Abstract. Baron d’Holbach was a critic of established religion, or a philosophe, in late 18 th-century France. His work is often perceived as less inventive than the work of other materialist philosophes, such as Helvétius and Diderot. However, I claim that d’Holbach makes an original, unjustly overlooked move in the criticism of religious moral teaching. According to the materialist philosophes, this teaching claims that true happiness is only possible in the afterlife. As an alternative, Helvétius and Diderot offer theories according to which the experience of pleasure constitutes happiness, the end of all human desire. In contemporary terms, these theories would represent psychological hedonism. But, as Diderot himself admits, they have a problem in accounting for why people seem to naturally regard some pleasures as preferable to others. I argue that in response to this challenge, instead of accepting the psychological hedonism of his fellow materialists, d’Holbach shows how one can abstain from reducing happiness to pleasure and yet remain a materialist.
Keywords: Denis Diderot, Enlightenment, happiness, hedonism, Claude Adrien Helvétius, materialism, Paul-Henri Thiry, Baron d’Holbach, religion.
Baron d’Holbach is often regarded as a less original critic of religious moral teaching than Diderot or Helvétius.  In this article, I claim, however, that d’Holbach does not lack originality and should be credited with an important move in moral theory: he severed the connection between the pleasure-centered ethical theories of Helvétius and Diderot and the natural scientific picture of the world by showing how one could endorse materialism – the thesis that only matter exists – without thereby equating happiness with pleasure. In contemporary terms, the kind of hedonism discussed by these three philosophes would amount to “psychological” or “descriptive” hedonism, as opposed to its “normative” kind. It claims that human desire is directed at happiness (bonheur), which is pleasure, but does not present us with an obligation to maximize the quantity of pleasure.
My article begins with a brief overview of the nature of the critique of religious moral teaching by the above-mentioned philosophes. Although they all refer generically to la religion in their criticism, in practice they had Roman Catholicism in mind. The main problem that they perceived in religious moral teaching was its anthropology that was, according to them, based on outdated theology, lacking in historical erudition and ignorant of contemporary natural science. This was at odds with the philosophes’ materialistic vision of human nature, which they perceived as the reappraisal of the ancient Epicureanism.  In line with this vision, the philosophes took providing a description of human psychology that does not resort to the authority of the religious teaching as their task.
The philosophes had inherited from their own scholastic education the theory that happiness is the summum bonum, the final end of human desire.  But their conception of happiness differed from the traditional religious conception, according to which we can be truly happy only in the afterlife (visio beatifica).  Although the philosophes disagreed about many things, they agreed that the religious conception undermines our motivation to act morally by ignoring our natural desire for a pleasant life and presenting suffering as the earthly consequence of being moral.
The rest of the first part of my article presents Helvétius’ and Diderot’s justifications for their criticisms of the religious moral teaching. They both regarded pleasure (plaisir) as a mental state that arises from the satisfaction of desires and lasts as long as a desire remains satisfied or is replaced with another.  According to Helvétius, the real purpose of religion is to promote the interests of rulers, which do not coincide with what their subjects desire, and the moral language created by priests serves this aim by presenting virtue as incompatible with satisfying one’s earthly desires. Diderot was less critical of the pre-existing moral language. His main concern was that the religious moral teaching could be mistaken in condemning our desire for pleasure while praising virtue, because this contrast can be artificial. Diderot suggested, possibly on the basis of his own experience, that human experience shows that the pleasure of virtuous acting is preferable to all other pleasures.
In the second part, I proceed to d’Holbach’s critique of the religious moral teaching. The baron’s argumentation seems to have taken elements from both Helvétius and Diderot. From Helvétius, the baron adopted the conviction that our conception of the relationship between virtue and pleasure is corrupted by the hypocrisy of the priests, and from Diderot – the view that traditional virtues are nevertheless beneficial to us insofar as they consist in helping others, for helping others is by nature pleasant. At face value, d’Holbach seems to have a conception of virtue that is very similar to the conception of Diderot. I suggest, however, that this first impression is misleading, because d’Holbach was aware that Diderot’s account of virtue as the source of the most preferable kind of pleasure was incompatible with the baron’s ambition of building a coherent materialist justification for morality. Diderot’s personal experience is not a sufficient justification for the claim that pleasure from virtue is preferable to pleasure that originates from vice. There are also people that have contrary experiences, and in order to discount their experiences, it seems that a philosopher would need to go beyond physical nature, and resort to a metaphysical thesis that some pleasures have less intrinsic value than other. However, a materialist philosopher cannot support such a thesis. Building an empirically justifiable conception of virtue was thus the challenge that d’Holbach faced as a materialist, who wanted to avoid Helvétius’ reduction of moral language to a tool of promoting the interests of the rulers.
The third part of my paper is dedicated to showing d’Holbach’s hitherto unacknowledged reply to the above challenge. In contrast to Helvétius or Diderot, the baron abstains from explicitly equating happiness with the experience of pleasure. He even separates happiness from pleasure. Instead of pleasure, happiness is self-preservation, and virtue means having the mental state that is conducive to self-preservation. According to d’Holbach, virtues do not yield pleasure, but are only accompanied by it: in order to maintain one’s existence, one has to fulfil certain desires, and this fulfilment, not virtue as such, produces experiences of pleasure. It remains possible that vicious traits that produce harm are more pleasant than virtues. Since the contribution of one’s mental state to one’s self-preservation is potentially measurable, d’Holbach’s conception of happiness that eschews psychological hedonism is, I conclude, in principle compatible with materialism.
In late 18 th-century France a new form of religious criticism emerged: a group of intellectuals, collectively known as philosophes, began to argue that “the religion” (la religion) – by which they meant unquestioning allegiance to the official, Catholic Church – is harmful to society. Although the arguments that the philosophes utilised for criticizing the religion differed, they nevertheless formed a definable group, because most of them were connected with one person: Paul-Henri Thiry, baron d’Holbach. From 1750 until the ‘80s, he had a habit of inviting thinkers of diverse social standing and philosophical views for lavish dinners at his home at Rue Royale in Paris twice a week.  Diderot, Helvétius (whenever he was in Paris) and Marmontel were among regular attendees, d’Alembert, Rousseau and many others attended more or less occasionally.  The baron’s house was also where some of the dinner participants could have embarked on the project of compiling the Encyclopedie under the editorship of Diderot and d’Alembert.
The philosophes sought to weaken the influence of the religion through education and they envisaged that the Encyclopedie was to provide the factual basis for the new, moral education.  In France, the Catholic Church was the dominant educational institution, and the Church – at least so the philosophes perceived it – promoted the kind of moral teaching which was harmful to people due to its theological presuppositions that discouraged people from discovering true moral principles with their own reason.  One of such presuppositions, according to the philosophes, was that “virtue” not only consists in socially beneficial actions, but also demands abstinence from many earthly pleasures – even if they harmed no one – for the sake of securing eternal happiness. The project of the philosophes was not helped by the fate of the “Catholic Enlightenment” that had aimed at easing the emerging conflict between the Church and the new currents of philosophy. It was stifled at the same time when the work on the Encyclopedie was under way, as a reaction to Abbé Prades scandal (1751), Damiens affair (1757) and the condemnation of Helvétius’ l’Esprit (1759). 
For those philosophes that based their criticism of religion on empiricism and materialism, most prominently Helvétius, Diderot, and d’Holbach himself, the religious teaching on pleasure was incoherent, which they regarded as a cause of hypocrisy. Since we can only abstract the idea of eternal happiness from the pleasures that we have experienced in our lives, we cannot sincerely exalt the latter while condemning the former. According to the materialist philosophes, pleasure – any pleasure – is a mental state that occurs when a desire is satisfied. However, once we have satisfied a desire, we, as active beings, begin to desire something else, because the prospect of a new pleasure overwhelms the existing pleasure.  The adoption of this, originally Hobbesian, conception of pleasure as a fragile, “restless” mental state  among the materialist philosophes was inspired by the progress in empirical sciences, which, as they thought, had made metaphysical explanations of natural phenomena obsolete. The materialist philosophes were convinced that the same would happen in ethics as well, that the dualism of earthly pleasure and eternal happiness would disappear, and the pursuit of the former would be acknowledged as the basis of morality.
Even those philosophes that were not inclined to endorse all-encompassing materialism, the most famous of whom was Rousseau, accused the religion of incoherent moral teaching, although with different arguments. Rousseau argued in Emile (1762) that if the religious moral teaching had not distorted our self-image by blaming us of our natural desires as it did, we would become happy by living according to the desires with which God has endowed us.  However, since pleasures are transient, happiness cannot be found in pleasure,  but in “recollecting” (rassembler) one’s natural desires and limitations with acceptance.  Perhaps Rousseau had the Socratic ideal of “knowing thyself” in mind.  He also affirmed that true religion is not a matter of endorsing the dogmas that the Church teaches. It is a private encounter with God that takes place when we “behold the spectacle of nature” or “listen to the inner voice,” i.e. conscience.  The religion of the Church was for Rousseau, like for other deist philosophes, such as Marmontel and Galiani, a system of propositions about God that is based on a flawed understanding of the essence of religion; true religion does not contain any universal dogmas, but consists of private experiences of the sublime. Since the ecclesiastical religion seeks God where He cannot be found, from vague, abstract dogmas instead of immediate experiences, following it brings no happiness, but produces harm by trying to prevent us from accepting ourselves as we are. 
The materialist philosophes opposed also deistic arguments. Claude-Adrien Helvétius, who had become (in)famous due to the condemnation of his work l’Esprit in the appellate court (parlement) of Paris in 1758,  went as far as to propose that any religion is arbitrary. According to him, we have an inclination to interpret natural phenomena and conscience as the expression of divinity, but this is not inevitable: we have such an inclination only because we have adopted a religious worldview in the first place. In its natural state, human mind is a tabula rasa as already Locke had argued, but according to Helvétius’ more extreme position that even d’Holbach rejected, we not only lack any innate ideas, but are also naturally equal in intelligence.  We would use our reason for selecting the optimal means to satisfying our desires if the religious moral teaching had not corrupted it by encouraging us to curb our supposedly “vicious” desires for the sake of developing a “virtuous” character.  The language of “vice” and “virtue” is artificial, because we only consider virtuous what we think is our best interest to do.  Our negative judgments about the worth of satisfying our desires, and our emphasis on the divinity of certain human capacities – such as conscience – instead of others, are superstitions that prevent us from concentrating on the pursuit of our interests.  Although pleasure is transient, it is nevertheless what we desire, and many people become unhappy on account of sacrificing pleasures in the hope of an imaginary gain.  The entire society, thinks Helvétius, suffers from pretentious moral language created by the priests in order to safeguard the interests of the rulers who promised eternal life to those that obey them, thus helping them in this pursuit.  Because people want to live forever, they obeyed the priests. So as to make people abstain from pleasures (and leave them to the priests and rulers), the priests devised a dualistic theory of human psychology, which is false, because in reality all our needs and wants are bodily.  However, even if there were a religion that rejected the division between the “sinful” body and the “divine” reason, like Rousseau’s, it would not be “useful” unless it claimed no more than that “the will of God, just and good, is that the children of earth should be happy, and enjoy every pleasure compatible with public welfare.”  Although Helvétius, true to his materialism, did not assign any intrinsic value to utility or pleasure, he thought that it is in the interest of everyone to concentrate only on those pleasures that do not present a burden for other people, unlike the pleasures of the priests and the rulers.
The psychological hedonism of Helvétius was considered an extreme case of materialist philosophy. That even his fellow materialist Diderot wrote a treatise entitled The Refutation of Helvétius, shows the controversial reputation of his work.  However, contrary to what we may expect on the basis of its title, in that treatise Diderot does not attempt to refute Helvétius’ hedonism or materialism, but focuses on criticizing his alleged failure to distinguish animal behaviour from human morality and on the claim that everyone has equal intelligence, and on various issues that are not directly connected to the most controversial aspects of Helvetius’ work, such as refuting his view that “boredom” and “idleness” are similar states.  Even in his most sustained criticism, Diderot does not challenge materialism: humans are distinct from animals not on account of having immaterial souls, but because only humans are capable of virtue. 
By “virtue” Diderot does not mean a disposition motivated by religious ideals – which not only Helvétius, but also he deems artificial – but acting in a way that brings pleasure and comfort to others.  Incidentally, this is also how Helvétius defines true, uncorrupted virtue.  Thus defined, virtue becomes conducive to the realization of public welfare. Diderot makes, however, a more concerted effort than Helvétius to show that the connection between virtue and public welfare can be preserved in a psychologically hedonist ethics that ote from their original cause.ction of various editions of Lucretius' f matter.etius, and supported so in non-religious ethicsreduceequau equates happiness with the experience of pleasure. Diderot vividly describes the pleasures that the uncorrupted virtue brings in Rameau’s Nephew, in which the narrator (Moi) defends virtue to the sceptical nephew (Lui):
I’m not against a party with my friends sometimes, a debauch, even one that gets a little out of hand. But I won’t conceal from you that it is infinitely more pleasurable (infiniment plus doux) to me to have helped someone in distress, brought some difficult business to a conclusion, given some beneficial advice, read something agreeable, taken a walk with a man or woman close to my heart, passed some instructive hours with my children, written a good page, fulfilled the duties of my position, or told the woman I love something tender and soft, so that she put her arms around my neck. I know the sorts of actions I would give up all I own to have done (Je connais telle action que je voudrais avoir faite pour tout ce que je possède). 
These conclusions of the narrator concur not only with the conclusions that Diderot presents in the Refutation,  but also with certain arguments in his other works. Virtuous acting, insofar as it brings ‘infinite’ pleasure, satisfies our natural desire to be social. But this fact can be easily lost, because virtue, as the hero Dorval observes in Diderot’s early play, Le Fils Naturel, is often incompatible with instant sensual gratification.  Elsewhere, Diderot hints that religious authorities misuse the concept of virtue by claiming that virtue is so painful that only the fear of hell can keep people away from vice.  According to Diderot, it is true that nature does not reward religious ideals such as “chastity and strict continence” with any pleasure, but this only shows that those “virtues” are artificial, devised by the priests to keep people obedient and undemanding.  As regards real virtues, those that are based on our social nature, they, claims Diderot, compensate restrictions to instant sensual gratification that they impose by providing us with a far more preferable kind of pleasure in the form of “calm”  and “internal satisfaction.” 
From the works of baron d’Holbach, one can find arguments against the religious moral teaching that are borrowed from Helvétius and Diderot. This is not surprising, given that he hosted dinners for them, and thus became acquainted with them. With Diderot they were even friends and probably collaborated in preparing texts for publication.  Helvétius and d’Holbach were acquaintances until the former’s death, a few years after which d’Holbach ceased producing new philosophical work.  It was doubtless conducive to their relationship that both occupied a similar professional context as high-ranking public servants: before dedicating themselves to philosophy and charity, the former was a fermier général, the latter a conseiller-secrétaire du roi.  Apart from his contemporary influences, d’Holbach, like both Diderot and Helvétius, was also an admirer of the ancient Epicureanism and possessed an impressive collection of various editions of Lucretius’ De Rerum Natura, twelve in total. 
In the manner of Epicureans, d’Holbach attempted to formulate a comprehensive theory of human morality on materialistic grounds.  The first part of d’Holbach’s opus magnum, Le systéme de la nature, is dedicated to presenting the flaws of religious moral teaching and his materialistic remedies to them, the second to refuting popular arguments for the existence of God. Like other materialist philosophes, also d’Holbach conceived pleasure as a transient state: “Happiness to be felt cannot be continued,” for “want is a pleasure in the moment when it is satisfied.”  Desire “is the thirst that renders the pleasure of drinking so agreeable; life is a perpetual circle of regenerated desires and wants to be satisfied.”  In the Systéme, d’Holbach took from Lucretius the thesis that superstition corrupts us and prevents us from developing virtue: “Man is wicked, not because he is born so, but because he is rendered so,” writes the baron.  The influence of Helvétius is evident in his corollary view that “man lived unhappy, because he was told that God had condemned him to misery.”  We are religious, as Helvétius had argued, and obey the priests’ conception of virtue, as long as we are not aware that it has been created by them to advance their own interests. However, this conclusion did not mean for d’Holbach that the traditional conception of virtue is artificial, as it was for Helvétius; rather, “virtue is the true, the only road to happiness.”  What makes religious teaching harmful is that it represents virtue “as the enemy to happiness.”  Following Diderot, d’Holbach claimed that the few religious virtues notwithstanding, there are also virtues that are beneficial for humans. 
The above presented views seem eclectic and therefore d’Holbach has been sometimes labelled as “unoriginal” and less interesting than the philosophes whose work influenced his thought. In the historical accounts of the Enlightenment materialism, he is often classified as a thinker who equates happiness with pleasure.  At face value, d’Holbach seems to support psychological hedonism that is similar to Diderot’s. In the Systéme he writes that happiness “is continued pleasure”  and that “those [actions] which […] tend to the permanent happiness of [human] species, are called virtues, and are necessarily pleasing to all who experience their influence.”  I think, however, that this impression is misleading. For d’Holbach was well-acquainted with the work of Diderot and thus also aware that the conception of virtue as the source of the greatest pleasure cannot address a certain sceptical challenge which a coherent materialist moral theory should be able to address.
In Diderot’s Rameau’s Nephew, the nephew comments the narrator’s defence of virtue, which I quoted earlier,  by stating that happiness caused by virtue “is a type of happiness which I will find it difficult to get familiar with, because we meet it rarely […] I observe countless decent people who are not happy, and countless people who are happy without being decent.”  The nephew’s sceptical comment urges the narrator to justify his preference of the pleasures of virtue to those of vice, given that their superiority cannot be observed. The narrator’s defense reflects only the personal conviction that he has about the “infinite” pleasure of virtue and thus it cannot convince people who do not believe in such pleasure. Although he tries to explain to the nephew that this is because most people do not know what happiness is, the nephew points out in an uncompromisingly empiricist manner that any presuppositions about the nature of happiness should be derived from empirical observation.  Eventually, their discussion concludes with the narrator’s resignation from his attempts to convince the nephew to change his views:
Lui: Farewell, Mister Philosophe. Isn’t it true that I’m always the same?
Moi: Alas, yes – unfortunately.
Lui: Well, I hope this misfortune keeps going for another forty years. The man who’ll laugh last, will laugh the best. 
In his works, Diderot does not further address this self-imposed challenge of justifying the preferability of the pleasures of virtue to vicious ones. However, I engage in showing next that d’Holbach made an effort to construct a solution to this challenge. I argue that this hitherto unacknowledged attempt led him to abandon the association of happiness with pleasure.
The reputation of baron d’Holbach as a psychological hedonist rests on the passages that have been quoted in the previous part and on the fact that as a supposedly unoriginal work, the Systéme has not attracted scholars to attempt a careful reconstruction of its arguments. Otherwise it would have been noticed that d’Holbach does not offer continued pleasure as an alternative to Diderot’s “infinite” pleasure as an explanation for the value of virtue. D’Holbach never implies that happiness is the same as continued pleasure, but only attributes such pleasure to happiness. We must also recall his conclusion that felt happiness cannot be continued.  The reasoning that led d’Holbach to this conclusion is presented immediately after the attribution. If happiness were only continued pleasure, achieving and maintaining it would require that one’s “powers were infinite,” that one could satisfy one’s desires in a constant succession.  This conclusion shows that d’Holbach regarded the states of pleasure as inherently transient in line with the Hobbesian theory that the prospect of receiving new pleasures tends to make one dissatisfied with one’s pre-existing pleasures.  This position left him with two alternative conclusions: happiness is either impossible to achieve and maintain, or happiness is not identical with continued pleasure. But d’Holbach strongly opposes the former conclusion,  and evidently thinks that happiness is in our reach:
[T]he happy man is he who knows how to enjoy the benefits of nature: in other words, he who thinks for himself; who is thankful for the good he possesses; who does not envy the welfare of others; who does not sigh after imaginary benefits always beyond his grasp. The unhappy man is he who is incapacitated to enjoy the benefits of nature; that is, he who suffers others to think for him; who neglects the true good he possesses, in a fruitless search after imaginary benefits; who vainly sighs after that which ever eludes his pursuit. 
The above passage of the Systéme paints a Rousseau-like picture of happiness, according to which happiness can be realized through self-acceptance. Although accepting oneself as one is produces pleasure, happiness is not identical to this pleasure. While pleasure is a transient aim that can never be secured, we, suggests d’Holbach, have “truly good” traits by nature, for which we should be only thankful to achieve happiness. These truly good traits consist of other-regarding virtues such as “humanity,” “benevolence,” “compassion,” and “equity.”  For “it is man who is most necessary to the welfare of man.”  The conception that pleasure could suffice to make a human being happy is elusive, because “pleasure is but a momentary happiness, which frequently becomes an evil”  – i.e., whenever it becomes our primary aim, replacing the cultivation of other-regarding virtues. 
We fall into this psychological trap as a result of being told by the priests that happiness is so “distant” that there is no way for us to achieve it in this world, even if we abstained from all pleasures – which makes us demotivated to pursue anything but the sensations of pleasure.  Only the understanding that happiness is neither inconceivably distant nor identical to pleasure, but – as d’Holbach concludes – “the accord which is found between oneself and those circumstances in which he has been placed by nature,” could change this self-destructive course. 
However, d’Holbach’s Rousseau-like description of happiness is not yet his final definition of it. This conception would not survive from the sceptical challenge of Rameau’s Nephew, since whether or not one has “found the accord with nature” seems a matter of subjective perception rather than empirical observation. Thus, in order to meet the challenge, d’Holbach needs to reduce happiness to an empirically observable state which results from living in accordance with nature. In the Systéme, he suggests that self-acceptance and other-regarding virtue are conducive to a long life, while the pursuit of pleasures often shortens one’s life: “be happy in that existence which is known to you; if you would preserve yourself, be temperate, moderate, and reasonable; if you seek to render your existence durable, do not be prodigal of pleasure.”  This claim opens a possibility that happiness, realizable through self-acceptance and virtue, could be definable as self- -preservation – a definition that would be both empirically verifiable and not commit the baron to psychological hedonism.
Apart from dedicating sections in the first part of the Systéme to constructing a materialist conception of happiness, also in his later treatise, titled Elements de la morale universelle, d’Holbach focuses on the same topic. Incidentally, this treatise is also his last philosophical work. In the Elements, d’Holbach describes happiness as “the duration or the continuation of the pleasures and states that are favourable to man.”  This may easily seem to be a definition along the psychologically hedonist lines, but a more careful reading reveals that apart from the continuation of pleasure, also the “favourable states,” or other-regarding virtues, matter to happiness. Instead of being motivated by a prospect of pleasure, the other-regarding virtues are grounded in the “duty of humanity,” by which the baron refers to our natural disposition to help other human beings.  Since we know from the Systéme that continuous pleasure is impossible to achieve and maintain, the other-regarding virtues must be more central to happiness than pleasure. D’Holbach confirms this by writing that those virtues “preserve a man, maintain him in a way of being that he loves and whose continuation he desires,”  and that “pleasure is good only insofar as it preserves man and maintains him in an orderly state.”  By emphasising the centrality of the other-regarding virtue to happiness on account of their favourable contribution to one’s self-preservation, and by making the value of both virtue and pleasure conditional upon this contribution, d’Holbach implies that happiness consists essentially in self-preservation.
The observable fear that people feel when facing a sudden danger, the effort that many put in prolonging their lives, and even the fact that the human population on earth is on the trajectory of growth, can provide the needed empirical evidence for showing that, as a species, we prefer self-preservation over self-destruction. Therefore, provided that baron d’Holbach regarded happiness as self-preservation, as his claims imply, his conclusions about the nature of virtue and happiness could be in principle compatible with his materialism and also respond to the sceptical challenge presented in Rameu’s Nephew. But the identification of happiness with self-preservation would not yet clear the baron from the charges of unoriginality, because this idea is indebted to the thought of Spinoza. I attempt to show, however, that the use that the baron made of this conclusion in his struggle against religion constitutes an original philosophical move.
Possibly, since “Spinozism” had such notorious reputation among the general public in the 18 th century, d’Holbach remained rather silent about his acquaintance with Spinoza. However, also Spinoza maintained that our essential pursuit (conatus) is that of self-preservation.  And just as d’Holbach claimed that virtues that contribute to self-preservation are pleasant – although vices can be more pleasant – so Spinoza stated that activities helping mind to achieve “greater perfection” produce pleasure, though pleasure lacks any intrinsic value.  But while Spinoza considered religious teaching helpful to the rulers who want to keep ignorant people in check, and bring stability to the state,  d’Holbach diagnosed it as keeping people ignorant of reality. Instead of helping us to understand the human nature, religion teaches us to fear such understanding. 
According to d’Holbach, the reason why so many people are religious is that religion promises eternal life to obedient believers. Thus, it appeals to the desire that constitutes our essence, the fulfilling of which our happiness consists in. However, the religious doctrines that priests ask us to observe in order to manifest our obedience were, according to d’Holbach, devised only to manipulate our minds – to make us believe that the eternal bliss in heaven is reserved only for those who obey the priests, and eternal damnation for those that question their authority – so that we would be easily manageable subjects for rulers, whose interests the priests work to advance. 
Ignorance upheld by religion is harmful for people, because contrary to the promises of the priests, religious observance cannot satisfy the desire of happiness – unlike a virtuous concern for others, which presupposes the knowledge of human nature. According to d’Holbach, there is no eternal life in heaven; the best we can hope for is to flourish on earth. If the promise of the religion really satisfied our desire of happiness, the baron argued, religious people would not fear physical death. However, even the most religious people are, d’Holbach observed, afraid of death, which shows that their religion has failed to give them happiness.  But if we understood that happiness is reachable by human effort – the kind of understanding that the religion wants to prevent us from acquiring – that being helpful to others, which is also pleasant, and shunning the painful and solitary religious “virtues” is the safest bet for preserving oneself over time (because by nature people tend to reciprocate the help they receive), the religion would lose its motivational force upon us. D’Holbach is convinced that, upon acquiring such understanding, we would perceive the self-interested character of the religious moral teaching which is based on vain hope and false dualism between pleasure and happiness. Since one’s degree of understanding of the human nature thus conditions one’s moral motivation, d’Holbach considers it necessary for the moral progress of humankind that the religious teaching be replaced with enlightened education along the lines of the Encyclopedie. Near the end of the first part of the Systéme, the baron proclaims:
Man will ever mistake his true happiness as long as he neglects to study nature, to investigate her laws, to seek in her alone the remedies for those evils which are the consequence of his errors: he will be an enigma to himself, as long as he shall believe himself double; that he is moved by an inconceivable spiritual power, of the laws and nature of which he is ignorant. 
In this article, my aim was to show that d’Holbach is a more interesting materialist critic of religious moral teaching than it is often thought, that he makes an original contribution which avoids certain problematic aspects of the arguments offered by his fellow materialist philosophes, Helvétius and Diderot. The common ground between them and d’Holbach was the view that happiness is the end of all human desire and that the religious moral teaching makes a mistake in presenting happiness as a purely transcendent aim. By emphasising that virtue requires sacrificing earthly pleasures, this teaching makes virtue into the antithesis of what is commonly perceived as a good life. All the three materialist philosophes were inspired by empiricist science in arguing that pleasure must be the central part of our happiness, but the arguments against the religious conception of happiness that they made on the basis of this commitment differed. Helvétius argued that traditional virtue is artificial, created to advance the interests of the priests at the cost of everyone else’s interests, and only pleasure truly motivates us. However, this approach amounted to the rejection of the entire traditional conception of virtue in response to the inclusion of self-sacrificing behaviour among virtues by the priests. Thus, Diderot chose a different argumentative strategy. He wanted to show that a few exclusively religious virtues notwithstanding, pleasure and virtue are in fact compatible, even dependant on one another. For Diderot, true virtue boils down to helping others – not by praying, but by acting. He suggested that being good to others can produce pleasure that is inherently preferable to all other pleasures. However, Diderot also recognised that the preference of one pleasure over another is a personal experience that cannot be generalised on the basis of empirical observation. It seems, after all, that many vicious people are happy with their lives. Diderot did not further address this issue. However, d’Holbach was aware that a coherent materialist moral system, the building of which was his ambition, should be able to empirically justify the preferability of helping others to ignoring or harming them. To construct the needed justification, d’Holbach disconnected psychological hedonism from materialism. According to him, the preferability of virtue does not derive from the pleasure that it may produce, but from the fact that virtue is the safest bet for preserving oneself. As Spinoza posited, the desire of self-preservation is our most basic desire, and therefore d’Holbach deduced that satisfying it must be the essence of happiness. A vicious person can perhaps enjoy more than a virtuous person, but his existence is more precarious. This is a justifiable reason for a materialist to eschew psychological hedonism.