Start Submission Become a Reviewer

Reading: Virtual Union, the Seeds of Hatred, and the Fraternal Joining of Hands: Leibniz and Toleration


A- A+
Alt. Display


Virtual Union, the Seeds of Hatred, and the Fraternal Joining of Hands: Leibniz and Toleration


Mogens Laerke

X close


In this paper, I am interested in the conception of toleration that can be gleaned from the political and theological texts of Gottfried Wilhelm Leibniz. I argue that Leibniz did not defend a notion of toleration comparable to a standard modern conception. The modern conception is very often traced back to a constellation of writers contemporary with Leibniz including Locke, Bayle, and Spinoza. It involves an inclusive embrace of diversity, religious and otherwise, and an affirmation of toleration as a fundamental value in and by itself, intrinsically linked to an equally fundamental imperative of freedom of expression allowing such diversity to flourish publicly. Leibniz, however, understood toleration as a political tool to be employed in order to facilitate the reunion of the Christian churches; he did not consider it a constitutive value, or a value in and by itself, but rather saw it as a means to an end; he did not establish any intrinsic link between toleration and freedom of expression but promoted moderate forms of censorship. Most importantly, however, while clearly seeing it as something positive, he also detected deep ambiguities in the concept from which we have much to learn in our own assessment of modern toleration.
How to Cite: Laerke, M., 2019. Virtual Union, the Seeds of Hatred, and the Fraternal Joining of Hands: Leibniz and Toleration. Journal of Modern Philosophy, 1(1), p.6. DOI:
  Published on 17 Jun 2019
 Accepted on 01 Apr 2019            Submitted on 06 Dec 2018

1. Introduction

In this paper,1 I am interested in the conception of toleration that can be gleaned from the political and theological work of Gottfried Wilhelm Leibniz (1646–1716). Contrary to many previous commentators, I argue that Leibniz did not defend a notion of toleration comparable to a modern conception. Certainly, the term ‘toleration’ figures in his writings.2 It even figures quite frequently in certain contexts, and most often as something positive. But his explicit conception of toleration was not forward-looking but rather shaped by a long past of post-Reformation religious wars and European theological-political turmoil.3 When speaking of toleration, Leibniz mostly looked backward in time, to figures like Georg Calixtus, his favorite theologian, and to texts like De tolerantia reformatorum where Calixtus had shown, in Leibniz’s words, that ‘even though there is divisive opinion, that should never prevent jungi dextras fraternitatis.’4 Leibniz’s aim with promoting such ‘fraternal joining of hands’ was principally securing peace and providing better prospects for future religious conciliation, not defending the kind of liberal embrace of religious pluralism and freedom of expression associated with toleration today.

And yet Leibniz is often presented as a champion of modern toleration on a par with Locke or Bayle.5 For a striking example, one can read the following in an introduction by John Christian Laursen to a volume on seventeenth-century theories of toleration: ‘The strongest legacy to toleration theory of the Thirty Years’ War may well have been in the writings of Gottfried Wilhelm Leibniz, who wrote at the end of the seventeenth and beginning of the eighteenth centuries, and pushed toleration theory well beyond anything Locke or Bayle could manage’ (Laursen 1998: 171). Others have made similar claims. Franklin Perkins writes that ‘Leibniz worked tirelessly to promote tolerance, peace, and the exchange of ideas, perhaps most in his attempts to bridge religious factions in Europe, but also in his receptiveness to the past and his attitude toward other cultures’ (Perkins 2002: 447). Maria Rosa Antognazza has dedicated several articles to the topic, currently the most sophisticated and extensive contributions to the discussion, where she argues that ‘a robust, many-layered, and unusually inclusive doctrine of toleration can be gleaned from Leibniz’s writings.’6

There is an obvious, literal sense in which such statements are problematic.7 They do not correspond to Leibniz’s explicit and most consistent use of the term ‘toleration’ which, as we shall see below, almost invariably occurs in the context of discussions about ecclesiastical toleration and church reunion, as part of an approach to religious diversity that remains subordinated to his irenical quest for reunion. There is however another sense in which one might say that Leibniz promoted toleration, namely if, within the framework of working toward Christian reconciliation (including the rational outreach to other religions that his conception of natural religion allowed, as can be seen in his writings on China for instance), he provided a conceptual framework that potentially, when rising above the consideration of the particular circumstances and explicit purpose of that framework, is comparable to a modern theory of toleration. Among commentators who have championed Leibniz as a thinker of toleration, this is the approach they most frequently adopt, less concerned with terminology, occurrences and specific contexts of use, than with the general theory lurking behind individual statements and the basic ethical commitments channeled by this theory. This is for example the perspective that Maria Rosa Antognazza adopts in her insightful contributions.

While I am wary of letting entirely go of the more literal and lexical issues, I think this is a fruitful approach. I will however argue below that, even when doing that, we will still not be able to dispel the clouds of doubt hanging over Leibniz’s credentials as a thinker of ‘modern’ toleration. For even on this less literal approach to the question, associating Leibniz with the doctrinal constellation which, in the late seventeenth and early eighteenth centuries, arguably provided the first outline of what is today considered toleration in the modern sense, remains problematic because it fails to take into account, not only the kind of theory that Leibniz did in fact promote, but also tends to gloss over the specificity of the modern notion of toleration that commentators are saddling him with. Thus, as I will argue below, Leibniz’s conception of toleration differed from the modern conception in the following three ways:

  1. Literally, Leibniz understood ‘toleration’ in a narrow sense, as a political tool to be employed in order to facilitate the reunion of the Christian churches. It was not understood as a broad embrace of diversity in religious matters. In its two basic forms, civic and ecclesiastical toleration, it was a means to lay down the fundamental conditions—peace and security on the one hand; acknowledgment of people with differing religious views as legitimate discussion partners, on the other—for any possible negotiation toward future church reunion. In short, the two forms of toleration were designed specifically to end violence and to multilaterally suspend mutual accusations of heresy.
  2. While Leibniz did promote toleration in some sense, and also did adopt some of the fundamental ethical tenets habitually associated with a modern conception of toleration, he did not consider toleration a constitutive value, a value in and by itself, but rather saw it as a means to an end, namely, as already said, the conciliation of the churches and the end of schism. On the more abstract level, one might say that Leibniz did not promote modern toleration because modern toleration is about affirming diversity as a value in and by itself, not about using such an affirmation to eventually cancel difference and work toward union.
  3. Leibniz did not establish any intrinsic link between toleration and freedom of expression, and even argued that toleration, in the sense in which he promoted it, would require that licentious speech and writing be curbed and a regime of (moderate) censorship put into place.8

2. The Construction of Modern Toleration: Locke, Bayle, Spinoza

Before embarking upon any discussion of Leibniz and toleration it is crucial to establish a point of reference. What kind of doctrine is it, exactly, we attribute to Leibniz if we situate him among the first champions of modern toleration? One could for example consider toleration to mean principally a resistance to religious coercion, opposition to the use of force to thwart opinions and persecution in matters of conscience. If that is what toleration is, Leibniz was, as Maria Rosa Antognazza argues persuasively, a firm and unequivocal proponent. The textual evidence is overwhelming but a few examples will suffice. In 1692, the French cleric Paul Pellisson-Fontanier published his epistolary exchanges with Leibniz under the title De la tolérance des religions (Pellisson-Fontanier 1692). The exchange was presented by Pellisson as a discussion on ‘the unity of the church, and on the question whether it should tolerate sects’ (Pellisson-Fontanier 1692: 3). In it, Leibniz developed an argument against persecution of confessions and sects considered heretical by insisting on the involuntary character of belief.9 As also in his correspondence with the intransigent Bishop Bossuet, Leibniz insisted on a distinction between material and formal heresy, arguing that only formal heresy, i.e. intentional error or obstinacy, gave sufficient grounds for blame and excommunication. Citing the involuntariness of belief, Leibniz also denied the very possibility of genuinely renouncing upon truths one sincerely believes to possess, for example for a natural philosopher to genuinely disavow his own scientific knowledge on account of a perceived conflict with church doctrine:

To believe or not to believe is not a voluntary thing. If I believe I see a manifest error, all the authority of the world could not change my view if this [authority] is not accompanied by some reasons capable of satisfying my difficulties or of overcoming them. And if the whole Church were to condemn the doctrine of the movement of the Earth, the able astronomers of this opinion could certainly dissimulate, but it would not be in their power to give up [their view].10

Hence, on this definition of toleration, as a principled resistance to the coercion of beliefs, Leibniz was undoubtedly a champion of toleration. This, however, as we shall see below, was not Leibniz’s own definition of toleration. Moreover, and more importantly, it is not clear that, more broadly, it is a satisfactory and sufficient characterization of the modern conception of toleration either. Certainly, it is a part of such a conception. Good reasons exist, however, to think that there are further requirements to fulfill. It is for this reason that a clearer point of reference must be established.

In the following sections, I will try to situate Leibniz in relation to three contemporaries who were among the most prominent proponents of toleration, namely Locke, Bayle and Spinoza. Let me be clear from the outset that the following outlines are not intended as full-fledged accounts of the doctrines of toleration of those three authors, an ambition obviously far beyond the scope of this paper. What I am interested in is how the reference to those three authors’ basic conceptions of toleration are constantly taken up by historians of philosophy when accounting for the contributions of late seventeenth-century philosophers to what they often describe as a modern or contemporary notion of toleration. I neither embrace nor reject those accounts. I am only interested in how they have contributed to a common notion of modern toleration and its seventeenth-century background in present-day commentary which explains what is generally meant when historians of philosophy ascribe a doctrine of ‘modern toleration’ to this or that thinker. Certainly, the conceptions of toleration that can be gleaned from Locke, Bayle, or Spinoza are not the only conceptions available for conceiving of such a notion of toleration. And I do not deny that Leibniz may be situated differently in the intellectual landscape if we evaluate his position according to other, competing conceptions, both earlier and later, like those of, say, Sebastian Castellio,11 Gotthold Ephraim Lessing,12 or John Stuart Mill.13 Nonetheless, I have chosen Locke, Bayle and Spinoza as providing a useful and non-anachronistic point of reference, because those three figures are frequently, and in very influential historical commentaries like those of Perez Zagorin, Jonathan Israel, Philip Milton, or Rainer Forst, taken to be paradigmatic early modern thinkers of toleration.14

At the same time, these three philosophers cannot be said to promote the same aspects of toleration or even be seen as consciously contributing to a common conception. In fact, in the late seventeenth century, toleration was by no means a well-defined intellectual rallying-point, but rather a shared component in a family of related doctrines, some of which explicitly promoted toleration under that name, while others might not necessarily have used the term but still advanced arguments that contributed to the constitution of the meaning of it. Some ‘doctrines of toleration’ were even only described as such pejoratively, as implying an accusation of religious laxity and a license to heresy.15 It is however not unreasonable to maintain that Locke, Bayle and Spinoza were, in different ways, among the most prominent members of that sprawling family and that, consequently, as Rainer Forst puts it, ‘the modern discourse concerning toleration … reached its political-philosophical culmination in the works of Spinoza, Locke and Bayle’ (Forst 2013: 170).

One way, then, of getting a better grip on how Leibniz stands precisely with regard to the question of modern toleration is thus through a kind of doctrinal triangulation, trying to determine how Leibniz was philosophically situated with regard to each of them and what they have come to represent, taking into account the similarities and differences in their respective theoretical models that both gather them and set them apart as members of same family. It is those basic similarities and differences between Locke, Bayle and Spinoza that I will sketch out in this section. In short, I will give a basic portrait—some would say a caricature, but I think it useful for the present purposes—of how these three philosophers have been constructed by contemporary intellectual historiography as the paradigmatic thinkers of early modern toleration without pretending in any way to provide an exhaustive account of their respective theories, or accounting for the philosophical and historical relations obtaining between them.16

2.1. John Locke

Locke’s notion of toleration in his Letter Concerning Toleration (1689) is a theological notion more than it is a political one: ‘[T]oleration [is] the chief characteristic mark of the true church’ (LCT 7). His argument stresses the primacy of internal belief over religious institutions (LCT 17). He rejected the ‘external pomp and ecclesiastical dominion’ while understanding ‘true religion’ as ‘the regulating of men’s lives, according to the rules of virtue and piety’ (LCT 7). Locke, of course, was not the first to make such arguments. He owed much to the humanist tradition, for example. Contrary to many predecessors, however, most of whom saw toleration as part of a strategy to reunite or diminish divergence between confessions, and also contrary to the latitudinarianism embraced by Anglican divines who saw toleration as an exercise of Christian love in spite of diversity of opinion,17 Locke did not—or at least not always—argue in view of cancelling ‘the divisions that are amongst sects.’ Instead, he provided the first conceptual components toward genuine pluralism, that is to say, toward a genuine embrace of such ‘divisions’ as politically manageable and theologically legitimate.18 Hence, Locke, in his most radical moments, suggested that we not only endure but affirm differences for the sake of salvation:

The toleration of those that differ from others in matters of religion, is so agreeable to the Gospel of Jesus Christ, and to the genuine reason of mankind, that it seems monstrous for men to be so blind [as not to perceive the necessity and advantage of it] in so clear a light. (LCT 15)19

On this picture, religious diversity channels the values of Christianity, by providing the necessary conditions under which the kind of deep charity the Gospel calls for—namely, loving one’s enemy and not just one’s neighbor—can be exercised.20 As he wrote to Limborch in September 1689: ‘Men will always differ on religious questions and rival parties will continue to quarrel and wage war on each other unless the establishment of equal liberty for all provides a bond of mutual charity by which all may be brought together into one body.’21

Admittedly, globally, Locke’s work on toleration was not quite the kind of celebration of plurality later found in John Stuart Mill’s On Liberty (1859). And yet Locke’s argument, and the way it was received in the High Enlightenment, played a crucial role in making toleration a constitutive value (i.e. a value in and by itself rather than something to be embraced in view of some other value, like peace or salvation) by making the embrace of difference rather than the will to unity basic for the ethical and religious attitude he designated as ‘true religion.’ Moreover, he formulated fundamental principles of non-interference in religious matters on the part of the civil magistrate, predicated on the idea that inner convictions are shielded against coercion (LCT 19). Finally, by considering religious congregations as ‘private persons’ in the eyes of the law, Locke employed this same principle to argue in favor of separating State and Church (LCT 3 and 39).

At the same time, Locke’s toleration was also notoriously restrictive in scope as a result of additional political considerations: Roman Catholics were excluded not for their specific beliefs or articles of faith, but because they pay allegiance to a foreign power, the Pope; atheists were excluded because there is nothing to hold them to their oaths, rendering social bonds void; ‘Mahometans’ were excluded on account of their alleged ‘blind obedience to the Grand Mufti of Constantinople’ (LCT 79, 91, and 93).

2.2. Pierre Bayle

Pierre Bayle’s contribution to the emergence of modern toleration is mainly associated with two texts: the Pensées diverses sur la comète (1682)22 and the Commentaire philosophique sur les paroles du Jésus-Christ, Contrains-les d’entrer (1686).23 In the Pensées diverses, Bayle famously argued in favor of the possibility of a society of atheists, often denied on the grounds that the oath of an atheist cannot be trusted, excluding them from contracting any valid social bond. Bayle argued to the contrary that the practical virtues binding civil society together were independent of religion, but grounded in moral conscience and right reason. For Bayle, it was perfectly possible to both reject the Christian faith and act morally. Bringing empirical evidence to bear on the topic, he noted how history had produced vicious Christians as well as virtuous atheists. As he puts it in the ‘Éclaircissement sur les athées’ added to the 1702 edition of his Dictionnaire historique et critique, ‘the greatest scoundrels are not atheists at all, and … most of the atheists whose names have been handed down to us were honorable people’ (Bayle 1820: XV.277). In fact, the veritable ‘scandal’ was not the existence of people without religion, but on the contrary that there were ‘so many people both convinced of the truths of religion and fallen into crime’ (Bayle 1820: XV.273). Bayle’s argument extended the conceptualization of toleration beyond the sphere of religious discourse, grasping it as a secular virtue. In the Commentaire philosophique, a long political pamphlet written in response to the nasty religious politics of Louis XIV and in particular the Revocation of the Nantes Edict in 1685, Bayle made himself a proponent of what his Calvinist arch-enemy, Pierre Jurieu, denounced as horrible ‘universal toleration’24—a characterization of Bayle’s position which later readers also adopted but now to praise him, most famously Voltaire in his 1763 Traité de la tolérance.25 Bayle argued against the Augustinian notion that forced conversions can be justified as a means of saving souls, supported by the biblical parable of the great banquet, where the host asks his servant to ‘Go out to the roads and country lanes and compel them to come in’ (Luke 14:15–24). By opposing the compelle intrare argument, Bayle blocked an argumentative strategy that, perversely, had justified religious persecution in the name of Christian charity. By the same token, however, he also contributed to the understanding of toleration as a constitutive value, an end in itself, by operating a reversal in the order of priority between toleration and the cardinal virtue of Christian charity, making the former a condition of the latter and thus in a sense more fundamental.

In this context as well, a conception of a fundamental moral conscience, separate from religion but grounded in reason and human nature, played an essential role. Bayle’s aim was to entirely dissociate toleration from religion and refer it to a form of moral rationalism, a basic duty to follow the dictates of conscience: ‘I don’t believe any one will contest the Truth of this Principle, Whatever is done against the Dictates of Conscience is Sin’ and ‘the first and most indispensable of all our Obligations, is that of never acting against the Instincts of Conscience’ (Bayle 2005: 220 and 227). At the same time, however, slippery as always in his argumentation, Bayle also defended the rights of the ‘erroneous conscience’, indeed held that the duty to act according to what was dictated by one’s conscience held regardless of whether one’s conscience was in the right, potentially displacing the criterion of the tolerable from the question of true moral conscience to that of a merely sincere one.

2.3. Baruch Spinoza

Contrary to Locke and Bayle, Spinoza did not, strictly speaking, have a notion of toleration. The term figures only once in his entire work, in Latin in chapter XX of the Tractatus theologico-politicus, in a context where it is most appropriately translated ‘endurance’ (G III.245/C II.350). And yet, as we have seen, he frequently figures among the first promoters of a modern notion of toleration.26 The implicit justification for including Spinoza in this group is, of course, that it matters little if the term is present if only the idea is. And there certainly are aspects of Spinoza’s political, theological and ethical thinking, in the Tractatus theologico-politicus in particular, that clearly, almost intuitively, resonate with a modern understanding of toleration. Most important is, I think, the way in which Spinoza tied toleration—or rather the kind of virtues we today associate with toleration—to freedom of conscience and expression, and to what he called ‘freedom of philosophizing’ in chapter XX of the Tractatus. Hence, Spinoza argued, those who ‘try to take this freedom away from men’ will seek to ‘bring to judgment the opinions of those who disagree with them’ (G III.247/C II.353), and proclaimed that those who ‘censure publicly those who disagree’ and ‘persecute in a hostile spirit’ are ‘the worst men’ (G III.8–9/C II.70–71), even the ‘Antichrists’ (G III.176/C II.267). The specificity of Spinoza’s defense of the ‘freedom of philosophizing’ also resided in his attempt to show that such freedom was not simply permissible or not harmful to the state, but on the contrary the very condition of peace and stability. As Spinoza puts it, he wanted to show ‘that the republic can grant freedom of philosophizing without harming its peace or piety, and cannot deny it without destroying its peace and piety’ (G III.3/C II.65). As we shall see below, what Spinoza understood by ‘freedom of philosophizing’ is complicated by the republican background of his political philosophy, in the final analysis more focused on virtues and civic duties than on individual liberties, and by his philosophical conception of freedom built up around a largely Stoic conception of rational self-determination. Nonetheless, putting to one side these complexities which continue to divide commentators, it is agreed that, whatever freedom of philosophizing means more precisely, the conception is accompanied by a conception of peaceful co-existence which, if not in name then in spirit, amounts to something like a doctrine of toleration which is embedded within a political philosophy stressing that ‘men must be so governed that they can openly hold different and contrary opinions, and still live in harmony’ (G III.247/C II.353). It is an ideal perhaps best described in the portrait—sincere or ironic, no matter—that Spinoza gives of the city of Amsterdam and the Dutch republic: ‘In this most flourishing Republic, this most outstanding city, all men, no matter what their nation or sect, live in the greatest harmony.… Provided they harm no one, give each person his due, and live honestly, there is absolutely no sect so hated that its followers are not protected by the public authority of the magistrates and their forces’ (G III.246/C II.351–52).

In sum, when combining the respective contributions of Locke, Bayle, and Spinoza to the constitution of what Forst described as ‘the modern discourse concerning toleration’, and putting to one side questions of detailed argument, chronology and the historical play of influences, focusing solely on the basic conceptual construction of the notion that can be extracted from them, one might say the following: Locke provided a basic formulation of modern toleration as a constitutive principle. Rather than considering schism the original evil and religious unity as something to be strived for necessarily, he proposed an argument which, potentially at least, made religious plurality a condition for the exercise of true religion and toleration a value the expression of which required religious diversity, albeit with restrictions that invariably bore on the effect that religious affiliation had on political allegiance. Bayle, for his part, expanded the scope of the notion to include also atheists and contributed substantially to making toleration a constitutive moral value, rather than a means to an end. Finally, Spinoza made the case for associating toleration with freedom of expression and making it not only permissible, but obligatory within a free republic and conducive to civil stability. When putting these elements together, there emerges a conceptual configuration in which we recognize a liberal understanding of the benefits of plurality, closely related to another, equally constitutive value, namely freedom of expression. The question is how Leibniz’s conception of toleration maps on to this complex modern notion of toleration.

3. Leibniz on civil and ecclesiastical toleration

For Leibniz, toleration was mainly construed as a necessary condition for church reunion. Hence, he noted already in March 1683 in a letter to Ernst von Hessen-Rheinfels: ‘I admit that the powers would have to first agree to mutual toleration in order to temper the spirits, before a reunion can be hoped for’ (A I.iv.352). Toleration was sometimes associated with Leibnizian core intellectual values such as charity, good intentions, and moderation.27 But he also at times seemed to remain deliberately vague about his position on the topic, especially when writing to Catholic correspondents likely to speak of ‘toleration’ as a vice rather than a virtue: ‘I dare not myself say anything ascertained about toleration …. God knows what is right, as for me, I content myself with leaving the judgement to him, and I dare condemn only those who lack good will’ (to Paul Pelisson-Fontanier, 21 November (1 December) 1692, A I.viii.201).

He did, however, also have a more fine-grained conception of toleration, mainly inspired by the Bishop Molanus, one of his main interlocutors in a court-mandated project of reuniting the protestant churches between Hanover and Berlin that Leibniz orchestrated. It is a technical concept that is part of a three-stage model for reunion that Leibniz presented as follows in a 1697 letter to James Cresset, the English ambassador to the Berlin Court:

I note that this union can have different degrees which are (1) good public understanding; (2) ecclesiastical toleration; (3) agreement of opinions. The first and second degrees appear to me necessary, feasible, and sufficient. The first degree is necessary by political reasons for the conservation of the two parties. The second degree is necessary by the principle of Christian charity, and consequently it is more than just feasible. The third degree does not seem achievable, but is also not necessary. It would however be good if able theologians would work upon it at least in relation to certain points where I actually think that the disputes only arise on account of formulations and are not real. This conciliation of some controversies, albeit particular and imperfect, would already be of great use. Est aliquid prodire tenus, si non datur ultra [It is something to get this far, if we cannot go further]. But putting to one side the third degree, let us stick to the first and second for now.28

This three-stage model shows up on several occasions.29 In some writings, he formulates the distinction between civil understanding and ecclesiastical toleration as a distinction between civil and ecclesiastical toleration.30

Civil toleration is a matter of securing public order within the state and assuring that pacts among states are respected. As favorable as Leibniz was to civil toleration, essential to public security and the good of mankind, still, as he noted to Jablonski, ‘toleration in the public exercise of protestant religions’ belongs among the ‘affairs that do not concern the very essence of religion, but rather exterior aspects mixed up with a host of secondary considerations, political and other’ (to Jablonski, 18 December 1707, in Jablonski and Leibniz 1899: 121). In short, civil toleration is a matter of public policy more than of public morality and religion. It can be established in a state by sovereign command and upheld by executive power.31

Ecclesiastical toleration is a more complex matter. Leibniz sometimes defines ecclesiastical toleration as ‘not considering another doctrine as condemnable’ and ‘not mistaken’, as opposed to civil toleration which consists only in ‘leaving the other his freedom’ or upholding ‘civic peace’; it is a practical attitude, a ‘sincere disposition’ (Geschwinde Anmerckungen, before 12 February 1700, A IV.viii.363–64). In religious matters, such toleration is partly achieved by downplaying non-essential differences, leaving to one side what is traditionally described as ‘things indifferent’ (adiaphora)32 or at least by ascertaining that they pose no practical obstacle to reconciliation.33 Importantly, Leibniz relates ecclesiastical toleration to the principle of charity. This principle stands absolutely central in his ethics, natural theology, political philosophy and universal jurisprudence. It is a basic component in his concept of justice (defined as caritas sapientis) and is associated with formal principles such as equity, reciprocity, geometrical proportionality, harmony, and the just mean (Lærke 2008[a]: 223–6). Charity is also a principle of controversy and negotiation that Leibniz associates with a procedure of constant and complex exchanges of perspective among opposing parties, an obligation of ‘putting ourselves in the other’s place’ (Analyse de Jean Domat, end 1695, Grua 648). The conception has its background in Leibniz’s reading of the so-called ‘golden rule’ from the Gospels, i.e., the rule according to which I should not do unto others, what I do not wish others do unto me: ‘The true meaning of the rule is that the right way to judge equitably is to adopt the viewpoint of the other [la place d’autrui].’34 Leibniz’s controversialist conception of charity and the golden rule has been explored by a great number of commentators, including myself, in commentaries dedicated to Leibniz’s ‘art of controversies’, in Marcelo Dascal’s expression.35 Leibniz’s best explanation of what such charity or moderation in controversy implies in practice is probably the following, largely self-explanatory passage from his Conversation du Marquis de Pianese et du Pere Emery Eremite, written around 1679–81:

[T]his is what gives rise to this diversity of opinion, everybody considering the objects from a certain side: only very few people have the patience to go all the way round the thing [faire le tour de la chose] until they are on the side of their opponent, that is to say, people who will examine the pros and cons with equal zeal and with the spirit of a disinterested judge in order to see to which side the balance must lean. (A VI.iv.2250, translated in Leibniz 2005: 173)

As for the third degree, complete agreement, as we have seen, Leibniz sometimes concedes that ‘it does not seem achievable, but is also not necessary.’He does, however, always maintain the concept, at a minimum as a kind of regulative idea providing an ideal horizon for ecclesiastical toleration.36 The border between ‘union’ understood as an achievable goal and ‘union’ understood as a regulative idea is fluid and changes according to context. It is from this perspective that we must read the following clarification regarding the meaning and scope of ecclesiastical toleration that we find in the 1698 Tentamen expositionis irenicae trium potissimarum inter protestantes controversia:

Thus, since it is clear that the obstacles to a perfect agreement reduce to certain formulations and certain metaphysical positions, or at the most to a very limited number of controversies that concern neither the salutary faith nor practice, and which, for the rest, resemble those that frequently take place between members of the same church; and since it is clear, on the other hand, that what until now has been taken for a disagreement of the utmost importance will largely dissolve by means of such explications, once these [two points] have been admitted, nothing remains that would prevent reaching complete reunion and re-establishing an actual communion between the evangelicals and the reformed—and nothing can appear more salutary or more necessary for the Church of our time, since the virtual union or simple ecclesiastical toleration [virtualis unio sive simplex tolerantia Ecclesiastia], even though one abstains from anathema and accusations of heresy, still lets the schism and the hatred subsist, or at least the seeds of hatred [odiorum semina], and would, in the future, be exposed to constant recriminations, suspicions and conflicts. (A IV.vii.387/Jablonski and Leibniz 2013: 826–27)37

Contrary to what is sometimes suggested, I do not think Leibniz’s talk of ‘complete reunion’ in this text is at odds with other texts where such complete reconciliation is presented as something out of reach.38 The specific context of the Tentamen here plays a role: the text was part of Leibniz’s efforts to establish a reunion only among the protestant churches of Brandenburg (reformed or Calvinist) and Hanover (evangelical or Lutheran). And he was quite clear that, whenever he was speaking of complete reunion as an achievable goal, he was aiming only at a restricted one, limited to those protestant churches whose dogmatic divergences, according to him, could be resolved by simple analysis and explication of the terms of debate, in other words, by analytic resolution of pseudo-divergences.39 In this respect, one cannot consider the Tentamen to teach a general lesson about Leibniz’s views on the prospects of religious reconciliation more broadly.

The passage does, however, afford us crucial, additional lessons about the second degree in the three-stage reunion project, namely ecclesiastical toleration. Leibniz describes ecclesiastical toleration as a ‘virtual union’ as opposed to ‘actual union.’ The formulation suggests that it should be conceived as tending toward union without however itself being such a union: ecclesiastical tolerance is virtual union because it can lead to actual union.40 This positive tendency, I think, must be explained in terms of the conception of charity that Leibniz associated with ecclesiastical toleration in the letter to Cresset or, more specifically, in terms of Leibniz’s procedural and controversialist conception of charity as an exercise in reciprocity. In exchanging with others, being charitable consists in putting oneself in the others’ place and consider the point under discussion from ‘all sides.’ In this dialectical context, then, charity does not prescribe that one discusses the matter at hand in a disinterested way, but rather that one discusses it while making an active effort to take into account in an equitable and balanced fashion all the different interests involved. Being ecclesiastically tolerant is honoring that Christian duty in ecclesiastical negotiation.

And yet, at the same time, from the passage in the Tentamen cited above, it appears that ecclesiastical toleration also envelops a necessary reference to ‘schism’ and, along with it, what Leibniz describes as ‘seeds of hatred.’ This is not because the practice of ecclesiastical toleration as such involves hatred, of course, but because ecclesiastical toleration, if seen as a goal in and of itself, as opposed to a means to reach a higher goal of actual unity, necessarily implies the affirmation that such differences in perspective subsist which are at the root of schism and hatred. Practicing ecclesiastical toleration, i.e. performing one’s Christian duty to put oneself in the others’ place, necessarily involves acknowledging that others occupy places—or theological positions—different from one’s own. Indeed, such differences are a necessary condition for the practice of ecclesiastical toleration because, in their absence, such toleration would have no object. The practice of ecclesiastical toleration requires disagreement. At the same time, however, such disagreements are ‘seeds of hatred.’ For, as long as they subsist, they remain potential reasons of violent conflict and schism. In other words, if ecclesiastical toleration is a virtual union in virtue of the active goal of complete agreement it pursues, it is also virtual schism by the situation of disagreement that it tacitly, or passively, acknowledges the existence of.

I think this double-sided notion reflects Leibniz’s most considered conception of toleration. It implies that ecclesiastical toleration, at the same time as it represents a crucial stage toward union, also represents a stage where sliding back into hatred and intolerance remains a constant and non-eliminable risk. On this point, Leibniz’s Tentamen echoes Molanus’ 1704 Unpartheyisches Urtheil, where the bishop denounced such back-sliding in less abstract terms, as a concrete problem to which the history of Protestantism had borne witness only too often:

[A]s good and Christian, laudable and useful as mutual tolerance [mutua tolerantia] and virtual union [virtualis unio] of protestants [Evangelischen] may appear in theory, yet it has invariably given rise to such bad effects in practice and in its application … that moderate, or even very moderate Lutherans [Evangelicis] who … consider the Calvinists [Reformierten] as brothers in Christ, have with good reason not approved such tolerance since the conditions of the Evangelical Church have always become worse for it, and each time at least a secret persecution and oppression has followed, and more than once public conversion and persecution of our [people].41

In sum, a situation of ecclesiastical toleration is an essentially tense one because it includes, potentially or ‘virtually’ as Leibniz puts it, two opposing tendencies: an active tendency toward union and a passive tendency to slide back into violent schism. These contrary tendencies are embedded within the notion of ecclesiastical toleration itself on account of the admission of disagreement that explains the need for it. Consequently, the ideal horizon for the exercise of ecclesiastical toleration, i.e. the elimination of all hatred and schism by reason of charity, necessarily involves the dissolution of ecclesiastical toleration itself. On the ideal horizon of complete reunion, ecclesiastical toleration simply no longer has any object or application. For, at this endpoint, there is nothing more to tolerate to the extent that the charitable exchange of perspectives that defines the exercise of ecclesiastical toleration no longer has any discernible divergences that it can be applied to. I see myself in my neighbor as he sees himself in me, a situation Leibniz also sometimes identifies with piety understood as perfect justice or ‘universal benevolence.’

One could object that Leibniz’s argument regarding the ‘seeds of hatred’ subsisting in ecclesiastical toleration is bound to specific circumstances and that no general conclusions should be drawn from the Tentamen alone. However, remarks about toleration made in other contexts also suggest that, even in a situation of implemented toleration, the causes of ‘evil’ still remain (Promemoria zur Frage der Reunion der Kirchen, November 1687, A I.v.11, trans. in Leibniz 2005: 248). And this, I would suggest, is probably the most important reason why Leibniz’s notion of toleration is not comparable to the constitutive ideal that modernity has embraced. Not only is toleration, for Leibniz, not foundational as an ideal. It is also ambiguous: by seeking to mitigate from within the pernicious effects of schism and conflictual religious plurality it also, at the same time, acknowledges and allows for the existence of such schism and conflictual plurality. Consequently, toleration contains, as a kind of shadow within it, the very thing it is designed to counter, namely theological hatred. This is why, in a Promemoria zur Frage der Reunion der Kirchen from 1687, while stressing that it is ‘always necessary to begin’ with ‘the way of mutual toleration and civil peace’, Leibniz immediately goes on to stress that this only ‘mitigates evil rather than eliminating its cause, like physicians who begin their healing by the most pressing symptoms’ (Promemoria, A I.v.11, trans. in Leibniz 2005: 248). Practicing ecclesiastical toleration is always, at the same time as it is an exercise in charity, a tacit admission of the fact that the goal of piety is also the end of toleration. Unity simply eliminates the need for it.

4. Toleration and Freedom of Expression

Ever since Spinoza and his defense of the libertas philosophandi in chapter XX of the Tractatus Theologico-Politicus, freedom of expression has come to be seen as an essential component of a tolerant society. Conversely, a society of censorship is generally seen as intolerant. Toleration and censorship are considered, if not necessarily mutually exclusive in practice, then at least as expressing contrary attitudes: more of the one means less of the other, and vice versa. Did Leibniz subscribe to such direct proportionality between toleration and freedom of expression?42

There certainly are passages going in that direction. Hence, writing to Bartholomew des Bosses concerning the persecutions of Jansenists in France, he noted: ‘Even if I do not approve of the main views of an author, I should like to have conceded to the learned … the freedom of philosophizing, which inspires competition and arouses intellects’ and warns that ‘it is extremely harmful that freedom of opinion be restrained from day to day within unnecessary limits’ (to Des Bosses, 21 July 1702, in Leibniz 2007: 93 and 95). He staunchly opposed the censorship of Galileo and clearly defended the right to freely conduct scientific research having no immediate implications for morality or religion: ‘I have no objections to refuting authors whose opinions are dangerous, but I do not know whether it is suitable to establish a sort of inquisition against them, when their false opinions have no influence on morality.’43 Moreover, when it came to authors who did write things that could prove morally detrimental, he favored efficient refutation over repression: ‘I am thus of the opinion that one can and must respond to the objections put forward by libertines, atheists, infidels and heretics’ (to Jaquelot, 6 October 1706, Grua 66–67).’ And yet Leibniz also clearly believed that there were necessary limits to uphold: ‘[W]hen there is question of toleration, one should not condemn hastily, but still … one should not be negligent either when a doctrine is dangerous’;44 ‘one has the right to take precautions against bad doctrines that influence the mores and the practice of piety’ (Nouveaux essais sur l’entendement humain, IV, xvi, § 4, A Hence, writing to Thomas Burnett in 1710, he insisted that ‘one is perfectly right to declare oneself against atheist and libertine books which are more dangerous than the Socinians and prevent their diffusion’ (to Burnett, [1710], GP III.319). He believed that it was the role of the governing political authorities to repress evidently dangerous publications through state control over the publishing business.45

Hence, Leibniz recommended a regime of centralized and systematic censorship which, on the face of it, sits somewhat uneasily with the ‘freedom to think and to say what one thinks’ championed by Spinoza. This is not to say that Spinoza recommended ‘free speech’ as an individual right in the modern, liberalist sense. Spinoza’s philosophical notion of freedom as rational self-determination informs not only his ethics and politics but also his conception of the freedom of philosophizing, inviting use to avoid any such facile assimilation of his position to present-day conceptions.46 For Spinoza, permitting free philosophizing was mostly about creating the best conditions for a public sphere wherein the rationality of the people could develop. He was not granting a general license to say—or even think!47—anything whatsoever. He even cautioned that it would be ‘disastrous to grant it completely’ (G III.240/C II.345), excluding ‘deception, anger, hatred’ and any ‘intention to introduce something into the republic on the authority of [one’s] own decision’, presumably on the grounds that such speech and action does not qualify as free in any positive sense (G III.241/C II.346–47). Nonetheless, a significant contrast between Leibniz and Spinoza’s positions remains, in that the fundamental criterion behind Leibniz’s conception of censorship was not that of freedom in any sense, but rather that of moderation and charity in controversy. Hence, the only positions to be subjected to censorship were immoderate or extremist positions—including atheism, libertinism, enthusiasm, radical fideism—, and such positions as Leibniz saw as incapable or unwilling to ‘go all the way round the thing’, or adopt ‘the viewpoint of the other’ in order to judge equitably. Moreover, such immoderate doctrines should be subjected only to moderate censorship by suppressing writings while abstaining from persecuting the authors; by clamping down only on such dangerous opinions which gave rise to sects or movements; and—here echoing Bayle’s position—by taking into account that beliefs are not voluntary.48

Leibniz’s conception of legitimate, moderate censorship has implications for his stance vis-à-vis another component of modern toleration, namely the admission of atheists. Those authors whose books Leibniz recommended be censored were principally those whom he labelled ‘libertines’ and ‘atheists.’ And yet we should not see in Leibniz someone who thought people should be muted on account of their religious beliefs, or lack thereof. Moreover, he did not reject Bayle’s argument in the Pensées diverses regarding the possibility of a virtuous atheist. In fact, in the Nouveaux essais, he appears to subscribe to it:

I know that excellent and well-intentioned men maintain that these theoretical opinions have less of an influence in practice than one might think, and I also know that there are people of excellent disposition whose opinions would never lead them to do anything unworthy of them. … and one can say that Epicurus and Spinoza, for example, have both led a perfectly exemplary life (Nouveaux essais, VI, x, §4, A

Leibniz did however differ from Bayle in thinking that an atheist could only be virtuous from habit or disposition, but not from a moral conscience grounded in right reason, thus making his virtue merely contingent, grounded in (personal) history and experience and not in rational principle: ‘an atheist can be a good man, morally speaking, by temperament, by habit or by some fortunate prejudice, but he cannot be so by a firm principle of right reason’ (to Mathurin Veyssière de la Croze, 2 December 1702, in Dutens V.484).

The relation between Bayle and Leibniz is further complicated by the fact that they did not entertain the same conception of atheism. For Bayle, Christian faith was inseparable from speculative truths of a revealed, ‘supernatural order’ (Bayle 1820: XV.310). Atheism was, for him, tied to the rejection of those truths. As for the basic practical principles of Christian faith, charity above all, they were ultimately grounded in right reason and common notions of moral conscience and not in religious faith. This is why he denied that those Christians ‘who do not live according to the principles of their religion … are all hidden atheists’ (Bayle 2007: § 139, 299), but affirmed that those who do live according to those principles can in fact very well be atheists. In fact, the ‘spirit of debauchery does not depend on the opinions one does or does not entertain regarding the nature of God, but on a certain corruption which stems from the body and which is strengthened every day by the pleasure one finds in such voluptuousness’ (Bayle 2007: § 144, 309).

For Leibniz, on the contrary, ‘atheism’ was not primarily defined by the denial of revealed, supernatural truths. Certainly, he did occasionally define atheism in terms of dogmatic assertions regarding the existence of God, providence, and the immortality of the soul: ‘An atheist is he who does not acknowledge a wise and powerful governor rewarding the good and punishing the evil after death. Consequently, he who denies the immortality of the soul is an atheist’ (Grua 740–41). However, such a person is reproachable exactly because ‘the doctrine of providence is useless if the immortality of soul is taken away’, for in this case ‘natural theology becomes vain, and is worth nothing against practical atheism’ (to Bierling, [undated], GP VII.511; my italics). For Leibniz, contrary to Bayle, libertinism and atheism were first of all practical categories, referring less to propositions and doctrines than to moral attitudes and patterns of behavior. Libertines and atheists were such people as posed a threat to the social fabric, hostile to public security and the best interests of mankind. Atheists and libertines were not just, in Leibniz’s terminology, people who proposed arguments against the revealed truths of Christian religion. They were people who, fearing no God, would ‘completely give in to their brutal passions and turn their mind to seducing and corrupting others’ (Nouveaux essais, IV, xvi, § 4, A By definition, they were, as Leibniz put it to Gottlieb Spitzel, ‘an evil from which to expect nothing less than universal anarchy and the overturning of society’ (to Gottlieb Spitzel, 10/20 February 1670, A II.ii.55).

Hence, if Leibniz embraced some form of state censorship, it was because he was deeply concerned by the way public opinion could be swayed and manipulated by unscrupulous practical atheists. In a text on public security from 1670, Leibniz thus warned of all the einreissenden Atheismus in Germany corrupting the youth and threatening morality and religion.49 And when writing Arnauld in 1671, he expressed his concern that ‘impiety spreads everywhere’ and the fear that atheist opinions should ‘surreptitiously take over’ people’s minds’ (to Arnauld, November 1671, A II.i.277). Now, one of the primary problems with such atheist libertines—this ‘sect of all sects’, ‘the most dangerous sect of them all’ according to a 1683 letter to Seckendorf (A I.iii.572)—was that they represented a substantial threat to ecclesiastical toleration. Schism had given rise to mutual rejection among confessions. Atheist libertinism represented the logical endpoint of such recriminations to the extent that it represented their degeneration into a general rejection of religion altogether. Hence, in 1691, in De religionis pace, Leibniz described how ‘the greatest evils have risen from the disagreement among religions: hate and distrust, murderous wars, the rise of incredulity, horrible sects in England and Holland, libertine ways, and the whole contempt of religion’ (De religionis pace, circa 1691, A IV.iv.544). Atheism and libertinism were, in sum, the logical outcome of religious controversies when they cultivated the ‘seeds of hatred’ described by Leibniz in the Tentamen, i.e. when the participants in controversy seized upon the most pernicious aspects of religious plurality. Their rise to prominence was, in fact, the effect of generalized religious intolerance or the rejection of all religion. No wonder, then, that Leibniz stressed that ‘we should now put considerable more effort into combating atheism and deism than heresy’ (to Ernst von-Hessen Rheinfels, 4 (14) March 1685, Grua 196). In fact, combating atheism was, for him, no different than combating religious intolerance. Indeed, by Leibniz’s lights, there was something almost contradictory about calling for the toleration of atheists in the way Bayle did, to the extent that, on Leibniz’s definition of atheism at least, this amounted to promoting the toleration of intolerance.

In sum, then, Leibniz differed from the modern conception of toleration by maintaining, contrary to Locke, unity and the cancellation of difference as a regulative ideal that had to be on the horizon of toleration as a necessary guiding principle. He differed from Bayle in denying that atheists could be safely tolerated. In fact, suppressing and censoring atheism and libertinism was necessary to defend toleration as he understood it, namely as something conducive to future confessional conciliation. Moreover, against Bayle, he denied that the principles of right moral reason could be established independently of religion. Finally, Leibniz was less concerned with the suppression of individual liberties than with rise of forms of extremism, less concerned with defending individuals’ autonomy than with ascertaining their moderation in their exchanges with others. Consequently, he was at odds with Spinoza when denying that the relation between toleration and freedom of expression was directly proportional.

5. Conclusion

I have argued that Leibniz’s explicit conception of toleration was substantially different from the modern notion of toleration. In order to understand why, it is important to stress the constitutive features of the modern conception of toleration which cannot be reduced to simply an opposition to coercion of beliefs. The modern conception, I think, involves a deeper inclusive embrace of diversity, religious and otherwise, as a value in and by itself, intrinsically linked to an equally fundamental imperative of freedom of expression allowing such diversity to flourish publicly. I have argued, following numerous other commentators, how the philosophical genesis of this modern conception of toleration can be traced back to a constellation of writers including Locke, Bayle and Spinoza. I have also argued that Leibniz is not a star in that constellation. As a post-Reformation thinker of conciliation, be belonged to another, older tradition.

By pointing out these decidedly pre-modern features of Leibniz’s conception of toleration, I have in no way intended to pass a negative judgment on him or reduce his position to some backwards remnant of an outdated theological-political paradigm. Quite to the contrary: despite its shortcomings, I think there is much that is attractive in Leibniz’s conception, as I also think there are fundamental difficulties in the modern conception of toleration that we, today more than ever, have come to experience firsthand not only as troubling conceptual inconsistencies but also as political and societal problems that shape our very lives. There are of course aspects of Leibniz’s position where he, for contemporary sensibilities, does not go nearly far enough—after all, despite gestures toward the Chinese for example, his conciliatory efforts focus on the Christian Churches and are decidedly Eurocentric or even, in some instances, Germano-centric.50 His alleged multiculturalism is shot through with orientalism to put it in contemporary terms.51 Indeed, large swaths of his discussions of China, for example, can be seen as a foil for discussing issues and doctrines that are, in the end of the day, European.52 The Muslim world is, by and large, depicted as a political enemy against whom to wage war.53

Nonetheless, there are aspects of Leibniz’s conceptions from which we can acquire a better grasp of the difficulties that modern toleration faces, such as his insight regarding the embryonic hatred necessarily contained within the very practice of toleration, or the question mark he puts after the contention that diversity can be coherently embraced as a constitutive value. Do we not require at least some regulative ideal of unity? And if we do, what shape could that ideal take today, when the notion of a Christian Commonwealth or a minimal apostolic creed are no longer appropriate options? Finally, Leibniz’s take on censorship and licentious writing may contribute meaningfully, by way of provocation, to a necessary discussion of what relation, exactly, we should see between toleration and liberty of expression, if not an inherent one. Leibniz was deeply concerned, for example, that a completely unregulated press might very well go rogue and favor the rise of such devious libertine atheists—persons constrained by no moral principle—who, if victorious, would prove catastrophic for peace, public security and, indeed, toleration. It is a point that, today, we would be hard-pressed to deny.


1Unless otherwise indicated, translations are my own. 

2Following Rainer Forst, I adopt a relatively relaxed attitude to the terms ‘tolerance’ and ‘toleration’ and do not distinguish between them too systematically (Forst 2013: 1, note 1). I will, however, mostly use the term ‘toleration.’ None of the languages in which Leibniz wrote—Latin, German, and French—make the distinction. 

3For a similar point, see Forst 2013: 262. 

4To the Count of Boinebourg, 2/12 July 1697, A I.xiv.317: ‘Quand j’estois à Helmstät il y a quelque mois j’exhortay fort Monsieur le Docteur Calixtus de pousser son dessein de faire réimprimer entre autres traités de feu son pere, celuy qui regarde la toleration Ecclesiastique des Reformés, où cet excellent homme avoit fort bien monstré, que la division des sentimens qu’il y a, ne devroit point empecher jungi dextras fraternitatis.’ The edition in question appeared with an introduction by his son F. U. Calixtus in 1697. Leibniz’s formulation echoes the position of Molanus, his ally in the negotiations for the reunion of the protestant churches and a fervent disciple of Calixtus, developed in the 1704 Unpartheyisches Urtheil von dem Nutzen, welschen die Evangelischen-Lutherischen aus der Vereinigingen mit dem Reformierten zu erwarten haben (Leibniz 1734–1742: I.164–67, esp. 165: ‘[We] could and should not only tolerate others, but consider each other as brothers in Christ.’ For the constant association of toleration with ‘fraternity’, see also Unvorgreiffliches Bedencken über eine Schrift genandt Kurze Vorstellung, around 11 February 1699, A IV.vii.569, 572, 576; To Johann Fabricius, February 1702, A I.xx.802; Leibniz [in the name of Molanus] to Benjamin Ursinus von Bär, April 1705, A I.xxiv.519. On the conception of toleration of Leibniz and Calixtus, see also Notae marginales in F. U. Calixti dedicationem etc., September–October 1697, A IV.vii.325–26; Unvorgreiffliches Bedencken, A IV.vii.576, 638; To Johann Fabricius, February 1702, A I.xx.802. 

5A significant exception is the work by Claire Rösler-Le Van in her French edition of the documents and correspondences related to Leibniz’s project of a reunion of the protestant churches. Rösler-Le Van asserts no specific position regarding Leibniz’s place in the more general history of toleration, but reinserts his conception decisively into what I also see as its most important context: the irenical negotiations. See Jablonski and Leibniz 2013. See also my review of that volume in Lærke 2016. 

6Antognazza 2002; Antognazza 2013. Nicolas Jolley essentially agrees with Antognazza about her assessment of Leibniz’s commitment to religious toleration, although he also stresses essential differences between Leibniz’s ‘ecumenism’ and Locke’s ‘toleration’ (Jolley 2007). 

7I first pointed this out in a paper published over a decade ago (Lærke 2008[b]). Both Claire Rösler-Le Van and Maria Rosa Antognazza subsequently responded with a number of valid criticisms making me realize that a considerably more sophisticated argument was required. The present article is the result of this reevaluation of my own position. 

8One reviewer wondered if it would be appropriate to consider any possible evolution in Leibniz’s views on toleration throughout his career. I think the answer should be negative. Leibniz’s explicit engagement with the notion of ‘toleration’ largely falls within the decade around the turn of the century and is constant although the detail in which he addresses the notion varies. More generally, one could note that Leibniz’s speculative theology, both natural and revealed, evolved with his metaphysics, but that these developments had few implications, if any at all, for the theological issue of toleration which he saw as an entirely practical one. For the best available, comprehensive study of speculative issues of theology in Leibniz and their development, see Antognazza 2007. For a shorter survey of Leibniz’s religious views, see Lærke 2019. 

9See Antognazza 2013. For another recent paper focusing on this exchange, see Priarolo 2016. 

10To Comtesse de Bellamont, July 1703, in Grua 216. 

11See Castellio 1554. For a commentary, see Zagorin 2003: 93–144. 

14See Zagorin 2003: 245: ‘Aside from Spinoza, Locke and Bayle were the most important thinkers to deal with the problem of toleration in the later seventeenth century.’ See also Israel 2000; Israel 2005: chap. 5; Milton 2012; Forst 2013: 169–70; Forst 2017. Mariangela Priarolo adopts an approach to Leibniz similar to my own, dedicating a section of her analysis to the background for Leibniz’s notion of toleration in Bayle in particular (Priarolo 2016: 747–51). 

15For a good and, in this context, central example, see the remarks on Pellisson in Priarolo 2016: 751–53. 

16For a highly detailed study of the genesis of modern toleration in the intellectual cross-field between Locke and Bayle (but not Spinoza), see Marshall 2006. 

17For a good example, see Gilbert Burnet, a prominent English latitudinarian, writing to Leibniz on church reunion: ‘The only way in my poor opinion to establish a good correspondence among you is to follow the method that we have followed so happily in England … we do all not only hold one communion but live in great friendship together notwithstanding that diversity of opinion’ (Burnet to Leibniz, 27 February 1699, A I.xvi, 595, my italics; also quoted in Antognazza 2009: 403). 

18I here report the most generous reading of Locke because I am interested only in those commentaries which attribute a genuine contribution to modern toleration to him. A good, recent example can be found in Bejan 2017: 112–43. But it should be noted that another, important strand of contemporary scholarship tends to see Locke as considerably less forward-looking and mostly perpetuating a somewhat tepid notion of toleration as mere indulgence. The literature of the debate is too extensive to account for in a footnote. 

19Note that the passage in square brackets is not authentically Lockean, but was added by his English translator, William Popple. 

20Matthew 5:43–44: ‘You have heard that it was said, ‘You must love your neighbor’and hate your enemy.’ But I say to you, love your enemies, and pray for those who persecute you.’ 

21Locke to Limborch, September 1689, in Locke 1979–1989: Ill.689. 

22Bayle 2007. For an English translation, see Bayle 2000. 

23For a recent French edition, see Bayle 2014. For an English translation, see Bayle 2005. 

24See Jurieu 1687, which, according to the title, aims at ‘destroying the doctrine of indifference among religions and universal toleration, against a book entitled ‘Philosophical commentary’.’ The addition sometimes found in the title of Bayle’s book ‘… or Treatise of Universal Toleration’ appears in the 1713 edition, but not in the original or in the edition included in vol. II of the 1737 Oeuvres diverses. Indeed, in that work, Bayle speaks nowhere of ‘universal toleration.’ Incidentally, Locke too was accused of promoting ‘universal toleration’ by Bishop Stillingfleet according to whom ‘an universal Toleration is that Trojan Horse which brings in our enemies without being seen’ (Stillingfleet 1680: 58). 

25For an English translation, see Voltaire 2000. 

26See note 18 above. For the most sophisticated work on the topic, see Rosenthal 2001, 2003, 2012. 

27See e.g. the letter to Daniel Larroque, End November (?) 1692, A I.vii.547–48, where Leibniz associates toleration with the ‘party of moderation.’ 

28To James Cresset, Hanover, 6 (16) November 1697, A I.xiv.690–91. On this text, see also Antognazza 2009: 402–3. Leibniz is quoting Horace, Epistles, I, Letter 1. 

29See for example the letter to Johann Jacob Julius Juno, 7 (17) October 1697, A I.xiv.593–95. 

30Leibniz [writing as Gerhard Wolter Molanus] to Daniel Ernst Jablonski, 10 May 1701, A I.xix.670. For that distinction, see also Leibniz, De Pellissonii Reflexions sur les differends de la religion, 4 May 1692, A IV.iv.552–53; to Ludolf, 5 (15) November 1697, A I.xiv.682; to Cresset, 6 (16) November 1697, A I.iv.691; to Ludolf, 30 May (9 June) 1698, A I.xv.629; to Jablonski, 8 (18) January 1699, A I.xvi.473; Leibniz [in the name of Duke Anton Ulrich] for King Friedrich I. and Benjamin Ursinus von Bär, 15 May 1705, A I.xxiv.607. 

31See Reunion der Kirchen, 1683, A IV.iii.286. 

32See Unvorgreiffliches Bedencken, A IV.vii.448. 

33See for example Judicium de annotatis placidis ad Tentamen expositionis irenicae, after 11 February 1699, A IV.viii.340; Nach Durch Adams Fall und der allen Menschen angebohren Erbsunde, 1697/98, A IV.vii.337; to Johann Jacob Julius Juno, 7 (17) October 1697, A I.xiv.595. 

34Nouveaux essais, I, chap. 3, § 4, A See also Méditation sur la notion commune de la justice, 1702, in Leibniz 1893: 57, translated in Leibniz 1995: 56: ‘This fitness or what is due is determined by the rule of equity or of equality: Quod tibi non vis fieri aut quod tibi vis fieri, neque aliis facito aut negato. It is the rule of reason and of our Master. Put yourself in the place of another and you will have the true point of view for judging what is just or not.’ Cf. Matt 7:12, Luke 6:31, and Tobias 4:15. 

35See Gil 1984; Dascal 1993; Lærke 2010. For the ‘art of controversies’, see Leibniz 2005. 

37For another text where Leibniz speaks of complete reunion, see Unvorgreiffliches Bedencken, A IV.vii.434. 

39See Leibniz’s notes on the latitudinarian position of Gilbert Burnet, in Sur G. Burnet, An Exposition of the Thirty Nine Articles of the Church of England, December 1700-April 1701 (?), A IV.viii.373–74: ‘[H]is aim, however has been to facilitate toleration among the two parties dividing protestants …. One could add … that only too often the controversies are only apparent, and cease to exist when only one explains the terms correctly.’ For the different approaches to protestant and complete church reunion, compare, respectively, Leibniz’s letter to Jablonski in Berlin in 1699 (which stresses full union) and to Bossuet in France two years later (which calls for toleration, while leaving ‘private’ differences): To Jablonski, 19 (29) October 1699, A I.xvii.587, and to Bossuet, August–September 1701, A I.xx.428. 

40For the association of ‘virtual union’ and ‘mutual toleration,’ see also Unvorgreiffliches Bedencken, A IV.vii.434, 436, 568–69, 576; and Molanus to Leibniz, 10 April 1705, A I.xxiv.535, which describes a ‘brotherhood’ involving ‘only toleration and not actual union.’ 

41Included in Leibniz 1734–1742: I.164–67, here 164–65. On this text, including a French translation, see Jablonski and Leibniz: 857–94. Rösler-Le Van somewhat downplays the parallel to Leibniz’s Testamen, arguing that ‘Leibniz did not really share Molanus’s concerns, even though he understood them’ (Jablonski and Leibniz 2013: 891). 

42I have addressed Leibniz’s approach to freedom of expression in two earlier publications dedicated to Leibniz’s approach to censorship: Lærke 2007, 2009. For this article, I draw on the primary material gathered for those two publications, but in order to address the specific question of how Leibniz saw the relation between toleration and freedom of expression. The question is very briefly mentioned in Lærke 2007: 14, and in Lærke 2009: 156–57. 

43To Burnett, [23 January 1698], GP III.221. See also letter to Magliabecchi, October 1699, Dutens V.128: ‘When I was in Rome, I encouraged certain distinguished men with authority, that they might favor philosophical freedom [libertati philosophica] in [relation to] questions of no great danger.’ See also Robinet 1988: 58–59, 96–118; Antognazza 2009: 301–2. 

44Reflexions sur un écrit irénique de Fetizon, After 20 August 1700, A IV.viii.368–69. 

47See G III.242/C II.348: ‘If someone thinks that the supreme power isn’t its own master, or that no one ought to keep his promises, or that each person ought to live according to his own decision, or something else of this kind, directly contrary to the agreement mentioned above, he is seditious. This isn’t so much because of the judgment and opinion as because of the action such judgments involve. For by the very fact that he thinks such a thing, he cancels the assurance he’s given, either tacitly or explicitly, to the supreme power’ (my italics). 

48See Lærke 2009. Generally, on Leibniz’s intellectual ethics of moderation, see Lærke 2015: 98–104. 

49See Securitas publica, August 1670, A IV, i, 133–34. See also Leibniz to Johann Friedrich, 21 May 1671, A II.i.175. 

50This is partly why Rösler-Le Van resists the characterization of Leibniz’s philosophical irenicism as an ‘ecumenism’, a notion that etymologically suggests universality (see Jablonski and Leibniz 2013: 790). 

51Leibniz may have kept an open mind toward other cultures and religions. But he consistently depicted and evaluated those cultures through a euro-centric lens. For a paper on the topic, see Cook 2008. On Leibniz’s ‘multiculturalism’, see Antognazza 2009: 359–65. 

52See for example Leibniz’s descriptions in the Novissima Sinica of the Chinese Emperor who ends up looking conspicuously like Hobbes’ Leviathan (see Leibniz 1994: 48); or consider his portraits of the atheist Chinese literati in his 1708 remarks on Chinese rites and religion and of the duplicitous mandarins at the Chinese imperial court in the Discours sur la théologie naturelle des Chinois. They are entirely modeled on the standard image of a European esprit fort, Epicurean, atheist, materialist, political, sectarian, secretive, etc. (Leibniz 1994: 71–72, 96–97, 108–109, 118–19, 130–31). 

53The project of the Consilium Aegyptiacum (1671), proposing that the French king invade Egypt, as also his later promotion of the Empire’s war on the Turks to the French, were attempts at deflecting internal European conflicts by directing the European sovereigns toward a shared common enemy, i.e. the Muslim world. 

Competing Interests

The author has no competing interests to declare.



      1. A: Sämtliche Schriften und Briefe, edited by the Akademie der Wissenschaften. Berlin: Akademie-Verlag, 1923. 

      2. Dutens: Opera omnia, edited by Ludovico Dutens, 6 vols, Genève: Fratres de Tournes, 1768. 

      3. GP: Die philosophischen Schriften von G. W. Leibniz, edited by Carl I. Gerhardt, 7 vols. Berlin: Weidmannsche Buchhandlung, 1875–1890. 

      4. Grua: Textes inédits, edited by Gaston Grua, 2 vols. Paris: Presses universitaires de France, 1948. 

      1. LCT: A Letter Concerning Toleration, edited by Mario Montuori. The Hague: Martinus Nijhoff, 1963. 

      1. C: The Collected Works of Spinoza, edited and translated by Edwin Curley, 2 vols. Princeton: Princeton University Press, 1985–2015. 

      2. G: Opera, edited by Carl Gebhardt, 4 vols. Heidelberg: Carl Winter, 1925. 

    Other Texts Cited

    1. Antognazza, Maria Rosa. Leibniz. An Intellectual Biography, Cambridge: Cambridge University Press 2009. DOI: 

    2. Antognazza, Maria Rosa. “Leibniz and Religious Toleration: The Correspondence with Paul Pellisson-Fontanier.” American Catholic Philosophical Quarterly 76, no. 4 (2002): 601–622. DOI: 

    3. Antognazza, Maria Rosa. Leibniz on the Trinity and the Incarnation. Reason and Revelation in the Seventeenth Century. New Haven: Yale University Press, 2007. DOI: 

    4. Antognazza, Maria Rosa. “Leibniz’s Doctrine of Toleration: Philosophical, Theological, and Pragmatic Reason.” In Natural Law and Toleration in the Early Enlightenment, edited by Jon Parkin and Timothy Stanton, 139–164. Oxford: Oxford University Press/The British Academy, 2013. DOI: 

    5. Bayle, Pierre. A Philosophical Commentary on These Words of the Gospel, Luke 14.23, “Compel Them to Come In, That My House May Be Full”, edited by John Kilkullen and Chandran Kukathas. Indianapolis: Liberty Fund, 2005. 

    6. Bayle, Pierre. De la tolerance. Commentaire philosophique, edited by Jean-Michel Gros. Paris: Champion, 2014. 

    7. Bayle, Pierre. Dictionnaire historique et critique, 16 vols. Paris: Desoer, 1820. 

    8. Bayle, Pierre. Pensées diverses sur la comète, edited by Joyce and Hubert Bost. Paris: GF Flammarion, 2007. 

    9. Bayle, Pierre. Various Thoughts on the Occasion of a Comet, translated by Robert C. Bartlett. Albany: State University of New York Press, 2000. 

    10. Bejan, Teresa. Mere Civility. Disagreement and the Limits of Toleration. Cambridge, Mass.: Harvard University Press, 2017. DOI: 

    11. Castellio, Sebastian. De haereticis an sint persequendi, & omnino quomodo sit cum eis agendum. Magdeburgi: Per Georgium Rausch, 1554. 

    12. Cook, Daniel. “Leibniz and ‘Orientalism.’” Studia Leibnitiana 40, no. 2 (2008): 168–190. 

    13. Cook, Thomas. “‘Libertas Philosophandi’ and Freedom of Mind in Spinoza’s ‘Tractatus Theologico-Politicus.’” Tijdschrift voor Filosofie 74, no. 2 (2012): 215–240. DOI: 

    14. Dascal, Marcelo. “Introductory Essay,” in G. W. Leibniz, The Art of Controversies, edited and translated by M. Dascal, Q. Racienero and A. Cardoso, xix–lxxii. Dordrecht: Springer 2005. 

    15. Dascal, Marcelo. “One Adam and many cultures: The role of political pluralism in the best of possible worlds.” In Leibniz and Adam, edited by Marcelo Dascal and Elhanan Yakira, 387–409. Tel Aviv: University Publishing Projects, 1993. 

    16. Forst, Rainer. Toleration in Conflict. Past and Present. Cambridge: Cambridge University Press, 2013. 

    17. Forst, Rainer. “Toleration.” In Stanford Encyclopedia of Philosophy, edited by Edward Zalta. Last revised 12 July 2017. 

    18. Gil, Fernando. “Leibniz, la place d’autrui, le principe du pire et la politique de la monadologie.” Passé Present 3 (1984): 147–164. 

    19. Holz, Hans Heinz. “Lessing und Leibniz. Pluralismus, Perspektivität und Wahrheit.” In Lessing und die Toleranz, edited by P. Freimark, F. Kopitzsch und H. Slessarew, 11–23. Detroit: Wayne State University Press, 1986. 

    20. Israel, Jonathan I. Enlightenment Contested. Oxford: Oxford University Press, 2005. 

    21. Israel, Jonathan I. “Spinoza, Locke and the Enlightenment Battle for Toleration.” In Toleration in Enlightenment Europe, edited by Ole Peter Grell and Roy Porter, 102–113. Cambridge: Cambridge University Press 2000. DOI: 

    22. Jablonski, Daniel Ernst, and Gottfried Wilhelm Leibniz. Negotium irenicum. L’union des Églises protéstantes selon G. W. Leibniz and D. E. Jablonski, edited and translated by Claire Rösler-Le Van. Paris: Classiques Garnier, 2013. 

    23. Jablonski, Daniel Ernst, and Gottfried Wilhelm Leibniz. Neue Beiträge zum Briefwechsel zwischen D. E. Jablonski und G. W. Leibniz, edited by J. Kvačala. Jurjew C. Mattiesen, 1899. 

    24. Jolley, Nicolas. “Leibniz, Locke, and the Epistemology of Toleration.” In Leibniz and the English-speaking World, edited by Stuart Brown and Pauline Phemister, 133–143. Dordrecht: Springer 2007. DOI: 

    25. Jurieu, Pierre. Des droits des deux souverains en matière de religion, la conscience et le prince, pour détruire le dogme de l’indifférence des réligions et de la tolérance universelle, contre un livre intitulé ‘Commentaire philosophique.’ Rotterdam: Henri de Graef, 1687. 

    26. Lærke, Mogens. “D. E. Jablonski and G. W. Wilhelm. Negotium irenicum. Edited and translated by Claire Rösler-Le Van. Paris: Classiques Garnier 2013.” The Leibniz Review 26 (2016): 207–213. DOI: 

    27. Lærke, Mogens. “G. W. Leibniz: Moderation and Censorship.” In The Use of Censorship in the Enlightenment, edited by Mogens Lærke, 155–178. Leiden: Brill, 2009. DOI: 

    28. Lærke, Mogens. “Leibniz et la tolerance.” Bulletin de l’Institut d’Histoire de la Réformation 28 (2008[b]): 29–47. 

    29. Lærke, Mogens. “Leibniz, la censure et la libre pensée.” Archives de philosophie 70, no. 1 (2007): 273–287. DOI: 

    30. Lærke, Mogens. Leibniz lecteur de Spinoza. La genèse d’une opposition complexe. Paris: Champion, 2008[a]. 

    31. Lærke, Mogens. Les Lumières de Leibniz. Controverses avec Huet, Bayle, Regis et More. Paris: Classiques Garnier, 2015. 

    32. Lærke, Mogens. “On Religion.” In Leibniz e la cultura enciclopedica, edited by Massimo Mori, 249–283. Bologna: Il Mulino, 2019. 

    33. Lærke, Mogens. “The Golden Rule: Charitas/Prudentia. Aspects of G. W. Leibniz’s Method for Religious Controversy.” In The Practice of Reason: Leibniz and his Controversies, edited by Marcelo Dascal, 297–319. Amsterdam/Philadelphia: Andrew Benjamin Publishing, 2010. DOI: 

    34. Laursen, John Christian. “Introduction: Contexts and Paths to Toleration in the Seventeenth Century.” In Beyond the Persecuting Society. Religious Toleration before the Enlightenment, edited by John Christian Laursen and Cary J. Nederman, 169–177. Philadelphia: University of Pennsylvania Press, 1998. 

    35. Leibniz, Gottfried Wilhelm. Leibnitii Epistolae ad diversos, edited by Christian Kortholt, 4 vols. Leipzig: Breifkopf, 1734–1742. 

    36. Leibniz, Gottfried Wilhelm. Mittheillungen aus Leibnizens ungdruchten Schriften, edited by Georg Mollat. Leipzig: H. Haessel, 1893. 

    37. Leibniz, Gottfried Wilhelm. Political Writings, edited by Patrick Riley, 2nd edition. Cambridge: Cambridge University Press, 1995. 

    38. Leibniz, Gottfried Wilhelm. The Art of Controversies, edited and translated by M. Dascal, Q. Racienero and A. Cardoso. Dordrecht: Springer 2005. 

    39. Leibniz, Gottfried Wilhelm. The Leibniz-Des Bosses Correspondence, edited and translated by Brandon Look and Donald Rutherford. New Haven: Yale University Press, 2007. 

    40. Leibniz, Gottfried Wilhelm. Writings on China, edited and translated by Daniel J. Cook and Henry Rosemont. Chicago and LaSalle: Open Court, 1994. 

    41. Locke, John. The Correspondence of John Locke, edited by E. S. De Beer. Oxford: Clarendon Press, 1978–1989. 

    42. Marshall, John. John Locke, Toleration and Early Enlightenment Culture. Cambridge: Cambridge University Press, 2006. 

    43. Mill, John Stuart. On Liberty. London: John W. Parker & Son, 1859. 

    44. Milton, Philip. “Religious Toleration,” In The Oxford Handbook of Philosophy in Early Modern Europe, edited by Desmond Clarke and Catherine Wilson, 571–590. Oxford: Oxford University Press, 2012. DOI: 

    45. Pellisson–Fontanier, Paul. De la tolérance des réligions. Lettres de M. de Leibniz et réponses de M. Pellisson ou quatrième partie des réflexions sur les différends de la religion. Cologne: André Pierrot, 1692. 

    46. Perkins, Franklin. “Virtue, Reason and Cultural Exchange: Leibniz’s Praise of Chinese Morality.” Journal of the History of Ideas 63, no. 3 (2002): 447–464. DOI: 

    47. Priarolo, Mariangela. “The Consequences of Error: Leibniz and Toleration.” Rivista di Storia della Filosofia 81, no. 4 (2016): 745–764. DOI: 

    48. Robinet, André. G.W. Leibniz. Iter Italicum. Firenze: Leo S. Olschki Editore, 1988. 

    49. Rosenthal, Michael A. “Spinoza’s Republican Argument for Toleration.” Journal of Political Philosophy 11, no. 3 (2003): 320–337. DOI: 

    50. Rosenthal, Michael A. “Toleration as a Virtue in Spinoza’s Ethics.” Journal of the History of Philosophy 39, no. 4 (2001): 535–557. DOI: 

    51. Rosenthal, Michael A. “Why Spinoza Is Intolerant of Atheists: God and the Limits of Early Modern Liberalism.” The Review of Metaphysics 65 (2012): 813–839. 

    52. Schultze, Harald. Lessing’s Toleranzbegriff. Eine theologische Studie. Göttingen: Vadenhoeck & Ruprecht, 1969. 

    53. Stein-Karnbach, Annegret. “G. W. Leibniz und der Buchhandel.” Archiv für Geschichte des Buchwesens 23 (1982): 1189–1418. DOI: 

    54. Stillingfleet, Edward. Mischief of Separation. London: Henry Mortlock, 1680. 

    55. Voltaire, Treatise on Toleration and Other Writings, edited by Simon Harvey, translated by Brian Masters, Cambridge: Cambridge University Press, 2000. 

    56. Walther, Manfred. “Politische und Ethische Freiheit oder Spinozas Dialektik der Freiheit.” In Ethik, Recht und Politik bei Spinoza, edited by Marcel Senn and Manfred Walther, 89–103. Zürich: Schulthess, 2001. 

    57. Zagorin, Perez. How the Idea of Religious Toleration Came to the West. Princeton: Princeton University Press, 2003. DOI: 

comments powered by Disqus