After the massacre of 1391 in which he lost all of his fortune, R. Simeon left Majorca for Algiers together with his father and family. Jews from other parts of Spain also emigrated to North Africa, and the arrival of the immigrants had a beneficial effect upon the native Jews there. It caused a revival of knowledge and scholarship, which had been neglected and was in a state of great decline. Spanish rabbis now became religious leaders of African communities. In Algiers the aged R. Isaac bar Sheshet was appointed chief rabbi and was also nominated a supreme judge of the Jews by the king. R. Simeon seems to have joined his bet din. Having lost all his fortune and being unable to earn his livelihood from his medical profession, since the native population resorted to superstitious practices rather than to medical help, he was forced to accept a salaried office of rabbi. As Maimonides had prohibited the acceptance of a salary for a rabbinical office, and since in Algiers only Maimonides' decisions were regarded as authoritative, R. Simeon later found it necessary to justify his action.

The nature of R. Simeon's official activity during the lifetime of R. Isaac b. Sheshet can be seen from the following examples. In 1394 a commission to deal with matrimonial laws was appointed, consisting of R. Bar Sheshet, R. Isaac Bonastruc, a rabbi in Algiers, and R. Simeon, who was asked by the other members to draft the ordinances; his draft was accepted in its entirety. Originally intended for the Spanish immigrants, the ordinances were soon adopted by some of the native Jews as well and were authoritative for African Jewry for centuries. A ban against informers issued about that time was also signed by R. Bar Sheshet, R. Bonastruc, and R. Simeon. From the very fact that R. Simeon signed third, it is obvious that he was not assistant chief rabbi as some scholars believe (at least not at that time).

After R. Isaac bar Sheshet's death (1408) R. Simeon was appointed chief rabbi (he himself says dayyan) with the request that his appointment not be confirmed by the king. (According to the report of the Algerian rabbis in the introduction to Tashbez, R. Simeon's appointment already took place during the older man's lifetime.) During his period of office SR. imeon was very active. While he had to fight some practices not in accordance with Jewish religion current among the native Jews, he had to raise his voice against his own countrymen who criticized the doctrines of terefah and were lax in the observance of some commandments. As judge, R. Simeon was regarded as an undisputed authority, and interesting facts have become known of his legal proceedings. From various communities, questions were sent to him about religious and legal matters. He had to deal with the problem of the Marranos from the religious and legal points of view. Of his pupils only R. Abraham ha-Kohen Sholal is known by name, but he may have been his pupil when he was still in Majorca.

R. Simeon was against adopting stringent practices (humrot) which had no foundation in the Talmud; he said that one should be stringent with oneself, but lenient with others. There were some contradictions in him, however, which can also be found among other Spanish scholars. On the one hand he was meek, but on the other he praised himself for his wisdom. Although he greatly admired Maimonides and followed his philosophical views, he believed in astrology which Maimonides so strongly opposed, and he quoted R. Abraham ibn Ezra in connection with astrology, calling him" he-Hasid".

דף [2,ב]: קינה על גזירות ספרד, פותחת: אללי לי ברוב אבלי. אוצר השירה והפיוט, א, עמ' 237, מס' 5151. עם הסכמת ר' נהוראי אזוביב מהוצאת ליוורנו תקכ"ג.