Background
He was born in Altona but acquired his surname from the town where he officiated as a rabbi (1728-1733), although he preferred the Hebrew acronym Yavets (i.e., Ya’akov Ben Tsevi).
He was born in Altona but acquired his surname from the town where he officiated as a rabbi (1728-1733), although he preferred the Hebrew acronym Yavets (i.e., Ya’akov Ben Tsevi).
The communal disputes in which he was involved, and the vicissitudes of his own family life (Emden lost two wives in succession and several children), made him a harsh critic of German Jewish society. The violent campaign launched against his father in Amsterdam (1713-1714), and his own discovery of heretical imposters (1732), turned Emden into an unrelenting opponent of Shabbateanism, the pseudo-messianic movement founded by Shabbetai Tsevi, which he regarded as traditional Judaism’s mortal enemy.
After returning to his native Altona in 1733, Jacob Emden abandoned the rabbinate and engaged in various business schemes with the hope of achieving financial independence. He was disdainful of Jonathan Eybeschutz, rabbi of the Altona-Hamburg-Wandsbeck Triple Community, whose post he may have considered rightfully his.
From 1744, Emden ran a printing press and published dozens of works reflecting his own scholarly interests and outspoken attitudes. Within the framework of his books, he discussed an astonishing range of topics from medicine and sex to geography and Confucianism. Among his publications were over 350 response, commentaries on the Bible, Mishnah, and Talmud; grammatical and ethical treatises; anti-Shabbatean polemics; and an annotated prayer book known as SiddurBeit Ya’akov (1745-1758) which adopted Hakham Tsevi’s unbiased approach to Sephardic tradition.
In 1751, Emden was shown an amulet designed to guard expectant mothers from the evil eye, deciphered the text, and judged it to be the work of a secret Shabbatean. This amulet was one of several prepared by Eybeschutz. Ignoring the dreadful implications, Emden steadfastly maintained his adverse judgment, which was upheld by most of the German rabbinate. Violent scenes took place in synagogue and at the stock exchange; the conflict made headlines in the general press and split Jewish opinion from Holland to Lithuania. Eybeschutz found new supporters outside Germany and remained in office until his death (1764), but Emden continued the battle with a scholarly critique of the Zohar — written to undermine Shabbatean claims — which appeared four years later.
Much valuable information about the social and religious history of his time is contained in Megillat Sefer (1896), Emden’s autobiography. Recent investigation points to the accuracy of Emden’s charge that the venerated Jonathan Eybeschutz was a crypto-Shabbatean. There can be little doubt, however, that the war between these two men (anticipating an even more violent conflict over Hasidism at the end of the 18th century) helped to weaken rabbinic authority of the modern age.