Addressed to someone who seems to think that the Rishonim are “a movement”:
> there must have been something brewing prior to that time that eventually compelled them... not as individuals but as a movement. After all... isn't that how we think of them... as a movement? Otherwise we
No, why would you think that? We refer to the Dark Ages as a historical period, not as a movement. There wasn't a pan-European revival of obscurantism as a positive value. But philosophical and scientific discovery were repressed by historical factors beyond their own fields of endeavour - overcrowding which made it harder to earn a living, followed by plagues which, by emptying out land, made it easier to acquire land and live off of that, but by the same token, it was hard to till all that land oneself, feudalism didn't lend itself to a society of patronage of the arts and sciences, etc.
> would not refer to them in a group like that. We would refer to them as individuals such as when we refer to the Vilna Gaon vs the Baal Shem Tov and their respective followers.
We do refer to them as individuals. But as a group, they're a historical era, like the Dark Ages or The Renaissance.
(warning, history lecture coming on: )
Do you really not know how we divide halachic eras? We have an overarching principle of "yeridat hadorot" - that the farther we get from the Sinaitic Revelation, the less access we have to authentic Oral Law tradition. Sometimes, throughout history, there are catastrophic events that wipe out most of a generation's intellectual leaders; the next generations, not having had the time to absorb everything from the earlier generations, are then classed as a lesser era. Alternatively, during an era of general hardship, a work may be composed which gains universal acclaim, which too can mark the end of an era.
Within a given era, people are assumed to have roughly the same level of halachic authority. Some individuals may be greater than others, but not sufficiently as to say this individual's word is final within the era.
So the general halachic eras are, as far as I know,
1) Tannaim (from the era of political-intellectual parties during the Hellenistic period until the codification of the Mishnah in 200)
I don't know what historical event might have made 200 a dividing line, I suspect it was simply the universal acceptance of the Mishnah as the starting point for all future rabbinic discussions, giving a structure to legal thought.
2) Amoraim (from the close of the Mishnah to the close of the Gemara, c. 200-500 CE - interesting how that era-closer coincides with the rise of Islam) characterized by textual criticism, intellectual rigor and halachic creativity, story-telling, etc. - the period of creation of most of our fundamental texts, the Gemara, most of the Midrashim, etc. The usual method here seems to be a) establish the correct text of the Mishnah, b) establish that the rule known from Tradition is correct, by comparing it with lots of hypothetical alternatives that make less sense.
3a) Geonim (500-1000), a period of traditionalism, their teshuvot are characterized by laconic answers, without much reasoning. Their legal texts are likewise summaries of the Talmud, e.g. the Halachot Gedolot, c. 800. Many believe that these brief responses reflect the Geonim having the last known traces of authentic Sinaitic traditions, so they could say "this is the answer" without having to prove it from a bunch of alternative ideas.
The next cataclysm, the Crusades, seems to have marked the boundary between the Geonim and Rishonim. E.g. the H"G and the Rif are both summaries of the Talmud, but the Rif inserts more interpretive material, which marks him as the beginning of the Rishonim. [N.B.: there isn't really a difference in halachic authority between Geonim and Rishonim, nor is there an authoritative code that demarcates a boundary. However, there is the historic dislocation and a shift in interpretive style. So the next period should be 3b, not 4. See comments for discussion.]
3b) Rishonim (1000-1550): again a period of creativity and explanation of earlier ideas. Lots of different rishonim had different agendas, e.g. the Tosfos' agenda, according to RRW and his teachers such as Agus and Grinstein at YU, was to promote the Bavli as the primary study text - while the Yerushalmi and oral tradition were more relevant as psak texts for daily life among the Jews of Christendom. So Tosfos (as a movement with an agenda) demonstrated time and again how Ashkenazic practice, while differing from the Bavli's ideal, fulfills the same underlying goals. E.g., covering the challah on Shabbat/Yom Tov reflecting the change in foodways between Greco-Roman Judaea and Franco- German Europe, in Ch. Arvei Pesachim. Or the worldwide change in parchment production of the early Middle Ages, being justified against the Bavli in Megillah. Meanwhile, the Rashba was making stabs at probability theory, in trying to understand and explain the rules of sfek sfeka - when do we add probabilities, when do we multiply them, how does rov quantify as probabilistic, etc. The early 19th C. author of Shev Shmaitsa also gropes in that direction, shortly before Bayes systematized probability theory.
We talk about them collectively, because they collectively explain the Gemara, the main text of Jewish law. They collectively are the major commentators on Tanach and Talmud, so their ideas on understanding the texts have to be our starting point in understanding them.
4) Acharonim (1550-present?) I'd guess the global upheavals affected this transition, but it is mostly marked by the publication of the Beis Yosef and the Shulchan Aruch (with Mapah). If there was a transition era, it might run from the Tur (late 1300s) through the Mapah (1560s). Well, what upheavals? The Black Death of 1348-1350, which killed 1/3 of Europe. The Renaissance of the 1400s-1500s, with new wealth generated by fewer people working the same land of Europe, and the shift from feudalism to patronage. The end of Byzantine Rome and the rise of the Ottomans in 1455. Printing in 1450. Availability of printed Talmuds and printed Rabbinic Bibles starting c. 1521. And, of course, the end of Jewish Spain - the expulsions, the conversos, the Christianos Nuevos, the re-converted back to real Judaism, the exile all over the Mediterranean basin, the Inquisition (what a show).
The Shulchan Aruch (1565,1578), the Zohar (1558), and the teaching of the Ari in the early 1570s all happened within a decade or two. As a marker of a shift in Jewish intellectual history, it's hard to beat that period.
And the Acharonim largely explain the Rishonim, and try to reconcile them to find a final psak, or compare their ideas one to another to decided which is more convincing, or introduce Kabbalah into the
Read the books of R' Zechariah Fendel for discussions of the various eras and major figures in each era.
> The point is... why are we referring to them in such a large grouping? We must recognize that they were doing something different than the previous grouping and different yet again from our current grouping.
Yes, they had a lesser level of connection to Sinai than the Geonim, and a greater one than the Acharonim.
> On a side note: I think our own era is not well defined as yet because how can we be the last (Acharonim)? Is someone suggesting that the Messiah is in the offing? Then when he arrives, if it is not in my lifetime, won't those folks that come after me be the last?
Some have proposed a 5th era, tentatively called the Tachtonim (those underneath), marked by the dislocations and death of 1870-1960 - a unified Germany that led to Nazism, the Shoah itself, the mass migration to America between 1880 and 1924, the expulsions of the Jewish communities in almost all the Muslim countries, the founding and continued existence of the State of Israel, etc. Certainly death and dislocation have caused a rupture in the Tradition. I don't see a singular text yet that is accepted by klal Yisrael - maybe a combined edition of Igros Moshe and Yabia Omer? This postwar era certainly is characterized by indexing and codification, as well as a revival of Kabbalah among the Ashkenazim, who had largely suppressed it after 1820 to undermine the Sabbatean movement.