Future Tense is a fine pun for the title of a book about, in the words of its subtitle, Jews, Judaism, and Israel in the Twenty-First Century. For the last 200 years or so, thinking about the future has made Jews very tense—rightfully so, you might conclude, looking at the historical record. If you gave a pessimistic answer to what was long known as “the Jewish question” in 1840 (the year of the Damascus Affair), or 1881 (when pogroms swept Poland), or 1933 (when the Nazis took power in Germany), you would have found your despair amply justified. But in this new book, Jonathan Sacks, the Chief Rabbi of Great Britain and a prolific author, argues that what was true in the past is not true of the present.In 2010, Sacks writes, what we need is not anxiety but confidence, not withdrawal from the world but a new embrace of it: “It is my considered view that, in this tense and troubled century, Jews must take a stand, not motivated by fear, not driven by paranoia or a sense of victimhood, but a positive stand on the basis of the values by which our ancestors lived and for which they were prepared to die. … Now is not the time to retreat into a ghetto of the mind.” Future Tense lays out Sacks’s vision of what that “positive stand” might look like, in terms of Jews’ relations with one another—in Israel and around the world—and the wider world, including both secular science and culture and members of other religious faiths.Sacks is ideally positioned to argue for this sort of Jewishness—pious yet uncloistered, self-assured but not separatist, engaged with the world but not emptily “universalist”—because it is just the sort of Jewishness he himself lives. As Chief Rabbi, a position with no equivalent in the United States, he is an official spokesman for British Jewry, who often finds himself sitting on government commissions, leading interfaith dialogues, or offering opinions on the BBC. (There is, in fact, a certain amount of vanity on display in Future Tense—Sacks does not hesitate to let us know about his close personal friendships with figures like Isaiah Berlin and Teddy Kollek.)These experiences have convinced him that Jews are by no means as friendless as they may sometimes believe. Certainly, as an American reading the news from Britain, it often seems that Britons’ interest in Judaism takes the form of demonizing Israel and casting suspicion on its Jewish supporters. But Sacks insists that “Jews cannot fight anti-Semitism alone” and writes that he has found Britons of all faiths—Anglican, Catholic, Hindu, even some Muslims—ready to join the fight against “prejudice and hate.” In fact, he persuasively argues, Jews are in some way destined to lead the fight for liberalism and tolerance in Western societies, because for 2,000 years they have been “the quintessential Other” in Christian and Muslim civilization. “That is Judaism’s great contribution to humanity: to show that one can be other, and still human.”What is crucial to this coalition-building, and to Sacks’s whole vision of Jewish assertiveness, is that he speaks not just as a community leader but as a religious leader. Here Sacks’s particular kind of Modern Orthodoxy turns out to be ideal for his task. Few lay figures in the American Jewish leadership would affirm, as Sacks unhesitatingly does, that God literally did choose the Jewish people to play a unique role in the world, and that the Bible can be read as an actual expression of God’s will. (Possibly, few Reform or Conservative rabbis would say so either.) On the other hand, increasingly few Orthodox rabbis have the willingness or authority to engage with the secular world on Jewish terms. “A rabbinate untrained in the wisdom of the world,” Sacks writes, “will find itself irrelevant to those immersed in the world. A Judaism divorced from society will be a Judaism unable to influence society.”How can a belief in Jewish uniqueness foster the practice of Jewish engagement in the world? To answer that question, Sacks turns from polemic to theology, in his chapter “The Other: Judaism, Christianity and Islam.” Judaism, he writes, teaches that “the God of Israel is the God of all humanity, but the religion of Israel is not the religion of all humanity.” This is why, uniquely among the Abrahamic faiths, Judaism does not demand conversion, or believe that all who are not saved through Judaism are damned. Rather, Sacks sees Judaism as dependent on pluralism: Jews do not want to impose uniformity on the world, only to secure a place in the world for Jews, and all others, to worship the one God in their own way. Indeed, the history of Biblical Israel—a small kingdom crushed between the empires of Egypt and Babylon—leads Sacks to call Judaism an anti-imperialist religion, “a critique of empire and the rule of the strong.”This is an ingenious and very appealing theology—a 21st-century Judaism, no doubt, but one that is convincingly grounded in the Bible and history. That it is an incomplete definition of Judaism becomes clear only later in Future Tense, when Sacks turns from the appeal of pluralism to some of the implications of chosenness. One of Sacks’s favorite techniques—it is the classic technique of homily, adapted from the pulpit to the page—is to seize on a feature of the biblical text and turn it into a metaphor for a much larger lesson. Why, Sacks asks in one such passage, does the Bible call God by two names, which he refers to as Hashem and Elokim?Elokim, he suggests, is what non-Israelites call God—for instance, Pharaoh, or King Abimelech of the Philistines. It is God as the pagans can understand him, “the totality of all powers,” which is why the word is plural. Hashem, on the other hand, is “God’s proper name, the name by which he is called in intimate person-to-person relationship: that is not universal.” That is why only the Israelites are permitted to call God by this name: The covenant with Noah uses Elokim, but the covenant with Abraham uses Hashem.It is obvious that this sort of exegesis would be much less appealing to non-Jews than Sacks’s earlier paeans to pluralism. For it amounts to saying that all other faiths have an impersonal, generic relationship with God, while only Judaism knows him intimately and truly. All sincerely held faiths must, at a certain point, make a similar claim—otherwise there is no reason to urge people to belong to one’s own faith rather than another. That is why ecumenicism always depends on a certain amount of euphemism.But with Jews and Judaism, the question is (as usual) a little more complicated. For Jewishness does not depend only on the practice of Judaism, and it is possible to be a Jew while denying that God chose the Jewish people. (One might say, for instance, that Sacks’s reading of the difference between Hashem and Elokim is simply a parable, while the truth—as generations of biblical critics have established—is that God is called by different names in the so-called J and E texts because those texts were written by different human authors at different times.) Sacks recognizes this, of course: As he puts it, Judaism is both a “community of fate”—a people, with a shared history and destiny—and a “community of faith.”Sacks’s contention is that “without the covenant of faith, there is no covenant of fate. Without religion, there is no global nation.” The problem is that, in Future Tense, he is not trying to convince Jews that they belong to the covenant of faith, or that they should. He is not, in other words, arguing that the claims he makes about Judaism and God are true. Rather, he is suggesting that, if we care about the covenant of fate, we should act as if the faith is true, because that is the only way to preserve what Sacks has influentially called “Jewish Continuity.”In other words, Sacks omits the existential dimension of faith, the one in which each of us must decide for him- or herself whether to believe and why. Nor does he really engage with the fact that the decline of faith among Jews is only one aspect of the centuries-long decline of faith among all Western peoples. There are very powerful reasons why it is difficult to believe in Judaism, or Christianity, or Islam, as a divinely revealed faith—reasons stemming from the secular humanist view of history, nature, and ethics. The dilemma, from the point of view of Jewish continuity, is that if a French Catholic stops being Catholic, he doesn’t stop being French. But if a Jew stops being a Jew, is he still a Jew, and why should he even care? That is where the real problem begins, and it is a deeper and more difficult one than Sacks acknowledges.Adam Kirsch is a poet and literary critic, whose books include The People and the Books: 18 Classics of Jewish Literature.