The chapter on Tasyīr in Ibn Abī l-Rijāl’s book al-Bāri, and its Castilian translation

Abstract

Tasyīr or “prorogation”, is an astrological procedure with which the astrologer moves, in an imaginary way, an indicator in order to determine the celestial influences. Tasyīr was one of the astrologer’s fundamental tools for the casting of a horoscope. This paper analyzes the information in the chapter on Tasyīr in Ibn Abī l-Rijāl’s (11^th century) book al-Bāri‘, concerning the methods, the techniques and the resources used. Its study highlights the channels through which science was transmitted and the ways in which the astrologer wrote his work using other sources, and stresses the importance of al-Bāri‘ in introducing new astrological knowledge from the East into the Maghrib and medieval Europe (knowledge that was used until the fifteenth century). The comparison of the chapter with its Castilian translation provides evidence of the procedures used by the translators of Alfonso X.