Moses Mendelssohn (1729-1786)

Key dates

The scribe's son and the "English disease"

Moses Mendelssohn was born on 6 September 1729 in Dessau, a small town in the Principality of Anhalt-Dessau, into a modest Jewish family. His father, Mendel, earned his living as a Torah scribe — a trade of painstaking precision which, according to 19th-century biographers, is said to have developed in the child a keen sense of form and exactness^[20]. During his childhood, Moses contracted what the old sources call the "English disease" (a form of rickets) and developed a severe spinal deformity that left him hunchbacked throughout his adult life^[21]. This physical infirmity, in a society quick to judge a man by his appearance, never prevented him from imposing himself through the sheer force of his intelligence — to the point that his contemporaries described him, despite his unprepossessing physique, as a conversationalist of rare elegance and vivacity.

Rabbi David Fränkel and the discovery of Maimonides

His early education was provided by his father and by the local rabbi, David Fränkel, who taught him the Torah and the Talmud and introduced him to the philosophy of Maimonides^[22]. When Fränkel was appointed chief rabbi of Berlin, the young Moses, then fourteen years old, followed him to the Prussian capital a few months later, in 1743^[23]. Berlin biographical tradition has long preserved a striking anecdote of this arrival: the register of the guard post at the Rosenthal Gate, then reserved for the entry of livestock and Jews, is said to have recorded that day the passage of "six oxen, seven pigs, one Jew"^[24]. Contemporary scholarship, however, counsels caution regarding certain details of this account: it is unlikely that the adolescent walked the entire distance from Dessau to Berlin, a stagecoach journey being far more probable at the time, and nothing establishes with certainty that the Rosenthal Gate was then the city's only entrance open to Jews^[25]. In Berlin, lacking the means to fund regular studies, Mendelssohn educated himself: the mathematician Israel Zamosz taught him mathematics, Abraham Kisch Latin, and Aaron Solomon Gumperz French, English and the rudiments of modern philosophy^[26]. This self-taught formation, pursued under difficult material conditions, forged a mind of uncommon rigour, able to read the metaphysics of Leibniz and Wolff as well as the Greek and Latin classics^[27].

From tutor to partner

In 1750, the wealthy silk merchant Isaac Bernhard hired Mendelssohn as tutor to his children; the young man soon became the bookkeeper, then the partner, of the manufactory^[28]. This commercial activity, which he would continue all his life, secured him relative material independence without ever becoming his true vocation^[29]: his evenings and nights were devoted to philosophy, translation and scholarly correspondence. It was in this setting that, in 1754, the friendship that would change his life was formed: with the playwright and critic Gotthold Ephraim Lessing, three years his senior, who introduced him into Berlin's intellectual circles and encouraged him to publish^[30]. His first writings, published anonymously from 1755 — the Philosophische Gespräche ("Philosophical Dialogues") and a satire co-written with Lessing, Pope, ein Metaphysiker! ("Pope, a Metaphysician!") — already drew the attention of the Berlin Republic of Letters to this unknown young clerk^[31].

The Royal Academy of Prussia prize (1763): ahead of Kant

In 1763, the Royal Academy of Sciences of Prussia set as its prize competition the question of whether metaphysical truths can attain the same degree of evidence as mathematical truths^[32]. Mendelssohn won first prize with his Abhandlung über die Evidenz in den metaphysischen Wissenschaften ("Dissertation on Evidence in the Metaphysical Sciences") — ahead of a competitor who would soon become the greatest philosopher of his century: Immanuel Kant, ranked second^[33]. This success, won by a Jew with no university title against the German philosophical elite, made Mendelssohn an intellectual celebrity overnight^[34]. In October of the same year, it earned him the status of "protected Jew" (Schutzjude), seemingly thanks to the intercession of the Marquis d'Argens with King Frederick II^[35] — a precarious status that would not, however, extend to his wife or children^[36].

Lessing, Nicolai and the Republic of Letters

With Lessing and the publisher Friedrich Nicolai, Mendelssohn co-edited several critical reviews, including the famous Letters Concerning the Most Recent Literature (Briefe, die neueste Literatur betreffend). His critical essays on Homer and Aesop, Pope and Burke, Maupertuis and Rousseau rank among the finest pages of German literary criticism of the century^[37]. This activity as a man of letters, carried on alongside his most technical philosophical work, illustrates a constant trait of the man: the determination to make learned thought a public and cultivated conversation, accessible to the enlightened general public rather than reserved for academics.

Marriage to Fromet Gugenheim

In June 1762, Mendelssohn married Fromet Gugenheim (born 6 October 1737, died 16 March 1812), who would outlive him by twenty-six years^[38]. The couple had ten children, six of whom reached adulthood — a large family whose religious destiny, as will be seen, would prove deeply divided between fidelity to Judaism and conversions to Christianity.

From Abbt to Plato: the genesis of the work

In 1767, Mendelssohn published Phädon, oder über die Unsterblichkeit der Seele ("Phaedon, or On the Immortality of the Soul"), written after the death of his friend Thomas Abbt, who had introduced him to Plato's dialogue^[39]. The work begins as a faithful translation of Plato's Phaedo, then gradually breaks free from it: Mendelssohn develops personal arguments, which he judges more convincing than those of Plato's Socrates, in favour of the immortality of the soul, against the materialism then fashionable in certain Enlightenment circles^[40].

A European triumph

The success was immediate and considerable: the book became one of the most widely read German works of its time, translated into several European languages^[41], and earned its author the nicknames of "Socrates of Berlin" and "German Plato"^[42]. This literary triumph lastingly established Mendelssohn as the most respected Jewish philosopher in Europe — well before Jerusalem would make him, fifteen years later, the great theorist of religious tolerance.

The challenge of a Zurich pastor

Mendelssohn had already met the young Zurich theologian Johann Caspar Lavater in April 1763, during the latter's stay in Berlin^[43]; Lavater had apparently come away with the assurance that the Jewish philosopher respected the morality of Christ, provided the latter had upheld Mosaic orthodoxy^[44]. Six years later, on 25 August 1769, Lavater published a translation of sections of the Recherches philosophiques sur les preuves du christianisme (Philosophical Inquiries on the Evidences of Christianity) by the Genevan apologist Charles Bonnet^[45], accompanying it with a public dedication addressed to Mendelssohn: he called on him either to refute Bonnet's arguments publicly or — if he could not — to do, "as an honest man", what Socrates would have done had he read that work and found it irrefutable, that is, to convert^[46].

Mendelssohn's response: fidelity and tolerance

Deeply troubled — he had always taken care to avoid public religious controversies, including in private — Mendelssohn replied with an open letter published in December 1769.

"I did not begin examining my religion yesterday (...) I have devoted the best part of my life to this inquiry." — Moses Mendelssohn, Schreiben an den Herrn Diaconus Lavater zu Zürich, December 1769^[47]

In it he recalled that Judaism, unlike Christianity, knows no missionary calling and demands no one's conversion:

"According to the principles of my religion, I must not seek to convert anyone who was not born under our law." — Moses Mendelssohn, Schreiben an den Herrn Diaconus Lavater zu Zürich, December 1769^[48]

He justified his reluctance to engage in polemics by his condition as a member of an oppressed people, obliged to preserve the goodwill of the dominant nations^[49], while firmly affirming that he would only ever abjure out of intimate conviction:

"If I had changed faith in my heart, it would be the basest of meannesses not to be willing to confess the truth." — Moses Mendelssohn, quoted by the Jewish Encyclopedia, art. "Mendelssohn"^[50]

On substance, his reply formulated a principle of tolerance that would become the heart of his religious philosophy: one may admire the virtue of a sage outside one's own faith without having to draw from it the absurd obligation to convert to his religion.

"Supposing there lived among my contemporaries a Confucius or a Solon, I could, according to the principles of my faith, love and admire that great man without falling into the ridiculous idea that I would have to convert a Solon or a Confucius." — Moses Mendelssohn, Schreiben an den Herrn Diaconus Lavater zu Zürich, December 1769^[51]

The aftermath of a trial

The controversy, widely commented on throughout cultivated Germany, cost Mendelssohn "much time, energy and strength"^[52] and lastingly affected his already fragile health: in March 1771, he suffered a severe nervous crisis that forced him to interrupt his philosophical work for several months^[53]. Lavater himself, in his later writings, would praise "a brilliant and sociable soul", while continuing to hope for his conversion^[54] — a sign that, for the Pietist Protestant as for the Jewish philosopher, mutual intellectual respect in no way erased the conviction that the religious question remained, in the last instance, decisive.

The genesis: the preface to Manasseh ben Israel and the excommunication affair

In 1782, Mendelssohn published a preface to the German translation of a 17th-century text, the Vindiciae Judaeorum ("Defense of the Jews") by Manasseh ben Israel^[55]. There he took a bold position for the time: he denounced the right of excommunication (cherem) still claimed by many rabbis, asserting — in a manner disputed, moreover, by rabbinic scholarship — that this practice did not belong to ancient and original Judaism but had been borrowed, over time, from Christianity^[56]. This stance, perceived by some as an attack on rabbinic authority, earned him an accusation by an anonymous author of undermining an essential element of the Mosaic Law^[57]. It was in response to this accusation that Mendelssohn wrote, the following year, his great treatise Jerusalem, oder über religiöse Macht und Judentum^[58].

The State commands, religion persuades

Jerusalem is divided into two parts: the first sets out a general theory of freedom of conscience and of the relations between State and religion; the second applies this theory to the defense of Judaism. Dialoguing at a distance with Hobbes and Locke, Mendelssohn contests the Hobbesian assimilation of right to mere force — "force and right are therefore two different things"^[59] — and, while sympathetic to the Lockean defense of tolerance, he goes beyond its limits by rejecting the overly sharp separation between temporal well-being and eternal felicity that Locke presupposes. His central formula, which has become classic, sums up the whole project:

"The State gives orders and coerces; religion teaches and persuades." — Moses Mendelssohn, Jerusalem, or On Religious Power and Judaism, 1783^[60]

For Mendelssohn, neither the State nor any religious institution holds the right to coerce the conscience of another: civil power disposes of physical coercion to ensure public order, but religious truth can only be proposed through teaching and persuasion, never imposed by force.

"A revealed legislation, not a revealed religion"

The second part of Jerusalem defends a philosophically bold thesis on the nature of Judaism itself:

"Judaism boasts of no exclusive revelation of eternal truths indispensable to salvation, of no revealed religion in the sense in which the term is usually understood. One thing is revealed religion, another thing is revealed legislation." — Moses Mendelssohn, Jerusalem, or On Religious Power and Judaism, trans. Allan Arkush, Brandeis University Press, 1983^[61]

According to Mendelssohn, the fundamental religious truths — the existence of God, providence, the immortality of the soul — are accessible to all human reason, Jewish or not, through philosophical reflection alone, independently of any particular revelation. What distinguishes Judaism, then, is not the exclusive possession of salvific truths inaccessible otherwise, but the reception of a legislation — a body of ritual, ceremonial and moral commandments — revealed to Israel at Sinai to regulate a particular way of life, without claiming doctrinal universality^[62].

A mixed reception: Kant applauds, the rabbis worry

The work aroused immense resonance. Kant himself, in a letter dated 16 August 1783, is said to have described Jerusalem as an "irrefutable book", praising the wit, subtlety and sagacity of its author, and hailing his ability to unite with his religion a degree of freedom of thought that one would hardly have believed possible and of which no other religion could then boast^[63]. Conversely, several contemporary Jewish thinkers and rabbis criticized Mendelssohn's rationalization of Judaism and his denial of the traditional right of excommunication, fearing that such a reduction of Jewish specificity to law alone would open the way to assimilation — a fear that Mendelssohn's own family posterity, as will be seen, would alas only confirm^[64].

A bridge to German culture

Between 1780 and 1783, Mendelssohn published his most enduring work for the history of European Judaism: a German translation of the Pentateuch, printed in Hebrew characters and accompanied by a commentary in Hebrew^[65], formally entitled Sefer Netivot ha-Shalom ("Book of the paths of peace") and commonly known as the Bi'ur ("the Explanation")^[66]. The project pursued a dual aim: to offer young German-speaking Jews direct and faithful access to the sacred text, and to provide them, through this translation, with an instrument for learning literary German that would open the way to general European culture^[67]. The familiar biblical text thus became, in the formula consecrated by historians of the Haskalah, the "bridge" by which ambitious young Jews passed into the great world of secular learning^[68].

Solomon Dubno and the collective work

The commentary, conceived as a grammatical and literal exegesis intended to counter the traditional homiletic method of rabbinic commentaries, was a collective work: Mendelssohn personally wrote the first six chapters of Genesis and most of Exodus, while his disciple Solomon Dubno — the most important collaborator on the project — and several other pupils took charge of the other books^[69]. This enterprise belongs to the broader movement of the "Biurists", who would make the Bi'ur and its commentary the true founding textbook of the Haskalah.

The 1779 ban and its mixed aftermath

From the appearance of the first fascicles, the translation aroused the hostility of several rabbis of the traditional school^[70]. In June 1779, a group of rabbis — among them Raphael Cohen of Hamburg, Ezekiel Landau of Prague, Hirsch Janow of Posen and Phineas Levi Horowitz of Frankfurt am Main — pronounced a ban against "the German Pentateuch of Moses of Dessau"^[71]. The grievances concerned the use of German rather than traditional Yiddish, the introduction of a philosophically styled commentary, and the fear that time devoted to learning German grammar would divert children from the study of the Torah^[72]. History will however retain an important nuance, revealing the complexity of this controversy: it is generally accepted that Landau himself — who died in 1793 — did not personally enforce this ban, and his own son Samuel, who succeeded him as rabbi of Prague, figures moreover among the subscribers to the work^[73].

The last great philosophical sum

Mendelssohn's last work published during his lifetime, Morgenstunden, oder Vorlesungen über das Daseyn Gottes ("Morning Hours, or Lectures on the Existence of God", Berlin, 1785), is the most accomplished exposition of his metaphysics and epistemology, placed entirely at the service of a rational demonstration of the existence of God^[74]. The work begins with general epistemological questions, moves through the existential importance of belief in God, in providence, and in immortality for human happiness, and culminates in a two-stage formal demonstration^[75].

The proof from sufficient reason and the ontological proof

The first proof starts from the principle of sufficient reason applied to every contingent thing: since I exist, and my contingent existence requires a sufficient cause which cannot itself be infinitely contingent, there must exist a necessary being grounding the entire chain of causes — a formula the tradition sums up as "I am, therefore God exists"^[76]. The second proof, of the ontological type, starts from the analysis of the very concept of God as a perfect being: a perfect being cannot be merely possible; it must be necessary, hence real^[77]. A notable fact in the history of philosophy: barely four years after the publication of the Critique of Pure Reason, Mendelssohn offers a careful refutation of the Kantian critique of the ontological proof — Kant having objected that existence is not a predicate capable of adding a real perfection to a concept. Mendelssohn replies that existence "emerges in each of us in a universal manner, not further analysable"^[78].

"The Cause of God": providence and corrective, not eternal, punishment

In an earlier work devoted to theodicy, Sache Gottes, oder die gerettete Vorsehung ("The Cause of God, or Providence Vindicated"), a critical reworking of the Latin abridgement of the Leibnizian Théodicée known as Causa Dei, Mendelssohn formulates one of his sharpest disagreements with his own master Leibniz: whereas the latter admitted, even in the "best of all possible worlds", that most human souls were destined to eternal damnation, Mendelssohn maintains that all posthumous punishment must be corrective and temporary, never definitive^[79]. This divergence, noted by several specialist surveys of Mendelssohnian thought, illuminates a constant trait of his philosophical theology: the rationalist conviction that divine goodness and wisdom exclude any punishment without proportion or corrective purpose — a position which, as will be seen, departs markedly from the Catholic doctrine of freely incurred eternal punishment.

The secret revealed by Jacobi

After Lessing's death in 1781, Mendelssohn planned to write a biographical essay in tribute to his friend. It was then that the philosopher Friedrich Heinrich Jacobi sent him a revelation presented as confidential: a few months before his death, Lessing had allegedly confided to him that he knew of no true philosophy apart from that of Spinoza — the famous hen kai pan ("one and all")^[80]. Such a confession, at a time when Spinozism remained synonymous with scandalous atheism and pantheism, called into question the posthumous reputation of the great dramatist. The private disagreement between Jacobi and Mendelssohn over the exact interpretation of this confession degenerated into a public controversy when, in 1785, Jacobi published their correspondence without Mendelssohn's consent under the title On the Doctrine of Spinoza, in Letters to Mr Moses Mendelssohn^[81].

The desperate defence and death

Shaken both personally and intellectually by this controversy touching the memory of his late friend, Mendelssohn hastily wrote a final text, An die Freunde Lessings ("To Lessing's Friends, an Appendix to Mr Jacobi's Correspondence on the Doctrine of Spinoza"), completed in the very last days of his life and published at the beginning of 1786^[82]. According to the traditional account, popularised during his own lifetime, Mendelssohn is said to have caught cold carrying his manuscript to the publisher himself on an icy night of New Year 1786, having forgotten his coat in his haste; he died four days later, on 4 January 1786, in Berlin, at the age of fifty-six^[83]. Several of his contemporaries, including Johann Gottfried Herder, would hold Jacobi partly responsible for this premature death, so heavily had the intellectual harassment he had inflicted on Mendelssohn over Lessing's memory weighed on his already fragile health^[84]. He is buried in the old Jewish cemetery on Große Hamburger Straße in Berlin, beneath an epitaph designating him as "the sage Reb Moses of Dessau"^[85].

"The Martyr of Reason" — title of an essay devoted to Mendelssohn, Jewish Review of Books^[86]

This title, given retrospectively by the Jewish Review of Books to an essay on the last months of his life, aptly sums up how posterity has read this ending: Mendelssohn died literally exhausted by his fight to defend, to the very end, rationality and his friend's honour against the charge of pantheistic irrationalism.

A character modelled on a living friend

In 1779, two years before his death, Lessing published his most famous drama, Nathan der Weise ("Nathan the Wise"), whose title character — a wise, generous, and tolerant Jewish merchant of Jerusalem — was very widely recognised by contemporaries as a faithful portrait of Mendelssohn himself^[87]. The two men moreover shared a common taste for chess, which Lessing symbolically lends to Nathan and to Sultan Saladin, brought together around a chessboard in the play^[88]. Lessing's choice to write so explicitly about religious tolerance owes much, according to historians of German literature, to his repeated conversations with Mendelssohn and to the lived experience of their Judeo-Christian friendship in Enlightenment Berlin^[89].

The parable of the three rings

At the heart of the play, Nathan answers a trap question from Sultan Saladin — which is the true religion, among Judaism, Christianity, and Islam? — with the famous parable of the three rings: a father owned a magic ring, handed down from generation to generation to the most beloved son; having three sons whom he loves equally, he has two copies made perfectly identical to the original and gives one ring to each in secret, so that none can know with certainty whether he holds the genuine ring. The parable's conclusion invites each heir to prove, through a virtuous life, that he bears the genuine ring — shifting the question from doctrinal truth to moral conduct. This parable sums up what commentators call Mendelssohn's pragmatic principle of the possible plurality of truths: just as different nations may need different constitutions, different individuals — and, by extension, different peoples — might need different religions, without any of them being able to claim an exclusive and demonstrable monopoly on religious truth^[90].

Six children, four different paths

Mendelssohn and Fromet Gugenheim had ten children, six of whom reached adulthood. The following table summarises their religious fate, as now established by historiography:

Of the six children who reached adulthood, therefore, only Joseph and Recha remained faithful to Judaism; the other four, to varying degrees and by different paths, joined Christianity — two Protestantism, two Catholicism^[98].

Dorothea, from Berlin to Rome

The eldest daughter, Brendel — who in 1794 took the first name of Dorothea — followed the most spectacular path. Married first to the banker Simon Veit, she divorced in 1799 to marry the Romantic writer Friedrich Schlegel. She first converted to Protestantism in 1804, then to Catholicism in 1808, in Cologne, drawing her husband into the same movement of conversion, of which she was, according to biographers, the true driving force^{[99] [100]}. Her sister Henriette, at first so scandalised that she treated her as a pariah within the wider family, nevertheless joined her in Catholicism four years later, in 1812^[101]. Dorothea's son, the painter Philipp Veit, would himself become a fervent Catholic, of a neo-medieval sensibility^[102]. It was in this same Viennese Romantic circle, marked by the conversions of the Mendelssohn children, that the apostolate of Saint Clement Mary Hofbauer shone at the same period, whose dedicated Ignispedia article develops the influence he exercised over the Schlegels and over other figures of German Romanticism converted to Catholicism.

Abraham, Felix and the name of Bartholdy

The son Abraham, father of the future composers Fanny and Felix Mendelssohn Bartholdy, chose another path: converted to Reformed Protestantism with his wife Lea in 1822, he had his own children baptised as early as 1816, when Felix was only seven years old^[103]. The family then adopted the compound surname "Mendelssohn Bartholdy", borrowed from a property inherited from Lea's brother. In a letter addressed in 1829 to his son Felix, by then a famous composer, Abraham justified this choice by the desire for a decisive break with the religious heritage of his own father:

"There can no more be a Christian Mendelssohn than there can be a Jewish Confucius." — Abraham Mendelssohn Bartholdy, letter to his son Felix, 1829^[104]

This formula, almost cruel in its harshness towards the memory of the deceased philosopher, says enough about the depth of the disavowal which the next generation directed at the Mendelssohnian project of reconciling Judaism and modernity: rather than perpetuating a rationalised Judaism integrated into German culture, most of Mendelssohn's grandchildren chose simply to leave Judaism altogether. Felix Mendelssohn Bartholdy would nevertheless remain, all his life, conscious and proud of his ancestry and of his connection with his grandfather Moses^[105] — a sign that the Mendelssohnian identity, even disavowed on the religious level, continued to haunt the family memory.

Heinrich Heine's assessment

The poet Heinrich Heine, himself a Jew converted to Protestantism, would later offer a judgement on Mendelssohn's work that has remained famous, comparing him to Luther: by affirming the primacy of the translated Bible as the ultimate source of religion, Mendelssohn had, according to Heine, "overthrown the Talmud" and "shattered Judaic Catholicism"^[106] — a provocative formula which, beyond its Voltairean irony, aptly situates the revolutionary scope of the Mendelssohnian gesture within traditional rabbinic Judaism itself.

Natural theology: a shared project, distinct foundations

Mendelssohn's project — demonstrating by natural reason alone the existence of God, providence and the immortality of the soul, without ever renouncing fidelity to his particular religious allegiance — overlaps in many respects with that of Catholic natural theology as developed by the Thomist tradition: human intelligence, created by God and proportioned to truth, is capable, by its natural powers alone, of establishing with certainty the existence of a necessary being at the origin of all contingent reality. The Catechism of the Catholic Church recalls this constant conviction of the Magisterium: "Holy Mother Church holds and teaches that God, the first cause and the last end of all things, can be known with certainty from the created world by the natural light of human reason" (CCC § 36). On this ground, Mendelssohn's first proof — the argument from sufficient reason applied to the contingency of all existence — rejoins, in its logical structure if not in its technical detail, the third of the Five Ways of Saint Thomas Aquinas, the one which starts from the contingency of the things of the world to conclude to a being necessary in itself.

On the ontological proof, by contrast, the Thomist tradition proves closer to Kant than to Mendelssohn — for reasons, however, radically different from those of the philosopher of Königsberg. Long before Kant, Saint Thomas Aquinas had already set aside the a priori argument of Anselmian type according to which God's existence would be known as self-evident as soon as one understands the meaning of the word "God":

"It does not follow that he understands that what the word signifies exists really (in reality), but only that it exists in the mind (in the intellect). And it cannot be maintained that it exists really, unless one admits that there really exists something such that nothing greater can be thought — which is precisely what those who hold that God does not exist do not admit." — Saint Thomas Aquinas, Summa Theologiae, Ia, q. 2, a. 1^[107]

For Thomas as for Kant, existence is not deduced analytically from a mere concept, even that of a perfect being — but whereas Kant concludes from this that every rational proof of God, including the cosmological one, remains ultimately invalid, Thomas Aquinas draws the opposite conclusion: it is precisely because the a priori argument fails that one must take the a posteriori path, which starts from sensible effects (motion, causality, contingency, degrees of perfection, finality) to ascend to their first cause — the Five Ways of the Summa Theologiae (Ia, q. 2, a. 3). Mendelssohn, in defending against Kant a reformulated version of the ontological proof while developing in parallel his own cosmological proof from sufficient reason, thus occupies a singular position: closer to Thomas than to Kant on the very possibility of a rigorous natural theology, but closer to Anselm than to Thomas on the validity of the ontological argument itself.

Freedom of conscience without indifferentism: from Mendelssohn to Dignitatis Humanae

Mendelssohn's demand for a freedom of conscience protected from all state or ecclesial coercion finds, in later Catholic teaching, an echo that should not be underestimated. The Second Vatican Council, in its declaration Dignitatis Humanae on religious liberty, indeed proclaims:

"This Council declares that the human person has a right to religious freedom." — Second Vatican Ecumenical Council, declaration Dignitatis Humanae, 7 December 1965, § 2^[108]

This right, the conciliar text specifies, rests on "the very dignity of the human person as made known by the Word of God and by reason itself"^[109] — a twofold, revealed and rational source which is not without recalling the Mendelssohnian approach of grounding tolerance both in principles of natural reason and in fidelity to one's own religious tradition. But the Council is careful to specify immediately the limits of this proclamation:

"[This right] leaves untouched traditional Catholic doctrine on the moral duty of men and societies toward the true religion and toward the one Church of Christ." — Second Vatican Ecumenical Council, declaration Dignitatis Humanae, 7 December 1965, preamble^[110]

It is precisely on this point that Catholicism parts company with the conclusion to which Mendelssohn, via the parable of the three rings popularised by Lessing, leaves the reader: the pragmatic principle of the plurality of truths, according to which different peoples might legitimately need different religions without any of them being able to claim truth exclusively. The Catholic Church defends a civil right to religious liberty — no one should be forced by coercion to profess a faith against his conscience — without ever renouncing the affirmation that Christ is the one and full revelation of God to men, and that religious truth, far from being plural or relative to nations, is one and universal. The freedom of conscience which Mendelssohn defended against civil or ecclesial coercion thus rejoins, on the practical and political level, an intuition which the Church eventually made its own in the twentieth century; but the doctrinal indifferentism illustrated by the parable of the three rings — the idea that no ring is objectively the true one, or that the question itself has no decidable meaning — remains foreign, indeed opposed, to the Catholic faith in the uniqueness of the salvation offered in Christ.

Nostra Aetate and esteem for Mendelssohn's Jewish heritage

On the level of the esteem borne for the spiritual heritage of the Jewish people, of whom Mendelssohn remains one of the great modern figures, the Catholic Church likewise renewed its outlook at the Second Vatican Council. The declaration Nostra Aetate affirms:

"The Church of Christ (...) acknowledges that the beginnings of her faith and election are found, in accordance with the divine mystery of salvation, in the patriarchs, Moses and the prophets (...) [She] deplores hatreds, persecutions and manifestations of antisemitism, which, whatever their time and authors, were directed against the Jews." — Second Vatican Ecumenical Council, declaration Nostra Aetate, 28 October 1965, § 4^[111]

This text, which explicitly calls for "mutual knowledge and esteem, which will arise above all from biblical and theological studies, as well as from fraternal dialogue"^[112], gives full meaning to the Catholic reading of Mendelssohn's work: that of a Jewish thinker whose struggle for the dignity of his tradition, for freedom of conscience and for the rational demonstration of God's existence deserves intellectual respect and fraternal esteem, without that esteem implying adherence to the relativistic conclusions which some of his readers, down to his own converted descendants, may have drawn — in one direction or the other — from his work.

What a Catholic retains — and what he cannot follow

Three legacies of Mendelssohn deserve to be retained without reservation by a Catholic reader: his tireless defence of freedom of conscience against all coercion, religious or state; his rationalist confidence in the capacity of human intelligence to demonstrate God's existence, even if its technical detail must be corrected in the light of Thomist natural theology; and his refusal, against Leibniz, of a God whose justice would accommodate massive and disproportionate damnation — a refusal which, on this precise point, invites the Catholic theologian to recall all the more carefully that the doctrine of hell, far from being an arbitrary disproportion, follows from absolute respect for human freedom before the offer of grace, and not from gratuitous divine severity. By contrast, the reduction of Judaism to a mere "revealed legislation" without binding doctrinal content, and the implicit conclusion of the parable of the three rings that the question of religious truth remains undecidable, cannot be followed by a faith which confesses, with the whole apostolic tradition, that "no one comes to the Father except through [Christ]" (Jn 14:6) — a truth which Nostra Aetate proclaims together with the most sincere esteem for the Jewish spiritual heritage of which Mendelssohn remains one of the greatest modern witnesses.

• On the medieval master whose philosophy was transmitted to Mendelssohn from childhood by Rabbi David Fränkel, see Maimonides (1138-1204).
• On the great biblical commentator whose exegetical work inspires, in its own way, the Bi'ur project, see Rashi (1040-1105).
• On the Pharisee master whose teaching of tolerance foreshadows, in a wholly different context, that of Mendelssohn, see Hillel the Elder (c. 110 BC–c. AD 10).
• On what the Catholic Church teaches today about Judaism, see Judaism.
• On the philosopher whose posthumous "confession" triggered, in spite of himself, the battle that cost Mendelssohn his life, see Baruch Spinoza (1632-1677).
• On the Redemptorist priest who accompanied, in Vienna, several conversions in the Romantic circle frequented by Mendelssohn's own daughter, see Saint Clement Mary Hofbauer.