The descendant of men learned in rabbinic lore, Abba Mari devoted himself to the study of theology and philosophy, and made himself acquainted with the writings of Moses Maimonides and Nachmanides as well as with the Talmud.
[1] In Montpellier, where he lived from 1303 to 1306, he was much distressed by the prevalence of Aristotelian rationalism, which (in his opinion) through the medium of the works of Maimonides, threatened the authority of the Old Testament, obedience to the law, and the belief in miracles and revelation.
He therefore, in a series of letters (afterwards collected under the title Minhat Kenaot, i.e., "Offering of Zealotry") called upon the famous rabbi Solomon ben Aderet of Barcelona to come to the aid of orthodoxy.
Ben Adret, while reluctant to interfere in the affairs of other congregations, was in perfect accord with Abba Mari as to the danger of the new rationalistic systems, and advised him to organize the conservative forces in defense of the Law.
Accordingly, Ben Adret addressed to the congregation of Montpellier a letter, signed by fifteen other rabbis, proposing to issue a decree pronouncing the anathema against all those who should pursue the study of philosophy and science before due maturity in age and in rabbinical knowledge.
On a Sabbath in September, 1304, the letter was to be read before the congregation, when Jacob Machir Don Profiat Tibbon, the renowned astronomical and mathematical writer, entered his protest against such unlawful interference by the Barcelona rabbis, and a schism ensued.
[2] Encouraged, however, by letters signed by the rabbis of Argentière and Lunel, and particularly by the support of Kalonymus ben Todros, the nasi of Narbonne, and of the eminent Talmudist Asheri of Toledo, Ben Adret issued a decree, signed by thirty-three rabbis of Barcelona, excommunicating those who should, within the next fifty years, study physics or metaphysics before their thirtieth year of age (basing his action on the principle laid down by Maimonides, Guide for the Perplexed part one chapter 34), and had the order promulgated in the synagogue on Sabbath, July 26, 1305.
[7] As the three cardinal doctrines of Judaism, Abba Mari accentuates: (1) Recognition of God's existence and of His absolute sovereignty, eternity, unity, and incorporeality, as taught in revelation, especially in the Ten Commandments; (2) the world's creation by Him out of nothing, as evidenced particularly by the Sabbath; (3) special Divine providence, as manifested in the Biblical miracles.
In Sefer haYarchi, Abba Mari refers to the great caution shown by the rabbis of old regarding the teaching of the philosophical mysteries, and recommended by men like the Hai Gaon, Maimonides, and David Kimhi.
[2] Minchat Kenaot is instructive reading for the historian because it throws much light upon the deeper problems which agitated Judaism, the question of the relation of religion to the philosophy of the age, which neither the zeal of the fanatic nor the bold attitude of the liberal-minded could solve in any fixed dogmatic form or by any anathema, as the independent spirit of the congregations refused to accord to the rabbis the power possessed by the Church of dictating to the people what they should believe or respect.