This book belonged to Rabbi Yaakov Ben Zion Mendelsohn, another of Britain’s slightly forgotten rabbis. He was a well-known and respected scholar, Talmudist and pulpit rabbi. His original name was Rabbi Yaakov Ben Zion Morein and he was born in Kreitzburg (Latvian Krustpils), in the Vitebsk district of Russia. He changed his name to Mendelsohn to make it harder for the Russian authorities to track him, and emigrated to England. He may have been briefly in Hull and in 1897 he was appointed Rabbi of a synagogue in Leeds, then in Gateshead in 1905 and then in Glasgow, Scotland.
In Glasgow, Mendelsohn defied business interests to bring down communal costs for Passover Matzos. He rented the production facilities of Consolidated Biscuit, koshered it, and ran Matzah production, causing the prior bakery cartel to lose all business for the year. He was active in Zionist circles – in 1909 the Jewish Chronicle records him speaking at a Zionist meeting in Glasgow, pledging loyalty to the Zionist leaders. Rabbi Mendelsohn is listed in Ohalei Shem, a directory of worldwide Rabbis published in 1912.
He emigrated to the United States in 1915, apparently to avoid his son being conscripted into the British army. He settled in Newark, New Jersey, and by 1921 was styled ‘Chief Rabbi of Newark’, where he was in charge of Shechita (ritual slaughtering) and Kashrus. He was also a director and vice-president of the Association of Chabad Hasidim Nusach Ari of the United States and Canada.
Rabbi Mendelsohn wrote four books which were printed in Leeds, England. The first was Shaarei Tzion, printed in 1903 and the second was Sefer Hatzid, printed in 1904.
I have previously written about the next two of his books:
Midrash Yaavetz, which was printed in Leeds, England in 1911.
Mishnas Yaavetz, printed in Leeds in 1913.
This book itself, Maamar HaAchdut, was written by Rabbi Yosef Yavetz, also known as The Chassid and the Darshan. He was born in Spain and left there during the Expulsion in 1492. He finally settled in Mantua, Italy.
He was absorbed with the meaning of the Spanish Expulsion and why it occurred, and wrote an entire treatise, Ohr HaChaim, in which he provided his interpretation. According to R. Yavetz, the catastrophe resulted from Spanish Jewry’s preoccupation with philosophy and secular knowledge which became their central focus, whereas Torah (Biblical studies) and mitzvot (doing good deeds) were no longer the primary purpose of their lives. He was not opposed to knowledge per se, but rather to the fact that it had supplanted Torah and mitzvot in importance.
R. Yavetz became increasingly interested in Kabbalah and encouraged R. Yehuda Chait, who was expelled from Lisbon and suffered terribly until he reached Mantua, to compose a classic Kabbalistic commentary. According to R. Yavetz, there are only three articles of faith, all derived from the passage “I shall be what I shall be” (Exodus 3:14), Creation of the World, Providence and Divine Unity, and Redemption under which he subsumed the thirteen principles of Maimonides.
Jewish Miscellanies 