Posek

In Jewish law, a posek (פוסק, pl. poskim, ) is a legal scholar who determines the application of halakha, the Jewish religious laws derived from the written and Oral Torah, in cases of Jewish law where previous authorities are inconclusive, or in those situations where no clear halakhic precedent exists.

The decision of a posek is known as a psak halakha ("ruling of law"; pl. piskei halakha) or simply a "psak". Piskei halakha are generally recorded in the responsa literature.

Orthodox Judaism
Poskim play an integral role in Orthodox Judaism. Poskim will generally not overrule a specific law unless based on an earlier authority: a posek will generally extend a law to new situations but will not change the Halakhah; see the article on Orthodox Judaism.
 * Generally, each community will regard one of its poskim as its Posek HaDor ("posek of the present generation").
 * Most rely on the rav in their community (in Hasidic communities, sometimes the rebbe) or the leading posek.

Conservative Judaism
Conservative Judaism approaches the idea of posek, and Halakha in general, somewhat differently: poskim here apply a relatively lower weighting to precedent, and will thus frequently re-interpret (or even change) a previous ruling through a formal argument; see Conservative Halakha. Although there are some "poskim" in the Conservative movement - e.g. Rabbis Louis Ginzberg, David Golinkin, Joel Roth, and Elliot Dorff - the rulings of any one individual rabbi are considered less authoritative than a consensus ruling. Thus, the Conservative movement's Rabbinical Assembly maintains a Committee on Jewish Law and Standards, whose decisions are accepted as authoritative within the American Conservative movement. At the same time, every Conservative rabbi has the right as mara d'atra to interpret Jewish law for his own community, regardless of the responsa of the Law Committee.

Progressive Judaism
Both Reform and Reconstructionist Judaism do not regard Halakha as binding.

Although Reform stresses the individual autonomy of its membership, it never completely abandoned the field of responsa literature, if only to counter its rivals' demands. Even Classical Reformers such as Rabbi David Einhorn composed some. Rabbi Solomon Freehof, and his successor Rabbi Walter Jacob, attempted to create a concept of "Progressive Halacha", authoring numerous responsa based on a methodology laying great emphasis on current sensibilities and ethical ideals. Full text collections of Reform responsa are available on the website of the Central Conference of American Rabbis.

The Reconstructionist position is that if Jews had formed cohesive communities again, their rulings would be binding, but presently Judaism is in a "post-Halakhic state". Therefore, their basic policy is to allow tradition "a vote, not a veto" in communal and personal affairs.

List of poskim and major works
In chronological order, by the year of birth, and if needed, secondarily, by year of death and surname.

Pre-20th century

 * Yoel Sirkis (1561–1640), Bach
 * David HaLevi Segal (1586–1667), Turei Zahav
 * Sabbatai ha-Kohen (1621–1662), Shach
 * Avraham Gombiner (1633–1683), Magen Avraham
 * Yechezkel Landau (1713–1793), Noda Bihudah
 * Vilna Gaon (1720–1797), Gra
 * Shneur Zalman of Liadi (1745–1812), Shulchan Aruch HaRav
 * Avraham Danzig (1748–1820), Chayei Adam
 * Moses Sofer (1762–1839), Chasam Sofer
 * Menachem Mendel Schneersohn (1789–1866), Tzemach Tzedek
 * Shlomo Ganzfried (1804–1886), Kitzur Shulchan Aruch
 * Yitzchak Elchanan Spektor (1817–1896)

Orthodox

 * Yechiel Michel Epstein (1829–1907), Aruch HaShulchan
 * Yoseph Chaim of Bagdad (1832–1909), Ben Ish Chai, Rav Pealim
 * Yisrael Meir Kagan (1838–1933), Mishnah Berurah, Chafetz Chaim
 * Moshe Greenwald (1853–1910), Arugath HaBosem
 * Chaim Ozer Grodzinski (1863–1940), Achiezer
 * Abraham Isaac Kook (1865–1935)
 * Eliezer David Greenwald (1867–1928), Keren L'Dovid
 * Yaakov Chaim Sofer (1870–1939), Kaf HaChaim
 * Avraham Duber Kahana Shapiro (1870–1943)
 * Yonasan Steif, (1877–1958)
 * Avraham Yeshayahu Karelitz (1878–1953), Chazon Ish
 * Yechiel Yaakov Weinberg (1878–1966), Seridei Eish
 * Yosef Eliyahu Henkin (1881–1973)
 * Eliezer Silver (1882–1968)
 * Yehezkel Abramsky (1886–1976)
 * Yoel Teitelbaum (1887–1979), Vayoel Moshe, Divrei Yoel
 * Avraham Chaim Naeh (1890–1954) Ketzos HaShulchan, Shiurei Mikveh, Shiurei Torah
 * Zvi Yehuda Kook (1891–1982)
 * Yaakov Kamenetsky (1891–1986)
 * Aharon Kotler (1892–1962)
 * Moshe Feinstein (1895–1986), Igrot Moshe
 * Yitzchok Yaakov Weiss (1902–1989), Minchas Yitzchak
 * Yosef Greenwald (1903–1984), Vayaan Yosef
 * Joseph B. Soloveitchik (1903–1993)
 * Yitzchok Hutner (1906–1980)
 * Chanoch Dov Padwa (1908–2000), Cheishev Ho'Ephod
 * Shlomo Zalman Auerbach (1910–1995), Minchat Shlomo
 * Yosef Shalom Eliashiv (1910–2012)
 * Chaim Pinchas Scheinberg (1910–2012)
 * Pinhas Hirschprung (1912–1998)
 * Shmuel Wosner (1913–2015), Shevet HaLevi
 * Aharon Leib Shteinman (1913–2017)
 * Ephraim Oshry (1914–2003)
 * Avraham Shapira (1914–2007)
 * Eliezer Waldenberg (1917–2006), Tzitz Eliezer
 * Shlomo Goren (1918–1994)
 * Chaim Kreiswirth (1918–2001)
 * Yaakov Yitzhak Neumann (1920–2007), Ogiro Be'Oholcho
 * Ovadia Yosef (1920–2013), Yabbia Omer
 * Baruch Ben Haim (1921–2005)
 * Fishel Hershkowitz (1922–2017), Klausenburger dayan in Williamsburg, Brooklyn, New York
 * Hayim David HaLevi (1924–1998), Chief Rabbi of Tel Aviv, author of the set of halakha Mekor Hayim
 * Menashe Klein (1924–2011), Ungvarer Rav; Mishneh Halachos
 * Gedalia Dov Schwartz(1925–2020), av beit din of Beth Din of America and the Chicago Rabbinical Council
 * Nissim Karelitz (1926–2019)
 * Nahum Rabinovitch, (1928–2020) rosh yeshiva of Yeshivat Birkat Moshe
 * Chaim Kanievsky (1928–2022)
 * Mordechai Eliyahu (1929–2010)
 * Dovid Feinstein (1929–2020)
 * Ephraim Greenblatt (1932–2014), Rivivos Efraim
 * Zalman Nechemia Goldberg (1932–2020), av beit din, rosh yeshiva of Machon Lev, editor-in-chief of the Encyclopedia Talmudit
 * Aharon Lichtenstein (1933–2015), rosh yeshiva of Yeshivat Har Etzion
 * Meir Brandsdorfer (1934–2009), Kaneh Bosem
 * Yechezkel Roth (1936–2021) Karlsburger Rav, author of Emek HaTeshuvah
 * Shimon Eider (1938–2007)
 * Yisroel Belsky (1938–2016)
 * Yehuda Henkin (1945–2020)
 * Haim Drukman (1932–2022)

Conservative and Reform

 * Jacob Zallel Lauterbach (1873–1942)
 * Louis Ginzberg (1873–1953), The Responsa of Professor Louis Ginzberg
 * Solomon Freehof (1892–1990), Reform Jewish Practice and its Rabbinic Background
 * Isaac Klein (1905–1979), A Guide to Jewish Religious Practice
 * Jacob Agus (1911–1986), Dialogue and Tradition

Living poskim

 * Shmuel Kamenetsky (1924- ), rosh yeshiva, Talmudical Yeshiva of Philadelphia
 * Yitzchak Abadi (1933- )
 * Dov Lior (1933- )
 * Avigdor Nebenzahl (1935- )
 * Yaakov Ariel (1937- )
 * Zephaniah Drori (1937- )
 * Zalman Baruch Melamed (1937- )
 * Yisrael Ariel (1939- )
 * Eliyahu Ben Haim (1940- )
 * Ephraim Padwa (1940-) rabbi of Union of Orthodox Hebrew Congregations
 * Hershel Schachter (1941- ), rosh yeshiva at RIETS
 * Shlomo Aviner (1943- )
 * Mordechai Willig (1947- ), rosh yeshiva at RIETS
 * Yitzhak Yosef (1952- ), Chief Sephardic Rabbi of the State of Israel, author of the set Yalkut Yosef
 * Yitzchak Berkovits (1953- ), rosh kollel The Jerusalem Kollel
 * Osher Weiss (1953- ), Minchas Osher
 * Eliezer Melamed (1961- )
 * Simcha Bunim Cohen (1957- ), prolific author and pulpit rabbi in Lakewood, New Jersey
 * Yisroel Dovid Harfenes author of Yisroel Vehazmanim, Mekadesh Yisroel and Nishmas Shabos
 * Pinchas Toledano, hakham of the Spanish and Portuguese Jews of the Netherlands
 * Gavriel Zinner author of the Nitei Gavriel series on halakha