Joseph Rosen (Yiddish , Yosef Rosin; 1858–5 March 1936) known as the Rogatchover Gaon (Exalted One of Rogachev) and Tzofnath Paneach (Decipherer of Secrets—the title of his main work), was a rabbi and one of the most prominent talmudic scholars of the early 20th-century. Rosen was known as a gaon (exalted one) because of his photographic memory and ability to connect sources from the Talmud to seemingly unrelated situations. Rosen has been described as the foremost Talmudic genius of his time.
Rosen was born in Rogachov, now Belarus, into a Hasidic family of Chabad Hasidim, and was educated in the local cheder (elementary school). His unusual capabilities were noticed at the age of 13, when he was sent to study in Slutsk along with Chaim Soloveitchik (5 years his senior), under Yosef Dov Soloveitchik (Beis Halevi). He subsequently studied under Yehoshua Leib Diskin (Maharil Diskin) in Shklov. In 1889, he assumed the rabbinate of the Hasidic community in Dvinsk for almost 50 years, where his non-Hasidic counterpart was Meir Simcha of Dvinsk. They served in parallel until the late 1920s, and enjoyed excellent relations.
Among those who received semikha (Rabbinic ordination) from him were Menachem Mendel Schneerson (seventh Lubavitcher Rebbe), Mordecai Savitsky (1911-1991) of Boston, Zvi Olshwang (1873-1959?) of Chicago (brother-in-law of Shimon Shkop) and Avraham Eliyahu Plotkin (1888-1948; author of Birurei Halachot—a copy of the actual semikha is included in that work).
The Rogachover is remembered for his breadth of Torah knowledge and caustic wit. He did not suffer inadequacy lightly. He was similarly reputed to rarely quote any rabbinic authority post-Maimonides, and avoided recent rabbinic works of the Acharonim in favour of the Rishonim (those preceding the late 15th century). His responses to queries of Jewish law are generally enigmatic and cryptic.
Rosen died in Vienna in 1936 following unsuccessful surgery.
Throughout his life, despite not being an official Lubavitcher Hasid, he maintained very close connections to Lubavitcher Hasidim and their Rebbes Sholom Dovber Schneersohn (Rashab) and Yosef Yitzchak Schneersohn (Rayatz). After Rashab's death, he supported the decision to appoint the young Rayatz as the new Rebbe. The Rogatchover is a famous figure in Chabad-Lubavitch folklore. His name often comes up in stories told in yeshivas and during farbrengens (Hasidic gatherings). Stories range from self-sacrifice and dedication to Torah values despite the pressures of the Russian government, to special sensitivity to the Chassidus and Kabbalah (spiritual dimensions of the Torah) to his genius in the revealed Torah. Menachem Mendel Schneerson once quoted the Rogachover, who said that the whole of Judaism to him could be condensed into ten basic ideas, and were he to be smarter, it would be only one idea.
The Rogatchover was a noted Talmudic scholar and published a number of his works on the Talmud and Maimonides. His main work, a commentary on Maimonides, was published during his lifetime, as were five volumes of halakhic (Jewish law) responsa. The remainder of his surviving writings appeared in the United States and Israel many years after his death; all are titled Tzofnath Paneach (Decipherer of Secrets—a title given to the Biblical Joseph by Pharaoh. His manuscripts were smuggled out of Latvia in the form of micro photographs sent via mail to the Safern family in the Bronx at the outbreak of World War II by his successor, Yisrael Alter Safern-Fuchs (1911-1942), who remained in Latvia to complete this task, and his daughter Rachel Citron, who had come to Dvinsk from the Land of Israel to help preserve her father's manuscripts. Both later died in the Holocaust. A portion of these manuscripts was edited and published by Menachem Mendel Kasher. Seven manuscripts were published by Machon Tzofnas Paneah, headed by Mordechai Pinchas Teitz. Machon Hamaor in Jerusalem is now publishing the remaining manuscripts.
The Rogatchover's works include responsa and novellae on Torah and Talmud. They are regarded as difficult and inaccessible, as he employs the philosophical terminology of Maimonides' The Guide for the Perplexed even in non-philosophical analyses. Kasher, therefore, included Mefa'aneach Tzefunoth (Decipherer of Secrets), an explanatory commentary to facilitate understanding of the Rogatchover's influential work.
The Rogatchover authored a number of works on Jewish law, some of which were published in his lifetime.