It seems especiallyrelevant to talk about astrologers in a volumededicated to scholarly circles in ʿAbbāsid Baghdādgiven the pivotal role they played in the foundationof the city. Indeed, as noted chiefly by al-Ya ʿqūbī(d. after 292/905), several of them—namely Nawbakhtal-Fārisī (d. ca.160/777), Muḥammad b. Ibrāhīm al-Fazārī (d. between180–90/796–806), Māshā ʾAllāh b. Atharī (or b.Sāriya, d. ca. 200/815–6), and ʿUmar b. al-Farrukhān al-Ṭabarī (d.200/815–6)—were responsible for casting thehoroscope of the new ʿAbbāsid capital, thusselecting an auspicious day to ensure its brilliantdestiny. In doing so, they offered posterity a goodexample of “cathartic” astrology (usually referredto in Arabic as ikhtiyārāt, i.e. “choices” or“elections”), a major branch of classical astrologyused to select the ideal moment to begin a givenproject or activity. The astrologers chose the dateof 30 July 762 (3 Jumādā I 145), as evidenced by thehoroscope preserved by al-Bīrūnī (d. after442/1050). It was for instance “on the basis of thatchart that astrologers had predicted that no caliphwould ever die in the city” and foretold theeminence and splendor of Baghdād. As aptly noted byR. Arnaldez, Baghdād was thus born “under the aegisof the scholars”.

The role of the astrologers responsible for the fortuneof al-Manṣūr's new capital invites us to evaluatemore broadly their place and function in the earlyʿAbbāsid period. I will then analyze morespecifically their largely ignored contribution tohistorical writing during the first centuries ofIslam, with the flowering and subsequent decline ofthe specific genre that constitutes astrologicalhistories.

Astrology in the Early ʿAbbāsid Period First of all asimple remark: as pointed out by G. Saliba, “in theArabic sources dealing with the classification ofscience”, like Ibn al-Nadīm's Fihrist (wr. 377/987–988), “confusionbetween astronomy and astrology is often thenorm”.