The casual observer of the current presidential polling data requires little expertise to identify a trend stretching back over the last two presidential elections. The population of the United States has been, and continues to be, split almost 50-50 in their support for a national leader.

At the same time, however, the division of country on a national level stands out in sharp contrast to what is happening locally. In his new book, The Big Sort: Why the Clustering of Like-Minded America Is Tearing Us Apart, author Bill Bishop demonstrates how communities are becoming increasingly homogenous as people sort themselves into demographic cliques. The most striking irony, Mr. Bishop explains, is how the increasing singularity of ideas and values in neighborhoods across the country is resulting in increasing divisiveness throughout the country as a whole.

The statistical evidence is compelling. In 2004, in an election decided nationally by one closely contested state (Ohio) and less than 1% of the electorate, almost half the counties in the country recorded landslide victories locally for either one candidate or the other, nearly double the percentage recorded in 1976.

Here are a few samplings from Mr. Bishop’s introduction:

Freed from want and worry, people were reordering their lives around their values, their tastes, and their beliefs. They were clustering in communities of like-mindedness, and not just geographically. Churches grew more politically homogeneous during this time, and so did civic clubs, volunteer organizations, and, dramatically, political parties. People weren’t simply moving. The whole society was changing…

Marketing analyst J. Walker Smith described the same phenomenon as extreme and widespread “self-invention,” a desire to shape and control our identities and surroundings. Technology, migration, and material abundance all allow people to “wrap themselves into cocoons entirely of their own making,” Smith wrote. People are unwilling to live with trade-offs, he said…

As people seek out the social settings they prefer — as they choose the group that makes them feel the most comfortable — the nation grows more politically segregated — and the benefit that ought to come with having a variety of opinions is lost to the righteousness that is the special entitlement of homogeneous groups. We all live with the results: balkanized communities whose inhabitants find other Americans to be culturally incomprehensible; a growing intolerance for political differences that has made national consensus impossible; and politics so polarized that Congress is stymied and elections are no longer just contests over policies, but bitter choices between ways of life.

Is it ever possible for there to be too much agreement? The mishna teaches that if the entire Sanhedrin votes to convict the defendant in a capital case without a single dissention, the death penalty cannot be given. No matter how overwhelming the evidence, the sages did not trust their own objectivity if none of their members could find even one mitigating factor. Brothers cannot testify together in beis din because they share a common perspective that calls into question their collective objectivity.

The more single-minded a group becomes in its opinions, the more calcified its thinking becomes in its evaluation of unfamiliar ideas, and the more quickly it rejects and condemns opposing viewpoints. Moreover, homogenous groups are more likely to devolve into parodies of themselves, shifting to ever-more extreme positions and allowing arguments that might once have been rational to descend to dogma and character assassination.

This is why candidates lean to the extremes in primary elections, laboring to attract support from the farthest wing of their respective parties, the one that is generally the loudest and most vehement. Then, once they have secured the nomination, the candidates tack back to the center for the general election to try and attract voters from across the political divide. Whichever side eventually claims victory will almost inevitably shift back again to the extremes, fearful of antagonizing the clamoring minority by appearing too moderate.

This is certainly one angle of the mishna in Pirkei Avos that praises machlokes l’sheim shomayim: when debate and dispute are motivated by a genuine desire to achieve true understanding, then such debate endures by producing greater clarity, by yielding new truths, and by bringing together ideological opponents who are devoted to intellectual honesty and ideological integrity.

Such was the nature of Beis Hillel and Beis Shammai, who fought fiercely in the study halls but retained love and respect for one another. One has to wonder, given the increasing factionalism within the Torah world, whether students of the two academies would even speak to one another if they were alive today.

After the death of his main disciple, Reish Lakish, Rabbi Yochanon lamented that he had no one to challenge him any more. By posing 24 problems to every law his rebbe taught him, Reish Lakish stimulated the learning of Torah in a way that benefited both students and teacher. The replacement the sages found, Rav Eliezar ben P’das, brought 24 proofs for everything Rabbi Yochanon said, literally driving him mad.

The ideological differences between the different camps within the Torah world are not (yet) so insurmountable that we have any justification for refusing to bear one another’s company. This does not require compromising one’s principles. Rather, it requires a willingness to concede that the world is a sufficiently complex place to allow the coexistence of different but equally legitimate points-of-view, and to not be afraid that the slightest exposure to alternative outlooks within the mainstream of Torah thought will somehow lead to a swift descent down the slippery slope of apostasy.

When two or three schools in one neighborhood, only marginally different in Torah philosophy and united by their inability to make payroll, are each graduating classes of only five or ten students, when men choose to walk into one shul half-an-hour late on Shabbos morning rather than walking into a shul across the street on time because its parishioners wear a different style of kippot, clearly our commitment to the unity of Klal Yisroel is sadly wanting.

From the earliest days of the twelve tribes, the greatest strength of the Jewish people has been our ability to forge diversity into unity. How ironic, and how tragic, that now we have become united against one another.