 The supposed connection between the Epistle of the Brethren of Purity and the Ismailism should have suggested the adoption of this work as one of the main sources of the so-called “Jewish Ismailism” as found in Late Medieval Yemenite Judaism. This “Jewish Ismailism” consisted in adapting to Judaism some Ismaili doctrines about cosmology, prophecy, and hermeneutics (Kiener 1984). There are a number of cases showing that the Brethren of Purity influenced some Yemenite Jewish philosophers and authors in the period 1150–1550 (Langermann 1996). For example, chapter two of the Judaeo-Arabic theologic-philosophical work by Natanael Ibn al-Fayyumi, the Garden of Intellects (Bustan al-‘uqul), written in Yemen in 1165, includes a correspondence between numbers 1–10 and ten scientific and philosophical concepts (soul’s faculties, senses, directions, bodily substances and parts, etc.) most of which are identical to those listed by the Brethren of Purity. Some traces of the Brethren’s doctrine of the procession of beings from the First Intellect, as well as of their numerology, are found in two Yemenite philosophical midrashim, i.e. Judaeo-Arabic interpretations of Biblical texts, written in 1420–1430: the Glad Learning (Midrash ha-hefez) by Zerahyah ha-Rofé (Yahya al-Tabib) and the Lamp of Intellects (Siraj al-‘uqul) by Hoter ben Solomon (Mansur ibn Sulayman al-Dhamari) (see Blumenthal 2007).