According to Daniel B. Schwartz in his study of The First Modern Jew – the historian is referring to Baruch Spinoza as that trailblazer – he discusses the descendants of German-Jewish philosopher Moses Mendelssohn, who was influenced by the heretic of Amsterdam. “Of Mendelssohn’s six children,” Schwartz writes, “four converted [to Christianity], all following their father’s death in 1786. Of his grandchildren, only one went to his grave as a Jew.”Was Mendelssohn’s philosophy responsible for the conversions to Christianity of his descendants? The blame of the mass apostasy of Mendelssohn’s descendants does rest, for some, on his philosophy. There is precedent for this assessment in the work of historian Yitzhak “Fritz” Baer in his dichotomy between Sephardi and Ashkenazi Jews. Baer, a German Jew who made his mark of brilliance at Hebrew University in Jerusalem, blamed the conversion of Jews to Catholicism in Spain on their study of Aristotelian philosophy which, the historian believed, weakened their spiritual resolve. This was opposed to the Talmud-centered folk piety of medieval Ashkenazi Jews who chose martyrdom rather than conversion.Many centuries before Baer in Muslim Spain, Hebrew poet Judah Halevi argued in his Kuzari that Revelation as an historical event dispensed with the need to reconcile Torah and Aristotle. But one could argue that Moses Mendelssohn was not Moses Maimonides, that 18th century Berlin was not medieval Cairo, and that the attempt by Mendelssohn to confront Kant led to a Jewish crisis worse than the Jewish struggle over Rambam’s philosophical works. For an early modern thinker like Catholic theologian and mathematician Blaise Pascal there was only one choice: “Not the God of the philosophers but the God of Abraham, Isaac, and Jacob.”But that is only part of the picture. While Mendelssohn’s philosophy was certainly the outcome of a confrontation with the German Enlightenment, it was not a radical rejection of Judaism – in fact, it was an heroic defense of the Jewish faith – and Mendelssohn remained an observant Jew his whole life. His classic work of Jewish philosophy, Jerusalem (1783), is conservative and careful and a far cry from the pantheism of Spinoza. In this work, Mendelssohn argues that Kant and the German Enlightenment’s understanding of Judaism are warped. Rather than viewing Judaism as coercive laws and superstitions that in no way elevates the individual morally, ethically or spiritually, Mendelssohn argues that it is Judaism that is a “revealed legislation” and not a “revealed religion.”Mendelssohn is no atheist and, in fact, he argues that Judaism is the epitome of the “Religion of Reason,” purged of the dogma and superstition that dominated Christianity.He is on the mark despite the fact that he reinterprets the nature of Revelation in a way that would not please traditionalists.Mendelssohn seems to neutralize that nature of the Covenant based on the relationship between God and God’s Chosen People. Still, he argues against religious coercion and for religious tolerance and is brave enough to confront those who would demean Judaism – and he would defend Judaism against Christianity. I do not see, at first glance, how this would lead to apostasy. It seems just the opposite.A more cogent argument is a social one.Mendelssohn’s involvement in Prussian society, being dubbed the “German Socrates,” broke down the barriers which for centuries separated Jews from the non-Jewish majority. Mendelssohn’s acceptance by the German Enlightenment – and especially by his close friend G.E. Lessing – integrated the Jewish philosopher into a modern world he would not have know of had he been born 50 years earlier. The pressure on Mendelssohn by Christians to convert was intense and he had the fortitude to reject these calls. His children did not have that fortitude.Under the pressure of Prussian society they were unable to resist the temptation to abandon their father’s modern approach to Revelation and instead abandoned Judaism.Indeed, as described by historian Daniel B.Schwartz, in the period in Berlin from 1750 to 1830 there was a wave of Jews who converted to Christianity. Among Berlin’s Jewish elite there was an “epidemic of baptism.” Heinrich Heine, born a Jew, the greatest German lyric poet of the 19th century, converted to Lutheranism, in part for professional reasons.Throughout Germanic lands baptism was required to teach in universities or gain a professional position in the law. While I came down hard on Rachel Varnhagen and her salon that brought together Jews and Christians in the elite, my harshest criticism was that after her conversion she seemed to embrace a sincere Christianity. But for Jewish converts like Heine, baptism opened doors of opportunity that were closed for Jews. So “the epidemic of baptism” could have little to do with religious faith and much to do with Jews achieving success in Berlin in that period of discrimination.Still, the conversions do not only have their roots in Jews getting ahead in Christian society. For many of the Jewish elite in Berlin the embrace of Christianity was an act of religious and intellectual conviction. Abraham Mendelssohn – a son of the great philosopher – and a deist and rationalist, raised his children as Lutherans. In a July 1820 letter to his daughter, Abraham Mendelssohn seemed to both reject the influence of the legacy of his own father but also seemed to follow in a logical path of conversion where the philosopher could lead the Jew: “The outward form of your religion your teacher has given you is historical, and changeable like all human ordinances.Some thousands of years ago the Jewish form was the reigning one, then the heathen form, and now it is the Christian. We, your mother and I, were born and brought up by our parents as Jews, and without being obliged to change the form of our religion have been able to follow the divine instinct in us and in our conscience. We have educated you and your brothers and sister in the Christian faith, because it is the creed of most civilized people, and contains nothing can lead you away from what is good, and much that guides you to love, obedience, tolerance, and resignation, even if it offered nothing but the example of its founder, understood by so few, and followed by still fewer.”Heinrich Heine writes that “the baptismal certificate is the ticket of admission to European culture.” This indicates that the worldview of Abraham Mendelssohn, Rachel Varnhagen and Heine was rooted in the inferiority of Judaism to German culture. Heine’s conversion to Lutheranism was not simply practical but psychological.Heine, in an early poem, equated Judaism with disease. This was not the outlook of Moses Mendelssohn – he was raised in an observant environment with exposure to the great works of Jewish literature and theology.For Mendelssohn’s son to explain that Judaism was only relevant 2,000 years ago and that one could reach goals of spirituality and ethics in the Christianity of the Enlightenment is an insult to his father’s faith. The argument for tolerance of all religion does not mean that all religions are equal. There is a rich heritage of Jewish polemics throughout the ages that argued for the superiority of Judaism. To understand the fundamental principles of Christianity and Islam in no way levels the playing field. The deists were wrong: Yahweh is not Christ is not Allah.While Abraham Mendelssohn certainly did not understand the “founder” of Christianity as a Son of God in a way a traditional Lutheran would understand, there is no doubt that his father’s philosophy of tolerance for all religion weakened his son’s perception that Judaism was still a vital faith and Christianity stood in opposition based on detail and dogma. G.E. Lessing, a close confidante of Moses Mendelssohn, expresses the equality of all religion as emanating from one source in his play praising his Jewish friend titled Nathan the Wise (1779). Mendelssohn believed in separation of church and state and emancipation.At a time when the greatest German Enlightenment philosopher, Immanuel Kant, was discussing the euthanizing of Judaism as an outmoded and unethical superstition, Moses Menddelssohn spoke out bravely for the integrity of Judaism in the world of the European Enlightenment.But his break with Jewish theology and tradition as understood by Jews living apart from non-Jews in the ancient and medieval world – and their belief that their faith was divine in origin and their religion superior to other faiths – created a slippery slope from which Modern Judaism would not recover.Have Jews died with the Shema on their lips because a God of Reason revealed “legislation” to them on Mount Sinai? Was Judah Halevi right? Perhaps, the national and historical experience at Sinai was not a rational experience that needs to be reconciled with Athenian or Kantian or Hegelian philosophy. This is not to negate the great tradition of Jewish philosophy and its confrontation with the surrounding world. But “divine legislation” is sterile and banal and will only inspire the elite of the Haskala. Or in the case of the German Enlightenment lead Jews away from Judaism.That his children and his followers interpreted his words in their own way – often at odds with traditional Judaism, even embracing apostasy – does not mean that there were many other social and psychological factors that weakened the resolve of the Jews of Berlin. In Jerusalem, the philosopher stated: “Adapt yourselves to the morals and the constitution of the land to which you have been removed; but hold fast to the religion of your fathers.” It seems too often in the modern Diaspora that Mendelssohn’s call for integration into non-Jewish society far outweighs “holding fast” to 3,500 years of profound texts and traditions.(The text of Abraham Mendelssohn’s letter to his daughter can be found in The Jew in the Modern World: A Documentary History edited by Paul Mendes-Flohr and Jehuda Reinharz, Second Edition.) The author is rabbi of Congregation Anshei Sholom in West Palm Beach, Florida.