1) Rabeinu Yakov Yisrael is mentioned in other places by Tosfos. Tosfos in Yoma (end of 46b) writes again that Rabeinu Tam sent a response to "the Rav Rabeinu Yakov Yisrael." Tosfos in Chulin (113a, DH Hani) cites "HaR'R Yakov Yisrael," this time not asking a question, but giving a ruling. He permitted a whole tub full of meat which had been salted thorougly together with a carcass. The Rosh there (#33) cites him as "Rabeinu Yisrael" but an emendation there (starred) writes that it should read "Yakov Yisrael."

2) It seems that he wrote a Sefer, because the Mordechai in Shabbos (#273) writes that "H'R Yakov Yisrael wrote that just like the Chanukah candle should be lit in the correct place (and not lit in the wrong place and then moved the right place), so too the Shabbos candles should be lit in the correct place from the start." We also find in the Shiltei Giborim on the Mordechai in Shabbos (on page 146 of the standard editions, referring to the Mordechai #330, on the letter Heh in the Mordecai, but it is quite a long way after the start of the piece in the Shiltei Giborim) that Rabeinu Tam responded to "the Chaver R' Yakov Yisrael." The word "Chaver" is often used in Chazal to signify a Talmid Chacham. Rabeinu Tam said to him that "if your heart is directed towards Heaven (if you have an altruistic intent), you will find that my words are correct." Rabeinu Tam said to him that "I am not amazed if you did not learn the words accurately, but I am amazed that you erred in the understanding of the words of the BH'G (the Ba'al Halachos Gedolos)."

Rabeinu Yaakov Yisrael must have been very close to Rabeinu Tam.

3) Since we have seen that Rabeinu Yakov Yisrael was close to Rabeinu Tam, it is worthwhile to look at Rabeinu Tam's Sefer, Sefer ha'Yashar, to see how he is mentioned there.

a) First, I must correct what I wrote above, in point 2, in the name of the Shiltei Giborim on the Mordechai in Shabbos. The Teshuvah that is cited there is in fact to be found in the edition of the Sefer ha'Yashar that was published by Rav Rosental in 5658 in Berlin. It is in Siman 48, and it is an answer to questions posed to Rabeinu Tam by Rabeinu Meshulam in Siman 47. The critical comments that I cited above were in fact addressed to Rabeinu Meshulam, not to Rabeinu Yakov Yisrael. In the middle of his reply to Rabeinu Meshulam, Rabeinu Tam writes, "I have previously explained the topic of 'a fountain makes things pure even with a minimal amount of water' (see Mikva'os 1:7) to the Chaver Rabeinu Yakov Yisrael."

b) We see that Rabeinu Tam refers to Rabeinu Yakov Yisrael with great respect as "Chaver." In fact, I saw in a contemporary Sefer (Gedolei ha'Doros, by Rav Yechiel Michal Stern shlit"a, vol. 1, page 6, in the entry on Rabeinu Yakov Yisrael) that he refers to him as one of the scholars of France, and writes that he was a Talmid of Rabeinu Meir (the father of the two brothers Rashbam and Rabenu Tam) and was a Talmid Chaver of Rabeinu Tam. So he was somewhere between being considered a Talmid of Rabeinu Tam and being considered a colleague.

c) Then, in Siman 53 of the same Sefer, we find a question that Rabeinu Yakov Yisrael asked Rabeinu Tam. He writes that he is "the least of my master's servants" (cf. Yeshayahu 36:9) but continues, "My father, see, yes see (cf. Shmuel I 24:12) and open your doors to a youngster like me." This is how Rabeinu Yakov Yisrael implored Rabeinu Tam to answer his questions in Halachah, and the result is that we now possess two places in Tosfos in Shas (Kesuvos 98b and Yoma 46b) where Rabeinu Tam answered Rabeinu Yakov Yisrael.

4) We find that his original name was Yakov, and Yisrael was added later.

a) Let us see, bs'd, how Rabeinu Tam answered Rabeinu Yakov Yisrael in Siman 54.

He opens by complimenting him on "the beauty of your wisdom" (cf. Yechezkel 28:7), "for you walked among holy stones, the students of Meir." This is support for what I cited above, that Rabeinu Yakov Yisrael was a Talmid of Rabeinu Meir, the son-in-law of Rashi and father of Rabeinu Tam.

b) Rabeinu Tam continues and writes, "The mouth of Hash-m will mention him with a new name; your name will be Yisrael, and my name is like your name." This seems to mean that the name Yisrael was added later on, while originally Rabeinu Tam and Rabeinu Yakov Yisrael were both called only Yakov.

c) This passage in Sefer ha'Yashar, which was published only at the end of the 19th century and was not seen by many of the Acharonim, can answer a riddle that has puzzled many. The problem starts in the Teshuvos Chasam Sofer (Even ha'Ezer 2:18, DH v'Al) who writes that in former times it was not customary to call people by two names together; this is a new practice. We do not even find that Yakov Avinu was called Yakov Yisrael together. The Chasam Sofer writes that we never found in Tanach, Shas, or Poskim that anyone is called by two names together.

The problem is that Rabeinu Yakov Yisrael, mentioned by Tosfos in a few places, seems to contradict the rule of the Chasam Sofer! But now that we have seen the Sefer ha'Yashar, we see that his original name was Yakov, and afterwards Yisrael was added for some reason. The Chasam Sofer means that we never find one of the Poskim who was named with two names at birth.

5) Does "Yakov Yisrael" count as one name?

a) The Klausenberger Rebbe zt"l wrote at length (in Teshuvos Divrei Yatziv, vol. 5, Even ha'Ezer 100:3 and onwards) in defense of the Chasam Sofer that one does not find double names in the times of the Rishonim. He suggests (in EH 100;5) that it is only two separate names that they did not use in the time of the Rishonim, while Yakov and Yisrael are not separate names. He writes that Yisrael is an addition to the name Yakov.

b) He writes that we find the name Yisrael only used with Yakov, and no one is called Yisrael alone. I do not understand what he means by this, because there are Rishonim named Yisrael -- for example, Rabeinu Yisrael, the author of Terumas ha'Deshen; Rabeinu Yisrael Alnaqua, who wrote one of the Sefarim by the name of Menoras ha'Ma'or and who was a Talmid of the Rosh; and Rabeinu Yisrael of Brona. However, I think we can use the idea that he mentions that Yisrael is merely an addition to Yakov, so Yakov Yisrael is really one name. The name Yisrael is a higher Madreiga of Yakov, as we find with Yakov Avinu, that being named Yisrael indicates a higher level.

c) I had an idea, based on my own find, bs'd. The Beis Yosef (on the Tur, Choshen Mishpat 369, near the end of the Siman in Mechudashim #4) cites what Rabeinu Yisrael Yakov wrote in a Teshuvah. He commented on the Mordechai, Bava Kama #154. If so, this cannot be the same Rabeinu Yakov Yisrael that we saw in my very first reply, who is cited by the Mordechai, Shabbos #273. The latter Rabeinu Yakov Yisrael lived before the Mordechai and the first one lived after the Mordechai, so it cannot be the same person.

d) I contend that my find is actually a support for the Chasam Sofer, who wrote that we never find double names in the times of the Rishonim. Many challenge the Chasam Sofer's assertion from the name of Rabeinu Yakov Yisrael. However, now that we find a different Rabeinu Yakov Yisrael among the Rishonim -- and we never find any other double name in the Rishonim -- this proves that Yakov Yisrael are not two names but really one name. They are not separate names, because Yisrael is an addition to Yakov.

6) Let's continue the search for double names in the times of the Rishonim:

a) The Teshuvos Mishneh Halachos (5:215, by Rav Menasheh Klein zt"l) also writes at length on this topic and finds quite a few double names among the Rishonim. This is clearly a broad issue, and at the present moment I am only going to relate to one of the names that the Mishneh Halachos found. This is on page 352 (DH uv'Shut). He cites the Or Zaru'a (Bava Kama #27) who quotes Rabeinu Yitzchak bar Mordechai Asher ztlh"h. We see that the double name "Mordechai Asher" existed in the times of the Rishonim (the Or Zaru'a lived in Vienna around 1200-1270 ).

b) However, I found in Tosfos Talmidei Rabeinu Tam v'Rabeinu Eliezer, on the same sugya in Bava Kama (8a, page 30, note 1), that the edtior (Rav Moshe Yehuda Blau) cites the Or Zaru'a but writes that "Mordechai Asher" is a scribe's mistake in the Or Zaru'a. Instead, it should read "Rabeinu Yitzchak bar Rav Mordechai in the name of Rabeinu Yitzchak bar Rav Asher." If so, we have no double name here.

c) I found support for this emendation in the Or Zaru'a, Hilchos Treifos #429. He cites "Rabeinu Yitzchak bar Rav Mordechai who received from Rabeinu Yitzchak bar Rav Asher...." So this is the same pair of Chachamim that Rav Blau cited.

We find also in the Or Zaru'a (Bava Kama #297), "This is what Rabeinu Yitzchak bar Mordechai zt'l wrote in the Tosfos that he made in front of Rabeinu Yav'a zt'l." These are the two famous Ba'alei Tosfos, the Rivam (Rabeinu Yitzchak bar Mordechai) and the Riva (Rabeinu Yitzchak bar Asher). The Rivam was a pupil of the Riva. So if Rav Blau is correct in saying that it is a scribe's error in the Or Zaru'a (Bava Kama #27), and it should not read "Rabeinu Yitzchak bar Mordechai Asher" but rather "Rabeinu Yitzchak bar Mordechai in the name of Rabeinu Yitzchak bar Asher," then the reference is to the well-known pair of teacher and pupil and we have no source for the double name "Mordechai Asher."

d) This is a big topic and I assume that we have only touched the tip of the iceberg.

Dovid Bloom