 Epistle 7 On the theoretical arts carefully sketches the Ikhwân's epistemological vision. A sort of “table” of human sciences is given (I, 266, 14–274, 21). There are three kinds of sciences in hierarchical progression: the “propaedeutical” (or preparatory, al-riyâdiyya again; “a designation not absolutely unambiguous” according to de Callataÿ in El-Bizri; de Callataÿ 2017, 78 ff.), those imposed by religious Law (al-shar‘iyya al-wad‘iyya) and the “philosophical sciences allowing the full comprehension of truth” (al-falsafiyya al-haqîqiyya, higher than the religious sciences). The sciences listed first in the table are labelled “propaedeutical” just as the “trivium” and “quadrivium” sciences of the encyclopedia, but here the term is used in a totally different sense. It concerns matters of practical utility, such as reading and writing, grammar and poetry (someway close to the “trivium” sciences), but also magic, mechanics, arts, trades, history and so on. Although the Ikhwân state that the sciences of the third group – the “philosophical” in the higher sense of the word – are the object of their Epistles, they do not coincide exactly with the contents of the encyclopedia, at least, with those of the corpus now available. So, the table can be considered as evidence of the fact that the whole encyclopedia has been produced during a very long period of time. On the one hand, it might have been retained as a first draft of the future enterprise; on the other, it shows the further elaborations of the corpus over the centuries.