapters to even harsher criticism, this time referring to his former friend by name (Fellows 1977: 165). According to him, the pseudo-friend of truth was a profound hypocrite; the coherent philosopher who pretended to live rigorously according to his moral standards was nothing but a coward, a moral monster, a 'deceitful villain' who wrote with the Confessions an 'vile libel,' full of pride, hatred, contradiction, and perfidious eloquence: 'This Jean-Jacques that you see was a pervert' (Diderot 1994(Diderot : 1029-36;-36;Citton 2004: 70-77;Salaün 2006: 9-18, 131-139). Yet while blaming the philosopher who became in the woods an 'anti-philosopher,' Diderot also finally came closer to certain ideas of his brotherly enemy: 'and if Jean-Jacques was right?'

This article considers that Rousseau, when he still was a friend of with Diderot until around 1754 was quite close to an atheistic thought. It also wonders whether Diderot's play Le Neveu de Rameau does not implicitely give a voice toRousseau.

A few years later, he returned to his stand as a man of letters complaining of worldly solicitations, and vindicated in his own way the Cynic Diogenes (Lilti 2005: 205-207; Shea 2010: 47-56). After all, Rousseau may have been right to flee the servitudes of courtly and urban life. When Diderot quarrelled with Grimm in his Lettre apologétique de l'abbé Raynal à M. Grimm, he rehabilitated Rousseau: at least he was true to his principles, even though he was lying. Socrates and Diogenes rather than Aristippus? Laughs best who laughs last…

Larrère, C. (1992) L'Invention de l'économie au XVIII e siècle. Paris: PUF, pp. 51-57.

In this general book about the invention of political economy, the author devotes the first chapter to the issue of natural law and includes a study of Diderot's article "Natural right" in the Encyclopédie.


Céline Spector

The "Lights" before the Enlightenment: The Tribunal of Reason and Public Opinion 1

The appearance of the phrase "the century of lights" (siècle des lumières) has been a subject of a number of recent studies. 2 The work of Roland Mortier has been particularly helpful in paving the way for new avenues of research: Mortier has argued that the appearance of the plural form of the metaphor "the lights" (les lumières) in France can be dated back to the seventeenth century. 3 Considered in a religious context, the metaphor of light was transposed onto the secular terrain of the "natural light" thanks to René Descartes and his disciples. My goal in this essay is to determine the moment at which the idea of a "century of lights" first appeared. The novelist and historian Charles Sorel denounced the tendency of his age to define itself with reference to enlightenment as early as 1671: "This century is well enlightened, for one hardly hears of anything but lights. One puts this word everywhere in place of where one used to use 'mind' or 'intelligence'; and it often happens that those who use this word apply it so badly, that one might say they see nothing at all with all of their lights." 4 In the April 1684 issue of the Nouvelles de la République des Lettres, Pierre Bayle proclaimed himself to be in favor of a rigorous method in historical research that would allow his century to be properly praised: "Will it be said […] that we have abandoned the honor of this century to the ridicule of those of who came after us? […] One prides oneself of being extremely enlightened in this century: and yet, perhaps one has never had more audacity to make up fables." 5 Consequently, it seems tempting to oppose the lights (of autonomous reason) to the darkness (ténèbres) of prejudice, to the reliance on traditional authorities, and to the barbarism of fanaticism and superstition. In 1732, Bernard Le Bovier de Fontenelle, the perpetual secretary of the

Académie des sciences, illustrated this combative attitude in expressing his desire to disperse the darkness that posed an obstacle to the expression of the truth: "For some time, an almost entirely new philosophical spirit [esprit philosophique] has spread all over, [it is] a light that hardly enlightened our ancestors." 6 In discussing the merits of Antoine Houdar de La Motte's literary works, Fontenelle took up the defense of his modern party and criticized the Ancients, whom one now only read "out of duty" and no longer "for pleasure," as was the case with the Moderns. As Roland Mortier has noted, a number of Enlightenment thinkers, including Montesquieu, Turgot, Voltaire, and the Encyclopédistes followed Fontenelle's lead in praising the Moderns and extolling the literary and philosophical achievements of their century. In the Encyclopédie article "Gens de Lettres," Voltaire proclaimed the following with enthusiasm:

Previously, in the sixteenth century, and well before the seventeenth, literary scholars spent a lot time on grammatical criticism of Greek and Latin authors; and it is to their labors that we owe the dictionaries, the accurate editions, the commentaries on the masterpieces of antiquity; today this criticism is less necessary, and the philosophical spirit has succeeded it. It is this philosophical spirit that seems to constitute the character of men of letters; and when it is combined with good taste, it forms an accomplished literary scholar. One of the great advantages of our century, is the number of educated men who [can] pass from the thorns of Mathematics to the flowers of Poetry, and who [are able to] judge equally well a book of Metaphysics and a theatrical play: the spirit of the century has rendered them for the most part as suitable for society as for [solitary] scholarship; and this is what makes them superior to those of previous centuries.7

In the "Tableau de l'esprit humain au milieu du XVIII e siècle" that opens his Essai sur les élémens de philosophie (1759), the co-editor of the Encyclopédie Jean-Baptiste le Rond D'Alembert similarly maintained that "Every century that thinks well or thinks poorly, provided that it believes that it thinks and that it thinks differently from the century that preceded it, adorns itself with the title of philosophical; […] Our century has thus called itself supremely the century of philosophy."8 By contrast, Jean-Jacques Rousseau diagnosed the mutations of his century in a way that deplored the vanity of his contemporaries: "We live in a climate and a century of philosophy and of reason. The lights of all the sciences seem to come together at the same time to enlighten our eyes and to guide is in this obscure labyrinth of human life. The greatest geniuses of all the ages bring together their lessons to teach us, immense libraries are open to the public, from infancy a multitude of colleges and universities offer us the experience and meditation of 4000 years […] And have we become better or wiser from this?"9

This essay aims to locate the emergence of a consciousness of the age in the eighteenth century-a consciousness that preceded the development of the formal discipline of the philosophy of history. How can we understand that birth of a historical consciousness that would allow Immanuel Kant to theorize about the Enlightenment not only according to its motto ("dare to know" [sapere aude], have the courage to use your own understanding" and liberate yourself from religious and political tutelage) but also according to its self-reflexivity-the ability, for the first time, to think of the present that is one's own and that truly makes up an epoch? Michel Foucault's interpretation evokes the essential element here, in so far as he less interested in discovering the origin of the word than in understanding what enabled a change of perspective by virtue of which the century itself became the object of its own interrogation and evaluation. 10 This essay thus aims to make sense of the transition from "lights" to "the Enlightenment" (des lumières aux Lumières) and to understand how the term "century of lights" came to designate an era with unstable boundaries. This question does not only concern a verbal transformation and the appearance of a new phrase: the historical investigation would remain incomplete unless one poses the question about the conditions that enabled the invention the Enlightenment as self-reflexive category. The origins and nature of a consciousness that allowed a century to think of itself as "a century of thought" need to be analyzed. Without resorting to social and cultural history that have recently seen major works on this question, I will focus on the history of philosophy. 11 I wish to advance the following hypothesis: the phrase "century of lights" appeared at the precise moment of the constitution of the "tribunal of public opinion"-a tribunal that was dedicated to judging intellectual accomplishments and evaluating their progress over time. Giuseppe Ricuperati has already established the role of literary history in the emergence of periodization and in the appearance of the self-reflexive category of the Enlightenment. 12 Likewise, Diego Venturino has shown the importance of the historical paintings after the French Revolution. 13 However, reflections about the appropriate means of judging artistic and literary works and about the proper tribunal for evaluating the merit of intellectual accomplishments appeared well before the Revolution. In this essay, I argue that that the constitution of the tribunal of public opinion was the prerequisite condition for the emergence of the Enlightenment as a historiographical concept. The Quarrel of the Ancients and the Moderns played a decisive role in this process. Without revisiting the controversy surrounding the interpretations of the Quarrel (whether it was a culture war, a simple polemical contest in which the Ancients were assigned the role of conservatives, and where the Moderns where the most fervent supporters of Louis XIV's absolutist regime and even of 10 Michel Foucault, "Qu'est-ce que les Lumières?, " in Dits et Ecrits (Paris: Gallimard, 2001), v.2, 1381-1397. 11 One must not, of course, exclude references such as one that appears d'Alembert's Essai sur la société des gens de lettres et des grands, where the Enlightenment is described as a social phenomenon, whereby a man of letters operates under the patronage of the state and of the aristocracy. For more, see Hans U. Gumbrecht, "Who were the philosophes?", in Making Sense in Life and Literature (Minneapolis: University of Minnesota Press, 1992), 133-177 and Daniel Brewer, The Enlightenment Past. Reconstructing eighteenth-century French thought (Cambridge: Cambridge University Press, 2008). 12 Giuseppe Ricuperati, "Le categorie di periodizzazione e il Settecento. Per una introduzione storiografica," Studi settecenteschi 14, (1994): 9-106. 13 Diego Venturino, "L'historiographie révolutionnaire française et les Lumières, de Paul Buchez à Albert Sorel," and Diego Venturino, "Appendice sur la genèse de l'expression 'siècle des lumières' (XVIII e -XX e siècles)," both in Historiographie et Usages des Lumières, ed. Giuseppe Ricuperati (Berlin: Berlin Verlaag, 2002), 21-58 and 59-83. ethnocentrism), I hope to locate the origins of historicism in these debates. 14 The emergence of a historical consciousness took place at a moment when the contest between the Ancients and Moderns was at its most heated point, and when each side tried to mobilize the best arguments in favor of or against the superiority of their present age in the domains of science, politics, ethics, and aesthetics. Having brought attention to the "century of Louis the Great," Charles Perrault, the leader of the Modern party, developed the tendency of using this concept with reference to historical periodization, and he forced the Ancients, led by Nicolas Boileau-Dsepréaux, to define themselves in response. 15 Consequently, the following paradox emerged: the transition from "lights" to the "Enlightenment" is not only the product of the militant arguments marshalled by the partisans of the Moderns, but it is also a result of the claims of the supporters of the Ancients, who were critical of the notion of the progress of the philosophical spirit. From Hillaire-Bernard de Longepierre to Jean-Baptiste Dubos, we will thus find a singular gallery of portraits that will reshape our traditional view of the Enlightenment.16

I. The Tribunal of Reason vs. The Tribunal of Public Opinion

It has not been sufficiently noted that the origin of historiographical categorization derived from a conceptual displacement: at first, it was the mind that was described as "enlightened" or "philosophical"; it was the mind that received light, whether divine or natural; it was the mind that enlightened itself by fighting against the blindness of prejudice or the darkness of ignorance and superstition. How did it come to be, then, that it was no longer the mind, but rather the century that became qualified as "philosophical," "enlightened," or "of lights"?

Without a doubt, it is necessary to explain the factors that gave rise to the "charts of the progress of the human mind" in the emergence of the history of philosophy. In fact, what is often attributed to d'Alembert, Voltaire, or Turgot had earlier roots: from the end of the seventeenth century, Cartesianism and empiricism brought about debates about the origins of ideas and the genealogy of human knowledge, about the training of the mind at the individual, societal, and universal level. It is in this context that it became suitable to think about the progress of the human mind, about the factors that hamper the development of its faculties, and about those that stimulate its improvement. According to Fontenelle, cultivated minds possess the achievements and knowledge of all the minds that preceded them. It is the accumulation and the diffusion of knowledge that accounts for the transition from an enlightened mind to an enlightened century. 17 However, this transition presupposes another important transformation: what is in play is no longer a notion, according to which God, by his grace, touches the mind with his light; nor is it the Cartesian concept of a natural light that enlightens the mind by putting it in touch with clear and distinct ideas. From this point on, what matters is the production and the diffusion of knowledge. In order to be able to think of a "century of lights," one must be able to reflect on the means by which knowledge, emancipated from theology and speculative metaphysics, becomes recognized and disseminated in public. In the scientific domain, the perception of an epistemological rupture that occurred thanks to individual geniuses (the Galilean, Cartesian, or Newtonian "revolution") often takes priority over an analysis of the cultural and political conditions of the production of knowledge. The reception of scientific texts should be conceived of as a process of transmission in the context of academies and learned societies. However, when it comes to evaluating works of art, there needs to be a criterion of merit that does not solely consist in the understanding of a single individual, who secretly engages in observation in his study or undertakes experiments in a laboratory.

What is the appropriate tribunal in this case, and where might one find a qualified judge? For the ancients, who saw themselves as the heirs of Bacon and Descartes, this court was undoubtedly the tribunal of reason. Nicolas Malebranche testified to this in the preface to De la recherche de la vérité (1674). He presented God as the source of "the light of truth that enlightens the whole world," 18 because even those who are plunged in vice remain united to the truth. 19 Saint Augustine served as Malebranche's source here: it is the burden of the body and of the sensible world that prevents human beings from contemplating the eternal truth; it is the body that pulls man away from the presence of God "or from the interior light that enlightens him." 20 Man is constantly at risk of being blinded by the senses, by the imagination, and by the passions. 21 It is thus necessary to make sure that reason does not get lost or blind itself with the false glamor of the imagination: "It is necessary that the mind judges all things according to the interior lights, without listening to the false and confused testimony of the senses and of the imagination; and [that] it examines all the human sciences according the pure light of truth that enlightens it…" 22 What then is the proper criterion of truth? And how can it be recognized in an age of corruption? In a crucial passage in the same preface, Malebranche associated the theme of light with that of a tribunal (of reason) that could offer judgments that opposed established opinions. 17 Bernard le Bovier de Fontenelle, Digression sur les Anciens et les Modernes, in OEuvres de Fontenelle (Paris: Fayard, 1991), v.2, 425-426, n. s. "La comparaison que nous avons de faire des hommes de tous les siècles à un seul homme, peut s'étendre sur toute notre question des Anciens et des Modernes. Un bon esprit cultivé est, pour ainsi dire, composé de tous les esprits des siècles précédents; ce n'est qu'un même esprit qui s'est cultivé pendant tout ce temps-là. Ainsi cet homme qui a vécu depuis le commencement du monde jusqu'à présent, a eu son enfance, où il ne s'est occupé que des besoins les plus pressants de la vie; sa jeunesse, où il a assez bien réussi aux choses d'imagination, telles que la poésie ou l'éloquence, et où même il a commencé à raisonner, mais avec moins de solidité que de feu. Il est maintenant dans l'âge de la virilité, où il raisonne avec plus de force, et a plus de lumières que jamais." 18 Nicolas Malebranche, De la recherche de la vérité, in OEuvres complètes (Paris: Gallimard, 1979), v.1, 8. 19 Ibid. 20 Ibid., 10. 21 Ibid., 12.

Malebranche affirmed that one must not be afraid, when rendering one's work public, of shocking opinions established over the course of centuries:

So that my hopes are not in vain, I give this counsel: that you should not be immediately repelled if you find here things that shock the ordinary views that you have held your whole life and that you have seen generally approved by all men down through the ages.

For these are the most general errors that I mainly seek to destroy. If men were fully enlightened, then universal consent would be a [valid] argument; but just the opposite is the case. Be advised them once and for all, that only reason should stand in judgment on all human opinions that are not related to faith, in which God alone instructs us in an entirely different way from that in which he reveals natural things to us. Let us enter into ourselves and draw near the light that constantly sines there so that our reason might be more illuminated. 23 The tribunal of reason thus stands against the tribunal of opinion, because reason alone is the source of lights, and opinion has no legitimacy in the search after the truth. However, this postulate of a solipsistic reason that is in touch with its own light, was called into question in considerations concerning the enlightened century that could grant a positive value to the judgments of opinion.

After the Quarrel of the Cid, which saw the first appearance of the concept of a "public," called upon to judge literary works,24 the role of the Quarrel of the Ancients and the Moderns became crucial: for if Descartes left questions of taste outside the scope of evidence, the criterion for judging literature and art was even more uncertain. Malebranche furtively took on this question by siding against the ancients and against the testimony of authority: it is absurd to imagine, he claimed, "that the ancients were more enlightened than we could ever be, and that there is nothing to be achieved in matters where they did not succeed." 25 But in questions that do not concern science and philosophy, should the tribunal of reason take precedence over the tribunal of opinion? If the criterion for evaluating the quality of literary and artistic works is no longer one of objective certainty that can be guaranteed by one's inner conscience, then it can become something that issued by the public, and thus by public opinion.

II. The Quarrel of the Ancients and the Moderns

In one sense, the nineteenth-century debates about which thinkers were and were not part of the Enlightenment had an antecedent in another, earlier exercise of inventory. Just as the Enlightenment was invented through reflections on the philosophical origins of the French Revolution, the notion of an enlightened century developed out of the critique of the great thinkers (philosophers, orators, and poets) of antiquity, who were accused of not conforming to the ideals of refinement, politeness, and gallantry of the age of Louis XIV. This critical inventory allowed for the deployment of a self-reflexive analysis on the century. The Quarrel was particularly important in reflecting on the technical and scientific progress and of the fine arts, especially of poetry and eloquence. By provoking a rupture in the imitation of ancient models, the proponents of modern knowledge and the institutions that supported them allowed for the improvement of the arts.

This question first appeared in the polemical exchange between Charles Perrault and Longepierre, an eminent translator of ancient Greek works who immediately responded to the Siècle de Louis-le-Grand (1687). Perrault claimed that it was necessary to abandon the errors of the past and to rely on one's own lights. Longepierre responded in his Discours sur les Anciens (1687) by claiming the force of the lights for the Ancient party.26 However, the lights upon which he relied were the experience of the Ancients, and they stood opposed to the "lights of reason alone" that the Moderns championed. [START_REF]Longepierre asks: "…n'est-ce pas en quelque manière prostituer la raison que de leur en opposer les lumières, qu'ils font vanité de mépriser[END_REF] By denouncing the blind presentism of the Moderns, which he attributed to their pride, Longepierre maintained that "the greatest men have regarded the Ancients as a source of light, as the only rule of good taste, and as the sanctuary of right reason and good sense." 28 He retraced the brief history of the West, noting the rebirth of lights after a period of medieval barbarism: "The dark forces of ignorance and barbarism were soon entirely dispersed by such an abundant source of light." 29 It was necessary to turn to the Ancients, because enlightened men who had taken them as a model in the past could not have been misled. Universal consent served as the guarantor of the truth. 30 Of course, "the torrent of opinion" was not a certain mark of the truth, but it allowed one to attain a level of reasonable verisimilitude. To prove the contrary, Longepierre insisted, "it is necessary to clearly convince me that the esteem we have for the Ancients hurts the lights of reason," which could not be the case. 31 It was also important to trust the heart, which judged beauty without error, he maintained: "if the mind and reason can be and are always seduced by the false light that only enlightens them in order to deceive them," the heart, by contrast, cannot err. 32 From this it followed that in judging the quality of artistic and literary productions, the tribunal of opinion that favored the Ancients could not be eclipsed by the tribunal of reason.

The Moderns were thus not alone in claiming to possess the lights. In making the case against universal rationalism, the Ancients were driven to justify the historical and cultural relativity of customs and traditions. As Larry Norman has recently shown, their loyalty to ancient models of conduct drove them to form a self-reflexive awareness of the unique nature of their own nation and their own age. Without advocating for a "counter-culture" that could call into question the legitimacy of the absolutist regime, and without freeing themselves of the strategies of cultural hegemony, the partisans of Homer, who refused to accept the disparagements cast on the "barbaric" centuries, contributed to the emergence of a historical consciousness that was not reducible to naive progressivism. A partisan of the Ancients such as the abbé Dubos, who intervened in the second phase of the Quarrel, offered a profound reflection on the century of lights. [START_REF]The Quarrel is traditionally divided into two phases. The first part, 1687-1694[END_REF] It was informed by a novel distinction between the physical and moral causes of genius. A disciple of Locke and, in this sense a Modern, Dubos was quite familiar with the English empiricists. However, he remained a steadfast supporter of the Ancients in matters of aesthetics. According to Dubos, progress in the natural sciences came as a result of the accumulation of discoveries. At the same time, he argued, the poets and orators of Louis XIV's century did not surpass their ancient predecessors: "we do not reason better than the ancients in matters of history, politics, or civic morals." [START_REF] Dubos | Dubos was elected to the Académie française in 1720 and named perpetual secretary in 1722. His Histoire critique de l'établissement de la monarchie française dans les Gaules (1734) was analyzed and criticized by Montesquieu: see Céline Spector, Montesquieu. Liberté, Droit et histoire[END_REF] As a result of his research into the physical and moral causes of the superiority of the "illustrious centuries," that have featured numerous geniuses, Dubos claimed "that the veneration for the great authors of Antiquity will always last" and asked "whether it is true that we reason better than the ancients." [START_REF] Dubos | faire que les causes physiques aient part à la destinée des siècles illustres…[END_REF] Thus, while Dubos recognized that natural philosophy has improved since antiquity, he did not argue that there had been a general progress of reason or of the arts. 36 In his view, factual knowledge could be accumulated over time, but individual minds remained the same. Of course, one could certainly praise the moderns when it came to the art of reasoning and the method for acquiring knowledge:

If one is to judge by the state of the natural sciences, [it is clear] how much our century is more enlightened than the ages of Plato, Augustus, and Leo X. The perfection to which we have been carried by the art of reasoning that has allowed us to make so many discoveries in the natural sciences is a fertile source of new lights. These lights already spread themselves on the belles-lettres and they make old prejudices [in that domain] vanish as they did in the natural sciences. The lights will pass on to different professions, and one can already perceive the twilight in all situations. 37 But does this mean that human beings have necessarily become wiser or more reasonable? One must not confuse the amount of knowledge possessed by people in a particular age with reasonableness, Dubos insisted: "Our century may be more knowledgeable than those that preceded it, but I deny that today, generally speaking, the minds have more insight, more uprightness, and more precision than they did in the past. Just as the most learned men are not always those that have the most sense, so the century that is most knowledgeable than others is not always the most reasonable century." 38 If we surpass the Ancients with respect to "speculative reason," they outdo us in "practical reason." 39 Dubos thus contemplated the meaning and significance of the terms "enlightened century" or the "century of lights" well before the official appearance of "the Enlightenment" as a historical category. The century that inherited the discoveries of Bacon and Descartes, of Harvey and Copernicus, could be called the "century of lights," in so far as it witnessed the improvement in the natural philosophy. However, the dissemination of these lights did not necessarily form enlightened minds. In this sense, it is necessary to reject the thesis according to which the emergence and spread of the "philosophical spirit" produced a scientific, artistic, moral, and political rupture. Indeed, Dubos observed, its perverse effects could even spark a new age of barbarism:

This date of seventy years [circa 1650] that we give to the age of this supposed renewal of the minds is poorly chosen. I do not wish to enter into odious details about the states and about the particulars, and I will content myself with stating that the philosophical spirit, which renders men so reasonable and, so to speak, so logical, will do the same thing to a great part of Europe that the Goths and the Vandals had done, assuming that it continues to make the same advance that it has for the last seventy years. I see essential arts being neglected, prejudices most useful to the preservation of society abolished, and speculative reasoning preferred to practical [matters]. We conduct ourselves without regard for experience, which is the best teacher that humankind has ever had, and we imprudently act as if we were the first generation that has known how to reason. The concern for posterity is entirely neglected. 40 Thus, well before Rousseau, Dubos refused to grant the Moderns an exclusive claim to progress. 41 The generation that considers itself a pioneer conceals the negative effects of a one-sided and impoverishing development of reason; it praises itself all the more comfortably if it lacks vision and depth of field. Had not the Romans conceive of their period as a century of lights inherited from the Greeks? Dubos invoked Quintilian:

The latest inventions [the compass, the printing press, glasses…] spread a marvelous light on the knowledge that we already had. Luckily for our century, it finds itself at a time of maturity, when the progress of the natural sciences was at its fastest. The lights resulting from the preceding inventions, each of them having caused a separate advancement, began to combine eighty or a hundred years ago. We can say about our century what Quintilian said about his: 'Antiquity has furnished us with so many materials, so many examples that one could not, it seems, be born in an era that is more favored than our own, since the preceding ages have worked towards its instruction.'42

Ultimately, the very expression "century of lights" is at stake in this polemic. The possession of lights is the object of a veritable battle among the savants. The phrase is claimed by all sides to the point that its use becomes purely ideological: "Our savants, much like the ancient philosophers, do not agree about the facts, and they mutually refute one another concerning all that can only be known by way of reasoning, each treating the others as if they were voluntarily blind and refused to see the light. […] Those who praise so strongly the lights that the mind has spread over our century might reply that they understand nothing else by 'our century' than themselves and their friends and that one must not consider all others who are not in agreement with them on all matters, such as the Ancients, to be philosophers." 43 Dubos clearly conceptualized the ideological use that could be made of a notion such as "the century of lights," when the phrase was claimed and deployed by those who categorically supported the absolute validity of their own philosophical position.

III. The Public and Public Opinion

The debate concerning the meaning of the phrase "to be from one's own century" thus took place during the Quarrel of the Ancients and the Moderns. It was not enough to know the extent to which an author might be able to escape his own age-to know if Homeric poetry was necessarily barbarous, to the point where the modern public could not help but be outraged by the coarseness and irrationality of the heroic ages. It was also necessary to justify the criterion of judgment that would establish the superiority of one's own century.

Once again, Dubos provides invaluable assistance: his Réflexions critiques sur la poésie et la peinture questions the claims and pretentions of reason in the domain of fine arts. Can the jurisdiction of reason extend beyond the science of nature and become the sole tribunal before which all the creations of the human mind must appear? Dubos categorically denied this. In the second part of the Réflexions critiques, he defended the idea according to which feeling (or sentiment) was the only appropriate judge for evaluating the merit of literary and artistic works. Section XII proposed two different adjudicators for assessing the productions of the human mind: professionals and "the public." However, only the public could properly judge works according to their true worth, unless it were corrupted by the opinions of the critics. In artistic matters, the manifestation of the truth was hampered by the untimely use of critical reason that plunged the public into uncertain and made it founder in error, until sentiment finally managed to take back its rights.

And so, we might attempt the following hypothesis. The sense of what "an enlightened century" or "a century of lights" was took shape at the moment when a two-dimensional right of inventory emerged: on the one hand, it concerned the heritage of the Ancients, and, on the other hand, it dealt with the legitimate claims of reason to judge the works of another time period. By making sentiment the rightful criterion for evaluating beauty that moves and touches us and by rejecting the claims of critics to evaluate non-scientific works of genius, Dubos offered a new sense of the term "public" that helped to constitute an enlightened century with its judgments. 44 A public that was capable of appreciating the excellence of art was a public that would patronize artistic and literary productions and form a new kind of a public space. 45 It was limited in size, since the public was not the same thing as the people: "the word 'public' only included people who had already acquired lights, either by reading or by their experience in the world." However, this audience could become more democratized with time, as literary and artistic works became diffused more widely: "the public in question here is confined to people who read, who are familiar with theatrical plays, who see and discuss paintings, or who have acquired, by whatever means, the discernment known as 'the taste of comparison.'" [START_REF] Dubos | [END_REF] Following Longepierre, Dubos considered that the heart, enlightened by experiences, was the true organ of truth in aesthetic matters.

Finally, the lights invoked by Dubos can be understood as the refinement of artistic sensibility. The result is paradoxical: if the century of lights was not the age of reason or of the philosophical spirit, it took many lights to attain the ability to judge well and to constitute a lucid tribunal of opinion. The lights discharged for ideological use reappeared in practical form, associated with the experience necessary to evaluate the merit of artistic and literary productions. The tension thus reaches its highest point: it was by defending the Ancients that Dubos contributed to the invention of what constituted one of the words characteristic of modernity after 1750-that is to say, "public opinion," established as the sovereign judge and tribunal capable of evaluating the aesthetic and political creations of the human mind. [START_REF]L'espace public. Archéologie de la publicité comme dimension constitutive de la société bourgeoise, trans[END_REF]

Conclusion

Following Habermas, Ricuperati has unearthed the authors who have analyzed the legacy of the philosophical spirit after the death of Louis XIV, and he has described the eighteenth century as the moment of the emergence of public opinion. [START_REF] Lerminier | De l'influence de la philosophie du XVIII e siècle sur la législation et la sociabilité du XIX e siècle[END_REF] However, critical reflections concerning the beneficial and harmful effects of the philosophical spirit appeared before the birth of the historiography of the Enlightenment and before the emergence of theories about the relationship between the philosophes and the French Revolution. The aim of this essay has been to show that the Quarrel of the Ancients and the Moderns had posed this question in an unprecedented way and to highlight the role that the abbé Dubos played in the emergence of reflections about "the century of lights." Even if he had witnessed a social and cultural evolution of a greater scale, Dubos remained pioneer. His reflections on the ambivalent nature of the philosophical spirit brought together analyses of the social, political, and cultural conditions that produced a learned elite. His examination of "the public" revealed the important attention paid to the role of feeling and sentiment in the creation of the Enlightenment.

Far from seeking to defend the Ancients, in the manner of Marc Fumaroli or Larry Norman, this essay has tried to reestablish the origins of historical self-reflexivity. The emergence of the concept of public opinion-a process that occurred before the appearance of the actual phrase in the 1750s-remains to be studied. Casting off the tutelage of traditional authorities, the public became the only sovereign authority for judging the merits of the creations of the human mind. It did so by daring to use not only its own understanding but also its own feelings. 49

« The "Lights" before the Enlightenment: The Tribunal of Reason and Public Opinion », in Let There Be Enlightenment, A. Matytsin et D. Edelstein éds., Baltimore, Johns Hopkins University Press,

2018, p. 86-102. This article is a revised version of a contribution that appeared under the title "Les lumières avant les Lumières: tribunal de la raison et opinion publique."(http://revolution-francaise.net/2009/03/01/299-les-lumieres-avant-les-lumieres-tribunal-de-la-raison-etopinion-publique).After having written this essay, I have learned of an existence of an article by D. Ribaud entitled "Les lumières avant les Lumières? Historiographie de l'opinion publique et discours d'auteurs (dix-septième siècle)," in SVEC 2006:12, 65-74. However, the subject matter discussed there is of radically different nature from my topic here. The article was translated from French by Anton M. Matytsin. 2 See Fritz Schalk, "Zur Semantik von 'Aufklärung' in Frankreich," in Festschrift W. Von Wartburg (Tübingen: Niemayer, 1968), 251-266; Jacques Roger, "La lumière et les lumières," in Cahiers de l'Association internationale des études françaises XX (1968): 167-177; Roland Mortier, "'Lumière" et 'Lumières', histoire d'une image et d'une idée au XVII e et au XVIII e siècle," in Clartés et ombres du siècle des Lumières (Geneva: Droz, 1969), 13-59; Michel Delon, "Les Lumières. Travail d'une métaphore," in Studies on Voltaire, no. 152 (1976), 527-541. For more on the historiography of the Enlightenment and its link with the debates about the origins of the French Revolution, see Vincenzo Ferrone and Daniel Roche, "Le XIX e siècle: l'identité refusée. Les Lumières et la Révolution française," in Le Monde des Lumières, ed. Vincenzo Ferrone and Daniel Roche (Paris: Fayard, 1997), 497-522. 3 Furetière's dictionary affirms that "when light signifies the belles connaissances of the mind, it should always appear in the plural." See Antoine Furetière, Dictionnaire universel (The Hague: Husson, Johnson, Swart, Van Duren, Le Vier, and Van Dole, 1690), v.3, Art. "Lumière." 4 Charles Sorel, De la connoissance des bons livres, ou Examens de plusieurs autheurs (Paris: Pralard, 1671), 454-455. 5 Pierre Bayle, "Vienne deux fois assiégée par les Turcs en 1529 & 1683 & heureusement délivrée, avec des Reflexions historiques sur la Maison d'Autriche, & sur la Puissance Ottomane, par. M. J.B. de Rocoles Hisoriographe," Nouvelles de la République des lettres (April 1684): 169-170.

Bernard Le Bovier de Fontenelle, "Réponse de Fontenelle à l'évêque de Luçon, lorsqu'il fut reçu à l'Académie française, le 6 mars 1732," in OEuvres de Fontenelle (Paris: Salmon, 1829), v.2, 442.

Voltaire, Art. "Gens de Lettres," in Encyclopédie, ou Dictionnaire raisonnée des sciences, des arts et des métiers, ed. Denis Diderot and Jean-Baptiste le Rond d'Alembert (Paris: Briasson, David, Le Breton & Durand, 1757), v.7, 599.

Jean-Baptiste le Rond d'Alembert, Essai sur les éléments de philosophie, ou sur les principes des connaissances humaines, in OEuvres complètes (Paris: Slatkine, 1967), v. I, 122. Also see the Correspondance littéraire, v. 10 (August 1774), 465.

Jean-Jacques Rousseau, Lettres morales, in OEuvres complètes (Paris: Gallimard, Bibliothèque de laPléiade, 1969), v.4,

The interpretation of the Quarrel as a fin de siècle culture war appears in Joan Dejean, Anciens against Moderns. Culture Wars and the Making of a Fin de Siècle (Chicago: The University of Chicago Press, 1997). Dejean supports the perspective of the Moderns by proposing a gendered analysis of the Quarrel. By contrast, Larry Norman attempts to change our view of the Quarrel by pointing to the shock experienced by the Ancients, who were hardly traditionalists. Norman sees the partisans of the Ancients as the precursors of historicist thinking, who were able to perceive the radical otherness of the ancient world, and he presents the Moderns as more conservative and conformist. See Larry Norman, The Shock of the Ancient. Literature and History in Early Modern France (Chicago: The University of Chicago Press, 2011). For a nuanced critique of Norman's thesis, see: Marie-Pierre Harder, "Les Anciens contre-attaquent ou la Querelle revisitée," Acta fabula 13, no. 1. January 2012, URL: http://www.fabula.org/acta/document6731.php

For more on this semantic evolution, see Hillel Schwartz, Century's End: A Cultural History of the Fin de Siècle from the 990s through the 1990s (New York: Doubleday, 1990).

For a remarkable contribution on this topic, with which this essay is in great agreement, see Dan Edelstein, The Enlightenment: A Genealogy (Chicago: The University of Chicago Press, 2010).

Ibid.,[17][18] n. s.

See Dejean, Ancients against Moderns,34-35.

Malebranche, De la recherchede la vérité, v.1, 210-214.

Hillaire-Bernard de Longepierre, Discours sur les anciens (Paris: Aubouin, 1687), preface, n.p. "La vérité, surtout lorsqu'elle est aussi évidente qu'en cette occasion, a un certain éclat et une certaine force qui perce tous les nuages, et qui surmonte tous les obstacles qu'on ose en vain lui opposer. Elle frappe la vue de ceux même qui veulent fermer les yeux à sa lumière…."

Ibid., 454.

Ibid., 456.

Ibid.,[454][455] In the 1733 edition, Dubos modified the starting point: the century of lights started 80 years ago, in this edition, around 1650 or 1660. Perhaps Dubos had in mind the foundation of the royal academies in England and in France.

Ibid., 458. "Il suffit qu'un siècle vienne après un autre pour raisonner mieux que lui dans les sciences naturelles, à moins qu'il ne soit arrivé dans la société un bouleversement assez grand pour éteindre, au préjudice des petits-fils, les lumières qu'avaient leurs ancêtres."

Ibid.,[471][472]

Ibid.,[486][487]

In response to the Habermasian archeology, Joan Dejean brings up the origin of this new public space with the appearance of the Mercure galant, the most influential periodical on the French literary science between 1672 and 1710. She discusses the strategy of its editor, Jean Donneau de Visé, who encouraged his readers to send the journal collective letters that offered testimonies of their personal opinions. This was especially the case with the publication of La Princesse de Clèves in 1678. See Dejean, Ancients against Moderns, 57-65.


Mehena Oualit
email: oualitmehena@yahoo.fr

Raoul Jauberthie

Ed Tahar Abadlia

Concrete pathologies in sewer structures: Microstructural analysis

Keywords: Concrete sewer, SEM-EDS analysis, pathologies, durability, degradation

published or not. The documents may come

Introduction

The durability of concretes in sewerage networks is essentially linked to the presence of effluents rich in sulfur compounds, sources of an acid attack and cause chemical reactions that lead to the formation of expansive products [START_REF] O'connell | Biochemical attack on concrete in wastewater applications: A state of the art review[END_REF][START_REF] Grandclerc | Accelerated biodeterioration test of cementitious materials in sewer networks[END_REF]. The release of hydrogen sulfide can occur in septic tanks, sewage treatment plants and sewer systems. This release originates from the decomposition, in anaerobic environment (nonoxygenated environment), of the sulfur compounds contained in the effluents stirred or circulating in the structures.

Corrosion of concrete caused by hydrogen sulfide has been recognized as a serious problem in collection systems for the past century [START_REF] Olmsted | Converting portions of the Los Angeles outfall sewer into a septic tank[END_REF][START_REF] Parker | Species of sulphur bacteria associated with the corrosion of concrete[END_REF][START_REF] Okabe | Succession of sulfur-oxidizing bacteria in the microbial community on corroding concrete in sewer systems[END_REF]. The problem of hydrogen sulfide induced concrete corrosion is known in collection systems in most of the world [START_REF] Zhang | Chemical and biological technologies for hydrogen sulfide emission control in sewer systems[END_REF][START_REF] Brongers | Corrosion costs and preventive strategies in the United States[END_REF][START_REF] Herisson | Better durability of calcium aluminate cement regarding biocorrosion in sewer networks[END_REF]. In some of the worst cases, the lifetime of sewer pipes and pumping stations has been reduced to less than ten years [START_REF] Hvitved-Jacobsen | The sewer as a bioreactora dry weather approach[END_REF][START_REF] Olmsted | Converting portions of the Los Angeles outfall sewer into a septic tank[END_REF]. Besides the costs of restoration, the costs of preventive measures should also be considered when estimating the economic impact of hydrogen sulfide related problems [START_REF] Sydney | Control concrete sewer corrosion via the crown spray process[END_REF].

When hydrogen sulfide is taken up by the concrete pipe surface it is oxidized to sulfuric acid H2SO4. The oxidation of hydrogen sulfide on the pipe surface is biological after the pH of the surface has dropped below approximately 8-9 [START_REF] Parker | Species of sulphur bacteria associated with the corrosion of concrete[END_REF][START_REF] Okabe | Succession of sulfur-oxidizing bacteria in the microbial community on corroding concrete in sewer systems[END_REF].

The acid reacts with the alkaline components of the concrete, mainly calcium hydroxide and calcium carbonate. The product of this reaction is mainly gypsum [START_REF] Tazaki | Microbial jarosite and gypsum from corrosion of Portland cement concrete[END_REF][START_REF] De Graef | A sensitivity study for the visualization of bacterial weathering of concrete and stone with computerized X-ray microtomography[END_REF], which has little structural strength for which reason the concrete pipe is weakened [START_REF] Lea | The chemistry of cement and concrete[END_REF][START_REF] Parker | The Corrosion of Concrete. The Function of Thiobacillus-Concretivorus (Nov-Spec) in the Corrosion of Concrete Exposed to Atmospheres Containing Hydrogen Sulphide[END_REF]. Jarosite (KFe3(SO4)2(OH)6) and ettringite (Ca4Al2(SO4)(OH).2H2O) have also been identified as components in the corrosion products [START_REF] Tazaki | Microbial jarosite and gypsum from corrosion of Portland cement concrete[END_REF][START_REF] Davis | Analysis of concrete from corroded sewer pipe[END_REF][START_REF] Mori | Interactions of nutrients, moisture and pH on microbial corrosion of concrete sewer pipes[END_REF]. Figure 1 illustrates and summarizes the corrosion process that occurs in sewers and concrete structures. This paper presents a part of a vast preventive study on the aging of sewerage networks in the city of Rennes (France). It is dedicated solely to the detection of sewer concrete pathologies by microstructural analysis. The objective of this study is to highlight and identify the concrete pathologies of deteriorated sewer pipes. Two cases studied are presented in this research.

Materials and methods

General data and sampling

As maintenance work and sewer replacement work continues in the City, samples of pipe are recovered for analysis. For each sample taken back ground information is logged onto a data base: Specimens with a diameter of 28 mm were cored in recovered pipe samples. Cores were taken in three directions; Rradial, Ttransversal and Llongitudinal. The cores L and T taken from the pipe are used to assess alterations to the matrix of the concrete; those taken in the radial direction are used to study the alterations at to the external and internal faces of the pipe.


To study these alterations, the cores are examined by visual observation and scanning electron microscope (SEM) coupled with energy dispersal X ray spectroscopy (EDS).

In addition to these microstructural analysis, bulk density and water-accessible porosity tests are performed. The results obtained were compared with those of a reference concrete (new pipe, not yet in use).

Two examples are described in this paper. The first case, 'Rue Jean Ogée' concerns a conduct of a unitary network. The pipe section examined shows a slight deterioration of the internal surface and a significant damage to the outer portion with important section loss (of material). This section of the sewerage system was constructed in 1965 to serve an area of multistorey apartments. The pipe in question is 400 mm in diameter and 55 mm in thick; it forms the first pipe section in the pipe run with a gradient of 1.25%. The pipe collects from a population of approximately 150-200 people. The soil in the area from which the pipe was taken is clay resulting from altered biovérien schist.

The second case study 'Rue saint Helier' is a sample taken from a 1,680 × 800 mm ovoid-shaped piece of pipe from a unitary network. A very old pipe, set up since 1892 with a very important thickness estimated at 209 mm. The pipe consists of large red block likely sandstone or shale joined together by porous concrete. Takeoffs and cracks can be observed between the blocks and the binder. The outer surface is sandy and rough. The sewer has a catchment of 0.61 km 2 serving a population of 6000 inhabitants.

The pipe is located in a residential area and shops. This reach of the sewer is 48 m long and has a gradient of 3.75%. The soil in this area is a clayey subsoil, the clay emanating from altered biovérien schist.

SEM-EDS analysis

The SEM-EDS analysis are performed on the cylindrical samples (R) taken at midheight of the pipes. This zone is chosen because it is the most vulnerable [START_REF] Oualit | Performance and analysis of concrete in sewer environment: Anisotropy of damage[END_REF][START_REF] Oualit | External corrosion to concrete sewers: a case study[END_REF]. These analysis were carried out on fragments of samples that were previously subjected to indirect tensile strength using the Brazilian test method. Fragments of samples were taken from specific areas namely: proximity of the outer face, close to the inside and the median zone.

These samples are glued on a conductive support covered with a palladium gold Au-Pd conductor before launching SEM observations.

Apparatus and procedures

A conventional JEOL JSM 6400 SEM is used, allowing the observation of dry and conductive samples and atomic analysis by an INCA OXFORD Link energy dispersion spectrometer.

The final preparation of non-conductive samples is carried out by: -Drying of hydrated samples by Balzers CPD 010 critical point apparatus; -Sputtering metallization with JEOL JFC 1100 (conductive gold-palladium layer); -Carbon deposit per Emscope TB500 device (carbon conductive layer).

The observations are made either in secondary electrons or in backscattered electrons.

Results and discussion

SEM examination and EDS analysis: Case study 1

Outside area

The SEM analysis of a fragment of the concrete taken near the outer face of the pipe is illustrated in Figure 2. It may be noted that the concrete in contact with the ground of this pipe is slightly porous (Figure 2(b)). In Figure 2(a), the development of ettringite needles in a pore can be distinguished. An ettringitic nature confirmed by the EDS analysis (Figure 3) carried out on the point of spectrum 1 of the Figure 2(a), in particular with the presence of aluminum (Al) and sulfur (S). Moreover, the EDS analysis of the point of spectrum 2 in Figure 2(b) also shows the presence of portlandite which can be converted into calcite with the presence of CO2, its composition is shown in Figure 4.

Inner area

The visualizations performed on a fragment taken from the inner face of the pipe, Figure 5, reveal a formation of sulphates which appears in the form of needles (on the right of Figure 5(a)) with the chemical composition of ettringite (see Figure 6). On the other hand, the left part which appears in the form of a hard crystal is a mixture between CSH of cement and portlandite.

Moreover, Figure 5(b) shows the altered state of this zone with highly degraded and sulphated cement. The microanalysis at the point of spectrum 1 of Figure 5(b) is shown in Figure 7. In the case of 'Rue Jean Ogée', the sewer is at the head of a network and oversized for its function; a 400 mm diameter sewer to service a population of approximately 200 population. The consequence of this situation is that during the night the flow in the sewer will be virtually non existent, and any sewage retained in the reach will become anaerobic, a condition that will favour the generation of hydrogen sulfide gas and consequently lead to sulphate attack of the sewer lining. Being at the head of the sewer, the natural ventilation will be limited.

Median zone

Like the extremities, the central part of the sample contains abundant zones in the form of needles attributed to ettringite (Figures 8(a

SEM examination and EDS analysis: Case study 2

outside area

The outer part of the pipe shows a porous concrete with the appearance of even cracks in Figure 11(a). Crystals of calcite are visible in the same Figure 11(a), developed in their usual forms. In contrast, calcite mixed with cement paste is observed in Figure 11(b). The formation of calcite crystals is favored by the high porosity of the conduit material which facilitates the penetration of atmospheric CO2.

Inner area

Figure 12 represents the SEM observation of the internal part in contact with the effluents of the pipe. Overall, the concrete in this area is significantly altered and has irregularities.

According to Figure 12, hydrated calcium aluminates (CAH) are identified in the form of dense crystals, next to the latter; it can be also distinguish needles likely corresponding to ettringite. The EDS analysis of the points of spectra 1 and 3 of Figure 12 are given in Figures 13 and14, respectively, in which the chemical composition of the sub-cited products (ettringite and CAH) are confirmed. On the other hand, we can also note the presence of a small quantity of Si which means that hydrated calcium silicates are also present in this internal part of the sample.

Median zone

Like the internal part in contact with the effluents, the same products are detected in the middle of the sample, namely ettringite needles and hydrated aluminates and calcium silicates in the form of crystals as shown in Figure 15. The porosity of the concrete is high even at the central part of the pipe.

Density and porosity accessible to water

The results of the AFREM cross-tests for the determination of the apparent density and the porosity accessible to water of the specimens are given in Table 1. The tests were performed using the recommended AFREM procedure [START_REF] Ollivier | Les résultats des essais croisés AFREM pour la détermination de la masse volumique apparente et de la porosité accessible à l'eau des bétons [The results of the AFREM cross-tests for the determination of the apparent density and the water-accessible porosity of concretes[END_REF]. The value given represents the average of three samples.

From the results obtained, it is noted that the values of the porosity accessible to water of the concretes of service pipes (cases 1 and 2) are greater (twice as much) than the reference concrete (new pipe), this is an indicator of material damage knowing that open porosity is considered a first-rate parameter with regard to the durability of concretes.

On the other hand, the density values of the reference concrete are much higher. It may also be noted that the samples taken in the radial direction (R) are more affected by this alteration with larger values than those of the samples (T) and (L), this can be explained by the permanent contact of the ends of the (R) sample with internal and external environments that represent sources of aggressive agents. On the other hand, this anisotropy is not observed for the sample of the reference concrete where the values are almost identical in all directions and this is valid for the two properties (density and porosity).

Conclusions

The SEM and EDS analysis on the internal, external and middle faces of the thickness are performed and a report is produced in order to identify the phases present and detect the major pathologies on the micro scale.

Indeed, the degradations take different forms depending on the quality of the concrete, the nature of the network (unitary, rainwater or separative), the effluents, the soil and the support materials. Attacks and pathologies can be detected in areas in contact with soil or effluent. From this research, it could be concluded that:

 The surface of the external part is very often carbonated, with the formation of calcite crystals CaCO3 thus contributing to the decrease of the pH value of the concrete. Sometimes, the carbonation reaches even the central part of the sample.

 The internal face of the pipes is often degraded by the sulphates present in the effluents. The presence of sulphates with high concentrations reacts with the portlandite Ca(OH)2 of the cementitious matrix to form fibrous gypsum.

 External corrosion of the sewer has been noted within the networkthis requires further analysis to identify the cause. There are potential problems with pyrite from the native sub soils, altered biovérien schist; there is also the possibility of pyrite contaminated backfills being used. In the area of Rennes crushed rock used for backfill, such as Horsfel or schist, may have pyrite contamination. It is recommended that in future soil sample and backfill are recovered for analysis.

 SEM observations confirmed the presence of ettringite in its characteristic form (needles). Its chemical composition is confirmed by microanalysis (EDS). This ettringite can be primary training or secondary training. The latter is an expansive product, which can cause cracks and damage to the structure.

 In sewage conditions, the degradation of concrete is mainly summarized by the action of a double attack, acid and sulphate. This double mechanism of acid and sulphate attacks can be written in a simplified way as follows:

- Meau: Mass of the sample weighed under water, (hydrostatic weighing), (g).

Mair: Mass of the saturated sample weighed in air, (g).

Msec: Mass of the dry sample, (g).

ρd: Bulk density, (g/cm 3 ).

ε: Porosity accessible to water, (%).

  Catchment typeseparate or combined sewerage.  Catchment area, population and industrial waste discharges.  Physical pipe detailsdiameter and gradient.  Date of construction.  Local soil conditions.

  ) and 8(b)). The chemical compositions of the needles observed are given respectively in Figures9 and 10where the ettringitic nature of the needles observed is confirmed.

Figure 3 .

 3 Figure 3. EDS analysis performed at spectrum point 1 of Figure 2(a) with details of the compounds.

Figure 4 .

 4 Figure 4. EDS analysis performed at spectrum point 2 of Figure 2(b) with details of the compounds.

Figure 5 .

 5 Figure 5. SEM visualizations of a concrete fragment located near the inner face.

Figure 6 .

 6 Figure 6. EDS analysis performed at spectrum point 1 of Figure 5(a) with details of the compounds.

Figure 7 .

 7 Figure 7. EDS analysis performed at spectrum point 1 of Figure 5(b) with details of the compounds.

Figure 8 .

 8 Figure 8. SEM visualization of a fragment of concrete located at the central zone.

Figure 9 .Figure 10 .

 910 Figure 9. EDS analysis performed at spectrum point 1 of Figure 8(a) with details of the compounds

Figure 12 .

 12 Figure 12. SEM visualizations of a concrete fragment located near the inner face.

Figure 13 .

 13 Figure 13. EDS analysis performed at spectrum point 1 of Figure 12(a) with details of the compounds.

Figure 14 .

 14 Figure 14. EDS analysis performed at spectrum point 3 of Figure 12(b) with details of the compounds.

Figure 15 .

 15 Figure 15. SEM visualization of a fragment of concrete located at the central zone.

  Acid attack: dissolution of hydrated lime with formation of gypsum

	Figure 1. Process and corrosion mechanism that occurs in sewers concrete structures.
						sulfur-oxydizing bacteria
			Coring
					H 2 S+2O 2	H 2 SO 4
	Concrete					H	2 S
	Ettringite	Ca(OH)2 + H2SO4	SO	4 -2	CaSO4 + 2H2O + Org S H 2 S
	Gypsum
	-Sulphate attack: reaction between cement aluminates (C3A) and gypsum to
	form secondary ettringite. Biofilm	Sulphate reducing bacteria
	3CaO.Al2O3 + CaSO4 + 32H2O	3CaO.Al2O3.3CaSO4.32H2O
			H2S + 2O2		Sulfuric acid H2SO4
	Oxidation	Sulfur-oxidizing bacteria H2S + 2O2
		H2S + 2O2		H2SO4
				Sulfides
		H2S		H + + HS -	2H + + S -
		sulphate-réducing bacteria	Reduction
		H2S	H + + HS -		2H + + S -2
			Sulphates (SO4 -2 )
			Sulphites (SO3 -2 )
			Sulfites (SO3 -2 )

Table 1 .

 1 Results of cross-tests of apparent density and porosity accessible to water.

	Element Mass%	Atomic%
	O K	75.89	87.47
	Al K	3.81	2.61
	Si K	1.00	0.66
	S K	3.39	1.95
	Ca K	15.91	7.32
	Totals	100.00

Acknowledgements

This work was done at the Laboratory of Civil Engineering, Mechanical Engineering (Materials) of the National Institute of Applied Sciences (INSA) of Rennes (France). This work is part of a research project between INSA and the City of Rennes. The authors would like to warmly reiterate all the staff of the center with these different laboratories as well as the Faculty of Sciences of the Rennes University.

Conflict of interest:

On behalf of all authors, the corresponding author states that there is no conflict of interest.