Scholar quarreled with almost all his contemporaries.
Reprinted from The Jewish Religion: A Companion, published by Oxford University Press.
Jacob Emden was a renowned Talmudist and polemicist (1697-1776). Emden lived for most of his life in Altona, Hamburg, where he occupied no official Rabbinic position, earning his living by printing books, especially his own, including his prayer book (known as the Jacob Emden Siddur), his collection of responsa, his autobiography (very unusual for a Rabbi), and his valuable notes to the Talmud.
Well known in the history of Jewish controversies is that between Emden and the Rabbi of Altona, Jonathan Eybeschitz, whom Emden suspected of being a follower of the false messiah, Shabbetai Zevi. Like his father, Zevi Ashkenazi, known as the Hakham Zevi, Emden fought the crypto-Shabbeteans and their works, finding traces of this heresy in books hitherto considered to be completely religiously respectable.
Though a Kabbalist and believer in the Zohar as sacred literature, Emden, aware that Shabbeteanism based itself on the teachings of the Zohar, sought to prove that Rabbi Simeon ben Yohai is not, as he is reputed to be, the author of the Zohar. His arguments against the antiquity of the book show that he had a keen critical sense and are still widely used in modern Zoharic scholarship.
Emden's opinions were often extremely unconventional. He could not believe that the pious and orthodox Maimonides could have written the Guide of the Perplexed and maintained, contrary to all the evidence, that the real author of this work was an unknown heretic. Emden believed that Christianity has an important role to play in God's plan for mankind and was on friendly relations with a number of Christian scholars, as he was with Moses Mendelssohn the founder of the Haskalah movement.
Emden has been criticized for his undue interest in sexual matters but while it is true that, for instance, he provides, in his prayer book, details of how the marital act is to be carried out, this is in the context of the Friday night section of the prayer book which, for the kabbalists, is the occasion for sexual congress between husband and wife in order to repeat and assist the union on high between the male and female principles in the Godhead.
In his autobiography, Emden is very frank in describing how he was tempted in his youth to have sex with his cousin, a temptation he resisted. He believed that the ban on polygamy by Rabbenu Gershom of Mayyence was a serious mistake in that it followed Christian mores; although, he states, he does not have the power to urge the ban to be repealed. He even advocates a scholar taking a mistress since, he says, the Rabbis hold that "the greater the man, the greater his sexual urge."