Fantasies of lost wholeness are one of the symptoms of modernity. The 19th century saw the rise of an epidemic of nostalgia, in which the dislocations of the modern world—capitalism, industrialism, secularism, urbanization—produced a longing to return to a vanished moment when there were no divisions, when society and human life were still whole. Many different pasts seized the imagination of the homesick present. For the French philosopher Jean-Jacques Rousseau, it was the state of nature, before civilization even began; for the German art historian Johann Joachim Winckelmann, it was ancient Greece, whose art spoke of a lost simplicity and calm; for the English reformer John Ruskin, it was the Middle Ages, whose Gothic cathedrals were monuments to a time when labor was unalienated. The details mattered less than the belief that sometime, somewhere in the past, human beings were happier and more complete than they are today.Modern Jews are not immune to this kind of nostalgia; but as so often happens, the Jewish case is different and more complicated. At the beginning of her superb and thought-provoking new book, How Judaism Became a Religion: An Introduction to Modern Jewish Thought (Princeton), Leora Batnitzky explains that modern definitions of Jewishness are inescapably divided and partial. She begins: “Is Judaism a religion? Is Jewishness a matter of culture? Are the Jews a nation? These are modern questions.” But there was a time, “prior to modernity,” she continues, when “Judaism and Jewishness were all these at once: religion, culture and nationality.” Until the 18th century, the question of how to define Jewishness never arose, because Jews lived in a wholly Jewish world. A Jewish community was made up exclusively of Jews, lived by Jewish law, prayed according to Jewish ritual, and even had a large degree of political autonomy—it could levy its own taxes, appoint its own officials, and punish lawbreakers. Each community, Batnitzky writes, enjoyed this wholeness, and together they formed an even larger whole: “Premodern Jews imagined themselves as one united people, as klal Yisrael, ‘the collective people of Israel.’ ”For Batnitzky, too, modernity is the age of fracture, when this ostensible wholeness and unity began to come apart. This began in Western Europe with the French Revolution, which introduced the principle that Jews should not be viewed as members of an autonomous community but as individual citizens in a secular nation-state. As one French statesman put it: “One must refuse everything to the Jews as a nation but one must give them everything as individuals.” This principle spread with Napoleon’s rule to Germany, where the substantial Jewish population became a test case for the possibility of true emancipation in an anti-Semitic society.For these German Jews, who make up the focus of the first half of Batnitzky’s book, the age of lost wholeness was too close to be the source of comfortable nostalgia. It was too close in time—the most assimilated German Jewish families were only a generation or two removed from the ghetto—and too close in space: Just over the German border to the east lay Poland and Russia, the Jewish heartland, where millions of Jews lived traditional lives and labored under bitter government persecution. The only way out, for these emancipated Jews, was forward. But if Jewishness was no longer an all-encompassing identity, no longer the name of a world, what could it be?Batnitzky’s answer is given in her title. Judaism became a religion, she argues, when it stopped being a civic and political identity. Religion was the name of the shrunken sphere of life that Jewishness was allowed to occupy in the modern world. In particular, Batnitzky argues, German Jews began to think about Judaism in terms borrowed from Protestantism, as a private faith whose most important dimensions were emotional and ethical.The problem, of course, is that this understanding of religion manifestly clashes with rabbinic Judaism as it had evolved over the centuries. Rabbinic Judaism, as expressed in the Talmud and many later commentaries and codes of law, was above all a religion of practice, of public and communal life. Every area of a Jewish life was regulated Jewishly, from sexual relations to diet to tort law. Yet these were exactly the things that, in the modern world, were meant to be governed by the nation-state and by a common, secular culture. How could Judaism’s all-encompassing legacy be squeezed into the small compartment designated for religion?The first four chapters of How Judaism Became a Religion are devoted to the ways major German Jewish thinkers tried—and, in Batnitzky’s view, largely failed—to answer that question. She begins, inevitably, with Moses Mendelssohn, the 18th-century philosopher who is remembered as the first modern Jew, in large part because he was accepted as an equal by Gentile thinkers such as Lessing and Kant. In his 1783 book Jerusalem: Or on Religious Power and Judaism, Mendelssohn, an Orthodox Jew, argued that—in Batnitzky’s words—“Judaism … is not concerned with power and therefore does not conflict with the possibility of the Jewish integration into the modern nation state.” Equally important, as Batnitzky writes of Mendelssohn’s case, Judaism does not possess a creed to which every believer must adhere, the way Christianity does. Instead, it possesses “divine legislation—laws, commandments, ordinances, rules of life,” which the Jew can follow without prejudice to his citizenship in the German state.There is, however, a fairly obvious contradiction between the two premises of Mendelssohn’s argument. If Judaism is a religion of legislation, of behavior rather than belief, how could it not conflict with the legislation and custom of the wider Christian society? Or, to put the question another way: What compels the Jew to keep practicing Jewish law, living a Jewish life, once the possibility of assimilation opens up? “Mendelssohn offers no philosophical or theological justification for why Jews should obey the [Jewish] law,” Batnitzky writes. Personally, he would find it possible to be at the same time an enlightened philosopher and an observant Jew; but all of his grandchildren would end up converting to Christianity.Continue reading: Zionism arisesIn the following chapters, Batnitzky takes up the efforts of later Jewish thinkers to square this circle. Abraham Geiger, the founder of the Reform movement, would double down on the idea of Judaism as a “religion,” a private ethical creed, and would jettison almost all of traditional Jewish practice. In response, Samson Raphael Hirsch would insist on the continuing urgency of Jewish law—“To be a Jew is not a mere part, it is the sum total of our task in life”—and thereby found the Orthodox movement. Batnitzky usefully reminds us that Orthodoxy itself, as we now understand it, is a modern phenomenon, a response to exactly the same cultural fissures that produced Reform and Conservative Judaism. Later thinkers, including Martin Buber and Franz Rosenzweig, would find their own, often idiosyncratic solutions to the problem of what remains of Judaism once it is reduced to a religion.In the second half of How Judaism Became a Religion, Batnitzky leaves behind the rather rarefied precincts of German Jewish philosophy and theology and turns to the experience of modern Eastern European Jews. German Jewry tends to loom large in modern Jewish history, because it was in many ways the laboratory for Jewish assimilation and because it produced a sophisticated, highly self-conscious literary and intellectual response to assimilation’s problems. (Its tragic end, of course, only heightens the ironic power of those responses.)But in numerical terms, the Jews of Eastern Europe vastly outweighed the Jews of Western Europe; and their situation was much different from that faced by Mendelssohn’s heirs. In the West, the problem was how to maintain a Jewish identity in the face of the temptation to assimilate. In the East, the problem was how to survive in an environment of increasing poverty and persecution. Historically, the two great answers to that question were Zionism and emigration to the United States. Those were the only solutions that survived the Holocaust, which annihilated the Jewish heartland in Eastern Europe.But Batnitzky is more interested in the solutions that emerged in Eastern Europe before the Holocaust—experiments in Jewish identity that never permanently succeeded or failed, because they were violently cut short. What these solutions have in common is suggested by the heading of the second part of her book: “Detaching Judaism from Religion.” By this, she means detaching it from the narrow, Protestant definition of religion that predominated in Germany—not rejecting religious belief and practice altogether. On the contrary, Batnitzky devotes one chapter to 19th-century Jewish revival movements like Hasidism and the ethically strenuous Mussar school. Though these movements were historical antagonists, Batnitzky argues that they had in common a new emphasis on the individual. They attempted to enrich the believer’s experience of Jewishness in ways that were foreign to traditional rabbinical Judaism.For other Eastern European Jews, the way forward led not through religion but through culture. In a chapter on modern Yiddish literature, Batnitzky shows how writers like Mendele Mokher Sforim and Sholem Aleichem tried to create a new, essentially secular Jewish culture on the foundation of traditional Judaism: “Modern Yiddish literature both creatively described eastern European Jewish life as its denizens experienced it and … transforms what had formerly been theological categories into cultural ones.” Yiddishism often went hand in hand with militant socialism and atheism, and Batnitzky raises the question of whether a Jewish culture could have long survived after being cut off from its religious roots. But the experiment was a brave one, and it left behind a major body of imaginative literature that is practically all that survives of Eastern European Jewish life.Finally, and most momentously, there was Zionism. Zionism can be seen as a response to the failure of both Western and Eastern European attempts to adjust Judaism to modernity. In the West, the promise of assimilation had proved a false one, as anti-Semitism seemed to grow, rather than shrink, with time. Theodor Herzl, the Viennese journalist who became the unlikely founder of the Zionist movement, was radicalized by his experience reporting on the Dreyfus Affair in France. After seeing mobs of Parisians shouting “death to the Jews”—this in the city that was the capital of the European Enlightenment, in the country that was the first to emancipate the Jews—Herzl decided that the only solution for Jews in Europe was to escape and start over in Palestine. Meanwhile, the increasing pressure on Russian Jews after 1881, as the tsar ramped up economic and political persecution, led to both a mass emigration to America and an increasing enthusiasm for Zionism.Batnitzky treats all this in a chapter titled “The Rejection of Jewish Religion and the Birth of Jewish Nationalism.” This rather combative title points to an ambiguity at the heart of Zionism, which she formulates simply: “What is Jewish about the Jewish state?” To Herzl, who was completely assimilated and knew next to nothing about Judaism, Zionism was a national liberation movement in the 19th-century style, not a return to the Holy Land or a renaissance of Jewish culture. To Ahad Ha’am, the great theorist of cultural Zionism, it was the reverse: The achievement of Jewish statehood meant less to him than a revival of Jewish spirit and mind. Yet even Ahad Ha’am was a post-religious thinker, and he wrestled with the problem of how to relate Jewish culture to Jewish religion. Zionism, no less than Reform Judaism and Yiddish culture, was an attempt to give Jewishness a new meaning in a world where its old, comprehensive, unproblematic meaning had collapsed.***All of the figures we meet in How Judaism Became a Religion are philosophers, writers, and political theorists. Yet as Mitchell B. Hart points out in the introduction to Jews and Race: Writings on Identity and Difference, 1880-1940 (Brandeis), to define “modern Jewish thought” in this way is to omit a great deal. “Are philosophy and theology necessarily more important and of more lasting interest and value than anthropological, biological, or social scientific thought?” Hart asks. When modern Jews thought about Jewishness, were they always thinking in terms of religion and culture—or were they thinking, often enough, about race?Continue reading: Jews and RaceThere is something automatically disturbing about any linkage of the words “Jews” and “race,” as Hart knows full well. Along with Africans, Jews are the group that suffered most from the Western obsession with race and racism. Reading any specimen of 19th- and early 20th-century “race science” fills the Jewish reader with dread, knowing that this kind of thinking culminated in the Nazi fetish for racial hygiene, in the Nuremberg laws and the death camps.Yet Hart reminds us that during the very period Batnitzky identifies as the seedbed of “modern Jewish thought,” racism—or, if we want to avoid the pejorative connotations of that word, race-ology—was a staple of intellectual discourse. In retrospect, it is easy to see that race-ology was a classic pseudoscience, based on prejudice and assumption, making unfalsifiable claims, and shot through with chauvinism and bigotry. But at the time, most people sincerely believed in the existence and importance of human races, and intellectuals devoted a good deal of effort to identifying, analyzing, and ranking races. And this included many Jews.In Jews and Race, published as part of Brandeis’ exciting new Library of Modern Jewish Thought, Hart has gathered 36 original documents—studies, scientific articles, and popular essays. It would have been easy to fill such a book with anti-Semitic writings, convinced of Jews’ racial inferiority, but that is not Hart’s mandate. On the contrary, almost all of the pieces in the book were written by Jews, and their approach ranges from the “objective” to the frankly apologetic. The goal of these writers was to use race science to answer the very question that Batnitzky’s philosophers posed: What remains of Jewish identity in the modern world?Race seemed to offer a convenient answer to this question. In an era when science was becoming, as it remains today, the supreme authority, the definer of what is really real, it was tempting to forge an alliance between science and Jewishness. After all, if Jewishness was a biological identity, rather than a religious or cultural one, then there was no need to worry about authenticity or assimilation: One’s “germ plasm” could not convert to Christianity. Klal Yisrael may have been fracturing, but race offered a still deeper kind of Jewish unity.But as Jews and Race demonstrates, there were two major problems with redefining Jewishness as a race. The first was the deeply unscientific nature of race science: This was a field in which terms had no fixed meaning and data were haphazard or nonexistent. The unempirical nature of the whole enterprise can be seen by the general agreement among the contributors to Jews and Race that marriages between a Jew and a Gentile tend to be infertile—a patently absurd “finding” that is clearly based in racial ideology, not fact. And it gets worse: Ignaz Zollschan, an Austrian physician, was of the opinion that “half-breeds who are the offspring of widely different races have a bad reputation in respect to character.”If such pernicious absurdities are accepted as obvious truths, it is no wonder that race theorists couldn’t agree on even the most basic terminology. Are Jews a race? Are they a “pure” race, or a mixture of Semitic, Hittite, and other stocks? What about the difference between Ashkenazi and Sephardic Jews—does this constitute a racial distinction in itself? One apparently “scientific” way of approaching the question is by measurement—of noses, skulls, lips. Thus the Jewish Encyclopedia of 1901, under the heading “anthropology,” notes: “The nose is generally considered the characteristic feature of the Jews, who have, on the average, the longest (77 mm) and narrowest (34 mm). … The lips of Jews are also characteristic, as large a proportion as 48 percent being thick. These features are the elements that go to make the marked Jewish type, which has been defined as ‘Semitic features with ghetto expression.’ ”But if this is the racial type, why do so many Jews look different? Is it because many Eastern European Jews are actually descended from the Khazars, a Crimean people who converted to Judaism in the dark ages? The poor Khazars are made to do a lot of explanatory work in Jews and Race, as are the biblical Amorites; both are posited as possible sources of blond hair and fair skin among the Jews.Behind the rhetoric of scientific objectivity, however, it is clear that the Jewish writers represented in Jews and Race are jealous of the honor of their people. Knowing that much racial discourse was profoundly anti-Semitic, they are united in their refusal to grant that any “negative” Jewish trait is racial—and thus, it would follow, unalterable. If epidemiology suggests that Jews are more prone to hemorrhoids and diabetes, various contributors write, that is because of their sedentary professions, not genetics. If, as the psychiatrist Abraham Myerson insists, there can be “no difference of opinion about the liability of the Jews to psychoneuroses,” that is a result of persecution and cramped living quarters, not mental frailty. When it comes to positive Jewish traits, on the other hand, the race can take credit: Jews are said to be immune to syphilis and alcoholism, and naturally long-lived, with what one writer calls “unprecedented tenacity of life.”The hidden logic of these debates is the principle Zollschan laid down in 1909: “It becomes a question of which of these possible deficiencies are ephemeral and which a product of the immutability of race, inherited in the blood, and inseparable from the blood. That is a question of immense significance. If it were to emerge that Jewish racial blood is inferior, then the disappearance of the race would be desirable.” Zollschan, who was an ardent Zionist, was convinced that “Jewish racial blood” was actually superior and needed to be guarded against contamination. But as time would show, this way of thinking proved to be a disastrously losing proposition for the Jews.Race, in the all-encompassing sense that these writers used it, is not a biological fact but a moral-social-intellectual construction, heavily freighted with value judgments. In any given society, those with the power to define race inevitably used it to their own advantage. In Nazi Germany, every positive racial attribute was assigned to Aryans and every negative one to Jews—with the corollary that, just as Zollschan wrote, “the disappearance of the race would be desirable.” It is no wonder that post-Holocaust Jewry, especially in America, would become leading opponents of racism and of the very notion that peoples can be ranked according to their worthiness to live. That every individual and every group has the right to life, that each makes an irreplaceable contribution to the world, is a central conviction of liberal thought today.In the end, neither the thinkers Batnitzky writes about nor the “thinkers” Hart has collected seem to match our current intuitions about what Jewishness is. It is not simply a religion—as we acknowledge every time we describe someone as a “nonobservant Jew.” And it is not an ethnicity, since we now strongly reject the idea that a biological fact has any ethical or political relevance. Yet both religion and ethnicity somehow do play a role in defining peoplehood, which may come closest to describing what Jewishness means today. More practically, the most reliable way of defining a Jew in the 21st century is that he is someone who worries about what it means to be a Jew in the 21st century. For such a person, both of these books offer fascinating and challenging reading.Adam Kirsch is a poet and literary critic, whose books include The People and the Books: 18 Classics of Jewish Literature.