Steve Cohen's February 8 Post op-ed ("I want people to realistically understand intermarriage") has generated vivacious debate. It's been years since the problem raised by Cohen's current outlook - should we be worried? Should we prefer in-reach over out-reach? - moved to center stage of Jewish academic and public debate. It is as if a group of bright and skilled astronauts were in a spaceship discussing the pros and cons of their immediate, and quite static, environment without noticing that their spaceship was actually traveling at thousands of kilometers per hour. Similarly, it's as if the debate about American Jewish sociology and demography was taking place in a vacuum. First off, in weighing the cultural resilience versus cultural erosion of the community you cannot altogether ignore whether it is quantitatively growing, stable or declining. In 2001, the National Jewish Population Survey (NJPS) indicated an incipient trend to decline which probably began soon after the previous NJPS of 1990. It is not simply a matter of taking a representative sample of the general American population, filtering out the relatively small pool of Jewish households, and counting through appropriate weighting and inflating procedures. Demographers can certainly say whether a population is growing or declining based on repeated observations of its age composition, its in-marriage and out-marriage trends, and its reported fertility levels. Since 1970, all of these different indicators have shown incredibly consistent patterns: American Jews had fewer and later marriages, comparatively more frequent marriages with non-Jewish partners (who did not convert to Judaism), and relatively small families - a growing share of which included children whom their parents explicitly did not intend to raise in any kind of Jewish framework. CONSEQUENTLY, in the US there currently are about 1.5 million young non-Jewish descendants reflecting the decisions taken by their Jewish and non-Jewish parents not to provide them even a very minimal involvement with a Jewish cultural context of any sort. These parental decisions crucially and quite irreversibly affected the size of the next Jewish population cohorts. The nearly complete estrangement of these youngsters from any Jewish environment generated a process of demographic aging among the Jewish community, leading to a negative balance between Jewish birth and death rates. No surprise, therefore, that the Jewish collective would decline in spite of the conspicuous number of Jewish new immigrants incorporated into American society these past two or three decades. The results of 2001 had been largely predicted back in the 1970s. Interestingly, after these notions were reiterated following the 2001 NJPS, a strong revisionist reaction appeared from different circles. At first sight the disagreement relied on methodology. It was maintained - by, among others, people lacking any training in quantitative methods - that NJPS 2001 was technically inadequate. As an alternative database, it was suggested that a sum of local Jewish population figures drawn from a host of diverse local studies would outnumber the NJPS national count by at least one million. On the other hand, based on a new "meta-analysis" of several small national samples independently drawn, the Jewish population gap would increase to perhaps 1.5-2.5 million. Frankly, I have some serious methodological concerns with the new study released by the Steinhardt Social Research Institute at Brandeis University, which indicates that American Jewry may number as high as 7.4 million. For my money, the independent national surveys such as the UJC-sponsored NJPS still constitute the best, in fact the only - though admittedly very costly - instrument that may allow for a complex and diverse analysis of the profile of American Jewry. IN FACT, NJPS is the sole source that may allow a simultaneous study at the national level of the effects of demographic factors (such as age, marital status and geographical mobility), socioeconomic factors (such as educational attainment and occupational status), and Jewish identification factors (such as religiosity, community activism, or further normative aspects). Moreover, the sum of local surveys does not even allow producing an occupational distribution of Jews at the national level, while the meta-analysis cannot even provide a national age composition specifying the actual Jewish identificational status of each member in a Jewish household - namely the children - let alone interactions between the various quantitative and qualitative aspects. To give up on large-scale, independently conducted national surveys means regressing the status of Jewish social research many years back to the 1960s, before the first NJPS. Unfortunately this seems to be the current preference of the organized American Jewish community, and of several of the professional investigators whose work depends on that establishment. Jewish population is not a commercial good that can be suddenly invented or discovered, or promoted though a successful out-reach campaign. While we are constrained to acknowledge some variations over time in the definition of the core concept - Who is a Jew? for research purposes - Jewish population should be assessed in the light of historical trends that unfold over the whole 20th century, but especially since the end of World War II. Current findings must be coherently related to the more and less recent past, and intervening mechanisms of change must be convincingly spelled out. By reasonably explainable criteria, there are just less than 5.5 million US Jews. While we can argue about the numbers, I think we need to get beyond that and try to understand the broader processes that shape the numbers. I'd challenge those who claim that today American Jewry amounts to some 7.5 million people to explain how many there were one, two, three decades before. Which, I bet, they will have some difficulty explaining. THE MORE troubling omission in the current socio-demographic debate concerns the absence of any reference to general societal patterns in the United States, as the overarching system within which the existence of American Jews unfolds. The omission is particularly intriguing on the side of those analysts whose declared preference is for theory development rather than mere empirical description. What does American society do to its citizens, including its Jewish citizens? Is America - both the ideal and the real America - a place that primarily stimulates the formation of segregated subcultures, or rather a highly dynamic context leading to the creation of a predominant, if ever-changing mainstream? When we are told that in their identifications Jews are perennially journeying, the main question intriguingly avoided in the debate is whether, on balance, they are moving from less Jewish to more Jewish, or the other way around? The empirical evidence - no matter how technically imperfect - clearly provides the answers, even if in normative terms we may dislike those answers. I also wonder about the scant reference in the current debate to the emerging role in mainstream American society of individualism versus community distinctiveness. Were a convincing argument to emerge that US society is moving toward stronger separate sub-identities, the case could be reasonably suggested that the Jewish corporate response is following suit. But the general evidence seems to show that this has not been the case, either historically or in the experience of the most recent generation. One further aspect of the debate is that it totally ignores the fact that there can be - and there is - Jewish life out of America. Therefore, the tendency is to judge the success and resilience of Jewry merely as a sub-category within the American paradigm. What about a broader bond with other Jewish communities? Can a Jewish community that has successfully responded to the unique requests of American socialization and group definition meaningfully communicate with other Jewish communities worldwide, recognize them as cognate, and be recognized by them as sister? The current debate risks being disconnected from an historical perspective, from comparative observation of Jews in the broader context of American societal transformations, and from the meaning and connectedness of Jewish identity globally. Such self-referent debate - much like our astronauts in the spaceship - risks making many orbits around before ever reaching meaningful landing. The writer holds the Shlomo Argov Chair in Israel Diaspora Relations at the Hebrew University of Jerusalem, and is a Senior Fellow at the Jewish People Policy Planning Institute.