Generalizing about American "people," which includes ethnic, racial or class lines, is chancy when one throws in and observes the religious factor.
Rabbi A. James Rudin focused on the 1.54 million Jews in greater New York – a population larger than that in many historic mainline Protestant groups nationally, Marty says.
Certain features of any ethnic group are so prominent that the generalizer usually does not have much at risk when generalizing.
Odds are good that a person without a doctorate in anthropology and statistics can take for granted that she is understood and agreed with if, for example, she assumes that not many Amish people are Unitarians or that not many Mennonites or Quakers are pro-war partisans.
When dealing with larger and more visible populations, one expects to find less homogeneity than in small, strict, readily profiled groups.
Those who expect the vast majority of Catholic church-goers to oppose practices of contraception have to be ready to revise their sets of presuppositions if survey data of recent decades is to count.
Recent surveys and polls suggest that, for all the vivid exceptions (for example, among neo-conservatives), Jews remain reliably "liberal" or "progressive" or Democratic voters.
Count on such to draw on a variety of elements in their history. These may include the heritage of the biblical prophets, responses to welfare agencies when their grandparents were poor new immigrants or, some cynics will say, thanks to their having been brainwashed by academic elites, until most are molded as liberals in American mainstreams.
"But, no!" say those who look closely; be careful to notice everyone when generalizing.
Making news these weeks are reports on surveys of Jewish opinion that find large and growing pockets of exceptions to the old generalizations.
Best known is a survey by veteran observer and commentator Rabbi A. James Rudin, who sees Jews who do not "fit in."
He has authored a book on cardinals who transformed Catholic-Jewish relations and now comments on New York area Jews. Religion News Survey and the Washington Post picked up on his findings.
Rudin focused on the 1.54 million Jews in greater New York – a population larger than that in many historic mainline Protestant groups nationally, and calls for revision of opinion.
For instance, the once-declining number of Jews there has been replaced by booming populations, thanks in no small measure to the influx of Russian Jewish immigrants. Most are Orthodox, and they represent almost 40 percent of the Jews in surveys.
These Jews have large families. Their children go to Orthodox day schools. Almost half of the area's Jews aged 18-34 have attended such schools, while only 16 percent in the older 55-69 age group did so.
They are conservative voters who press for public funds to subsidize their parochial schools. They oppose same-sex marriage. Many are poor; more than 11 percent require food stamps.
They do not connect with Conservative Judaism, which is down from 23 to 18 percent in 10 years or in Reform, down from 24 to 20 percent in the decade. Few know of or are part of well-established Jewish welfare agencies.
Rudin calls his findings a "Tale of Two Communities." Will tensions between them lead to a different image of Jews in American public life, or is this a localized phenomenon?
Are they on the way toward being assimilated or will they remain a large sub-community?
Jewish leaders are watching closely, as are poll-takers, politicians and any citizens who pay attention to our complex world.
Some leaders, John S. Ruskay, an officer in the UJA-Federation among them, are optimistic that the two populations will interact and let diversity enrich them. Much is at stake, not just for New York Jews.
Martin E. Marty is the Fairfax M. Cone Distinguished Service Professor Emeritus at the University of Chicago. His column first appeared in Sightings.