To fulfil the mitzvah of matzah, one is obliged to eat a piece at least the size of an olive at the Seder table. Most of us would eat much more, but matzah minimalists who want to stick to the smallest amount will probably assume they know what that is.

Some 80 years ago, however, one of the most eminent Orthodox rabbis of the day, the Chazon Ish, argued that the size of an olive the sages were talking about was double what it was customarily considered to be. He wasn’t the first to make the case. The Vilna Gaon had thought likewise, though it made little difference to what families did. But the Chazon Ish’s view began to prevail in more religious circles.

It is one example of the greater meticulousness towards halachic detail that has become a hallmark of Orthodoxy in our own day. How did it happen? That is the topic of one of the most influential essays in the past 30 years, Rupture & Reconstruction. It was written by Haym Soloveitchik, emeritus professor at Yeshiva University and former Hebrew University academic, and son of the Modern Orthodox luminary, Rav Soloveitchik. It has just been republished by the Littman Library with additional responses to some of the critiques of the original work.

In the Yiddish-speaking, Ashkenazi heartlands of East Europe, Jews lived in a self-contained world. They absorbed their Judaism not only from their families, but from their neighbourhood, the synagogue, the street. 

Children went to school to learn the basics such as reading Hebrew. But practice was picked up by habit. Judaism was transmitted predominantly by what Professor Soloveitchik calls a “mimetic society”.

But the mass migration that brought millions to the goldene medina of America and other places in the West transplanted them into a different cultural milieu. For the first immigrants and their children, an ethnic Jewishness remained strong so that even those who gave up religion for socialism, for example, retained a sense of “menschlickeit”.

Gradually, American Jews became Americanised. Even non-Chasidic charedim became embourgeoised, wearing “fashionably elegant” sheitls or dining out in kosher French restaurants and speaking English, rather than Yiddish, as their first language.

But as the once low rates of intermarriage began to rocket among American Jewry from the 1960s, so the more religiously committed began to build spiritual enclaves to protect themselves from the corrosive influence of wider society.

In the process, the home as a source of Jewish authority had become weakened and “mimetic” transmission no longer seen as enough. Instead educational institutions became ever more important in shaping the outlook of the young generation. Religious texts came to play a “new and controlling” role, Soloveitchik says.

In the latter half of the 20th century, the number of Jewish day schools in the USA increased from 30 to 570, the pupil population from a few thousand to 160,000. Yeshivah enrolment grew fifteenfold. Whereas in East Europe, yeshivot had largely been reserved for an academic elite, now they became mass institutions, reinforcing the priority of textual study. Jewish texts remained a reliable source of authenticity, unaffected by the shifting currents of the outside world.

But whereas in the past the religious might have relied on family convention, now they sought the correct way of doing things in Jewish books. On many  issues of Jewish law and practice, they would find “a wide variety of different positions”. So, if “one seeks to do things properly (and these ‘things’ are, after all, God’s will) the only course is to attempt to comply simultaneously with as many positions as possible”, Soloveitchik explains. And hence the move to greater ritual strictness.

By the 1990s “what had been a stringency in religious observance peculiar to the right in 1960 … had become the widespread practice in Modern Orthodox circles.”

A new literature on all matters of Jewish ritual and practice — from blessings to tefillin — sprung up to serve those who wanted to be punctilious in their observance. Yeshivah heads, the masters of rabbinic sources, increasingly became figures of influence for those who looked for guidance from the text.

Soloveitchik observes that those who grew up in the shtetl felt a personal intimacy with God, as humorously portrayed by Sholem Aleichem in Tevye the milkman. But in the modern, technological West, where science increasingly explained natural causes, Jews became “irrevocably separated from the spirituality of their fathers”.

So much so that Soloveitchik thinks it “safe to say that the perception of God as a daily, natural force is no longer present to a significant degree in any sector of modern Jewry”.

Instead, the halachically faithful seek “intimacy with His will”, as expressed in the practice of the mitzvot, “a performative spirituality” in which they strive towards ideals of observance.

As Soloveitchik is clear, he bases his observations on the Ashkenazi experience. In response, the head of London’s S & P Sephardi Community, Rabbi Joseph Dweck, has pointed out that the “mimetic” tradition proved more durable in Sephardi communities, though noting that they have since “overwhelmingly succumbed” to “neo-Ashkenazi” influences.

As an account of the development of what we know as right-wing Orthodoxy, Soloveitchik’s is compact and cogent. And some of his insights perhaps apply beyond observant Orthodoxy. Increasingly, in our own community, we have looked beyond the family to instil a sense of Jewish commitment, not only in the Jewish day schools, whose dramatic increase over the past 30 years has been a feature of British Jewry, but in organisations like youth movements too. 

Rupture & Reconstruction — the Transformation of Modern Orthodoxy is published by the Littman Library of Jewish Civilization £29.95