Regarding the matter of Beis Shammai and Bais Hillel as described in the gemara and R. Sherira Gaon, in the period between the deaths of Shammai and Hillel and Yavneh, which was approximately a period of about 50-60 years, the image of so many differences between the two schools sounds almost exaggerated. After all, they didn't differ in any of the fundamentals of the Torah and halacha, so the fact that they may have had differences in certain details shouldn't be considered such a big deal. Or have I missed something in this regard?
David Goldman
1) I think a key source to understanding this may be the Gemara in Sanhedrin 88b, where Rebbi Yosi said that originally there were not many disputes in Yisrael. The Beis Din of 71 would reside in the Lishkas ha'Gazis in the Beis ha'Mikdash, and there were two other Batei Din of 23 Dayanim each which also resided in the Beis ha'Mikdash area. If anyone had a difficult question he would ask it to the Beis Din in his local city, and if the judges there had no answer, he may have to come to Yerushalayim. If the question was difficult enough, they would eventually reach the Beis Din of 71 who, if necessary, would take a vote and decide the Halachah. The Gemara then states that when the disciples of Shamai and Hillel grew in number and many had not studied sufficiently under their teachers, differences of opinion increased in Yisrael, and "the Law became like two Laws." We learn from this that the transition from the generation of Shamai and Hillel themselves, and the generation of their disciples, was a crucial one, when the Halachah started to become unclear.
2) We can see the difference between Shamai and Hillel, as well as their respective disciples, in the Mishnah in Pirkei Avos 5:17, which tells us that the prime example of a dispute l'Shem Shamayim was that of Shamai and Hillel. The Tiferes Yisrael (#123) writes that the Mishnah says "Shamai and Hillel," and not "Beis Shamai and Beis Hillel," because it may be that some of the disciples did not always intend l'Shem Shamayim.
3) In fact, we find in the Shulchan Aruch (end of Orach Chayim 580:2) that one of the days on which calamities occured to our fathers, and therefore on which some people fast, is the ninth of Adar, when Beis Shamai and Beis Hillel argued. The Eliyah Rabah there writes that 3,000 of the disciples were killed in the violence. This is a surprising, and possibly not such a well-known thing, but we do see that serious problems were starting.
4) However, most of the disciples had a positive attitude. The Gemara in Yevamos 14b tells us that even though there were several disputes between Beis Shamai and Beis Hillel regarding matters of lineage, the two groups still married into each other, and they behaved with love and friendship towards each other.
Chodesh Tov,
Dovid Bloom
I am sorry that I don't understand. How were they becoming like "two laws" in those 50-60 years after the deaths of Shammai and Hillel? In what crucial respect? Surely it couldn't have been the matter of mere minhagim like the fast of Adar. And if it was differences in shita like between the Beis Yosef and Rema, so why is that terrible? What is "two laws" about that?
DG
1) It may be that the change happened in a period of less than 50-60 years. The Gemara in Sanhedrin 88b suggests that up to and including the time of Shamai and Hillel there was a good unity in the Halachah. It was only in the generation of the Talmidim of Hillel and Shamai that discord started.
2) The first time we find a dispute between Beis Shamai and Beis Hillel is in the very first chapter of the Mishnah in Berachos 10b. Beis Shamai says that in the evening one must say Shema when leaning on one's side (since the Torah says, "when you lie down"), and Beis Hillel says one may say it any way one likes. Rebbi Tarfon said that he was on a journey and said Shema at night while leaning, and he bandits came upon him and he was endangered. They said to him that he should not have gone against the words of Beis Hillel and that is why he got into danger on the journey.
3) We see right at the beginning of Shas how serious the rift had become. The great Tana'im of the generation of Rebbi Akiva (Rebbi Tarfon was an older contemporary of Rebbi Akiva) were not allowed to act in accordance with Beis Shamai because the Halachah had been established in accordance with Beis Hillel.
4) The whole of the eighth chapter of Maseches Berachos is about differences between the opinions of Beis Shamai and Beis Hillel concerning Halachos pertinent to a meal. For instance, Beis Shamai says that, on Friday night, one says first the Berachah of Kidush and then "Borei Pri ha'Gafen," and Beis Hillel says that one does the opposite order.
5) There are many other examples of differences between Beis Shamai and Beis Hillel in everyday practice. Practical Halachah had lost its unity and become "like two Laws."
6) I think that the disputes between the Beis Yosef and the Rema are rather different. These two Poskim were summarizing the opinions of the great Rishonim, who lived in a period of about 500 years prior to them, and deciding between their different opinions. The Beis Yosef put a great importance, for instance, on the opinion of the Rif and the Rambam, while the Rema put more weight on the opinions of Tosfos and the Mordechai. The Beis Yosef and the Rema do not say their own opinions so often. This is very different from Beis Shamai and Beis Hillel when the entire Halachah was placed into a turmoil in the space of one generation.
Dovid Bloom