Two seemingly disconnected news items this week illustrate the contrasting realities defining American Jewry and Israeli Jewry.In New York, rabbis from the post-denominational congregation B’nai Jeshrun announced they would perform intermarriages. Reaction seems quite muted. Meanwhile, in Jerusalem, Prof. Asa Kasher’s proposed Academic Code of Ethics discouraging professors from politicizing the classroom triggered a firestorm.While each story has its own back-story, the juxtaposition is powerful.Lifting the intermarriage ban elicited yawns because it is the latest of so many examples of non-Orthodox American Jewry’s if-it-feels-good-do-it approach to Judaism, reflecting the American tropism toward less clarity, less commitment, less meaning.Imposing academic limits governmentally is yet another example of Israel’s command-and-control approach, reflecting the Israeli tropism toward a heavier hand rather than a lighter touch, which risks suffocating, not liberating. Judaism, at its best, like a light, fluffy omelet avoids either extreme: it must be more substantive, more satisfying, than the American variety – but, if beaten too hard it turns rubbery and is no longer tasty.Assessed historically, both an intermarriage ban and government-imposed academic restrictions result from modern Jewry’s two greatest achievements. After three millennia of hatred, Jews are loved and free in America – and in most countries where we live. And after two millennia of homelessness, Jews are sovereign and free in Israel.As the cliché goes, Jews are being loved to death: we would not have so much intermarriage if we weren’t so accepted. Faced with this epidemic among the non-Orthodox, many rabbis are “solving” the problem by declaring it an “opportunity.” It’s awkward, because the intermarriage issue involves the most intimate decision people make. Moreover, so many of us know – and genuinely love – the non-Jewish partners in intermarriages that condemning the phenomenon feels like rejecting them. It gets very personal, very quickly.Yet you cannot build something lasting on a foundation of mercury.Having nothing solid at its core makes everything about American Judaism fluid, sloppy, idiosyncratic, excessively personal – and ultimately doomed. If it’s not definable it’s not sustainable. How do you pass on a mushy, feel-good feeling? That’s not how we survived until now.To preserve the Jewish future, we cannot stop condemning intermarriage as a phenomenon; to preserve many current Jewish relationships, we continue befriending non-Jews who love – and marry – Jews.The way out of the conundrum is to learn from the Orthodox and from secular Israelis, who win the battle against intermarriage by not fighting it. Intermarriage can only be fought pre-emptively, decades earlier.In today’s modern world emphasizing pluralism, choice and autonomy, once you are in the defensive position that many American Jews find themselves in, of guilt-tripping or condemning a couple in love, the battle is lost. Only by raising children in rich, meaningful, three-dimensional Jewish environments, where they grow up understanding Judaism as something long-lasting and historical, something broad and communal, and something deep and meaningful, can we make their Jewish identities so precious and comprehensive that they could no more give that up than change their genders.When that Jewish experience really works, it enters an eternal fourth dimension. Being properly rooted, centered and steeped in meaningful Jewish experiences inevitably adds to the identity what Einstein noted in space: the cosmic element of time and timeliness. Judaism resonates because it is not just a construct located in the moment. Rather, as a 3,500-year-old heirloom building toward the future, it has an eternal, timeless dimension as well. That added dimensionality makes it cosmic, extra powerful, even if you don’t believe in God.Judaism’s 4-D identity is relevant to the academic debate too. Prof. Kasher is one of Israel’s leading ethicists, hailed as the architect of the IDF’s ethics code. Kasher has drawn up a thoughtful, subtle code of academic ethics every professor should follow. We shouldn’t impose our politics on our students. We fail them when we propagandize rather than educating.And any Israeli academics with any self-respect, with any consistency, should resign after supporting a boycott of Israel, which means boycotting themselves. Taking a stand rhetorically then violating it essentially is the mark of a fool, not just a hypocrite.But here’s the rub. As much as I want my colleagues endorsing Prof. Kasher’s code, I want them internalizing it voluntarily. The great opportunity Israel offers of sovereignty, of state power, requires Jews, after millennia of homelessness, to learn how to use power – and learn when not to use it. Self-imposed academic restrictions are principled; state-imposed ones are oppressive. The problem is not with Kasher’s code – it’s with any kind of government restrictions which would inevitably lead to nightmares forcing compliance, including financial blackmail, McCarthyite review boards, student informers and other professional penalties.Freedom in Israel and elsewhere, like Jewish identity everywhere, needs that timeless, ineffable fourth dimension.State laws belong to the more prosaic part of life, the warp and woof of the mundane we all need to function properly. Phenomena like Jewish identity, like the academic mission, have their practical sides, but only really work when their more cosmic sides, their fourth dimension, are nurtured and respected. In a modern Jewish world blessed with so much freedom, and the old-new renewal of Jewish sovereignty, we need to learn how to indulge our freedoms within limits – and how, by embracing limits and frameworks voluntarily, we can find deeper meaning in that eternal fourth dimension.Gil Troy is the author of The Age of Clinton: America in the 1990s. His forthcoming book, The Zionist Ideas, which updates Arthur Hertzberg’s classic work, will be published by The Jewish Publication Society in Spring 2018. He is a Distinguished Scholar of North American History at McGill University. Follow on Twitter @GilTroy.