I once read an essay by a woman who said she "observes Shabbat." On Saturday mornings on the Upper West Side, she sat on a park bench with her newspaper and "observed" her friends and neighbors going to shul. Her joke came back to me as I read the now infamous essay on modern Orthodoxy by Harvard law professor Noah Feldman and a fascinating debate between Web editor Joey Kurtzman and Jewish Theological Seminary stalwart Jack Wertheimer. Feldman's piece in the New York Times Magazine conveyed his bafflement at being quietly ostracized by his modern Orthodox day school in the Boston area. Apparently, despite his success as a legal scholar, the school's alumni association refuses to acknowledge Feldman because he married a non-Jewish woman. I'll leave it to others to debate the Jewish community's treatment of intermarriage. I was less intrigued by Feldman's relationship with his wife than I was by his relationship with Judaism. "Despite my intimate understanding of the mind-set that requires such careful attention to who is in and who is out," he writes, "I am still somehow taken by surprise each time I am confronted with my old school's inability to treat me like any other graduate. I have tried in my own imperfect way to live up to values that the school taught me, expressing my respect and love for the wisdom of the tradition while trying to reconcile Jewish faith with scholarship and engagement in the public sphere. As a result, I have not felt myself to have rejected my upbringing, even when some others imagine me to have done so by virtue of my marriage." Of course, Feldman's Orthodox teachers and the angry bloggers who responded believe that that is exactly what he did. He didn't live up to the values, they feel, because he didn't live the values. A similar dynamic is at work in an exchange of e-mails between Kurtzman and Wertheimer, posted by Kurtzman at the cheeky Jewcy.com Web magazine. IT'S A generational debate, with Kurtzman representing a young cohort of what he calls "Frankenjews" - many of them products of interfaith homes - who are cobbling together identities from a variety of cultures and influences. Kurtzman rejects the notion of Jewish "peoplehood" as so much ethnocentrism. "I don't regard the Jewish people as my family," Kurtzman writes. "I feel a great affection for Jewish culture, I value the Jewish tradition, and I feel a connection to other Jews. But there's no point in pretending that this is at all comparable to what I feel for my family." Later he elaborates: "A Jewish life ought to be one in which the wisdom and insights of Jewish scripture and Jewish history help us more effectively engage with, and navigate in, the world in which we actually live. It shouldn't serve as an alternative to that world, a sort of soft Amish-ism by which we retreat to the narrow, particularist concerns of one traditional community." Wertheimer, however, is perhaps the greatest living champion of Jewish particularism. He tells Kurtzman that they "differ on how Jews can best survive and thrive as a small minority in America. You seem to favor ever more accommodation to current mores and values. I contend that Judaism can only thrive if it is countercultural, and the culture it must reject is precisely what you find most appealing." WHAT LINKS Feldman and Kurtzman is their desire to claim membership in a Jewish community that does not accept them for the kinds of members they wish to be. They regard their Jewish identities within a web of influences and experiences that make them who they are. And they seem to wish for the group to adjust its boundaries and strategies to embrace them. But in this case, the group feels that certain markers of who's in and who's out - in-marriage, peoplehood - are non-negotiable. They don't recognize Judaism as an "influence" or a collection of "wisdom and insights." Only in its particularism can its values truly be fulfilled, and only as a counterculture can Judaism survive. It's not parochialism versus universalism. It's membership versus philosophy. A membership society certainly teaches philosophy, but in the interest of self-preservation and achieving goals defined by the group. A philosophy might foster group affinities, but its ultimate goal is to combine with experiences and influences to make individuals who or what they are. I came into a serious Jewish life, as an adult, on the side of Judaism-as-philosophy-for-living. Jewish text and ritual was this amazing set of tools and resources for living the examined life, asking the big questions, finding some big answers. It was the foreground identity that put the background into perspective. But now that I have kids, and had a front row seat on maybe 20 years of Jewish educational and organizational change, my own perspective has shifted. I don't think I can transmit the "philosophy" without the membership. I'm making "maximilist" choices for my family (day school, intensely Jewish neighborhood, synagogue-as-center-of-family-life) because I don't trust the ideas of Judaism to survive unless there are Jewish communities that are committed to living them, as opposed to just loving and respecting them. But that's me. Kurtzman agrees with my description of the essential tension between him and Wertheimer. "The schism I was recommending," he told me in an on-line discussion, "was between those who demand the membership society, and those (like me) who demand the conceptual program. I genuinely don't believe the two groups can be reconciled." That "schism," thanks to intermarriage, will be biological as well as philosophical. For a time, the two sides might pass each other on Shabbat mornings. But they'll be going in different directions. The writer is editor in chief of the New Jersey Jewish News.