The early Islamic period witnessed the appearance of a new astronomical disci-pline, ʿilm al-hayʾa (science of the configuration’ of the universe), which had no Greek equivalent per se. In an effort to determine the conditions underlying this development, the paper argues that its main impetus was a rejection of the discipline of astrology, which was conceived to be an integral part of the imported Greek astronomical tradition and which was opposed by social forces sufficiently influential to compel the principal intellectuals of the day to dissociate themselves from it. Astrology’s opponents were not only religious figures, but included, among others, physicians and even astronomers who, in the end, created a new discipline that was free of the stigma attached to Greek astronomy. The evidence for these developments comes from the work of a contemporary author named Abū Maʿshar al-Balkhī (AD 787-886), whose famous astrological work, Al-Madkhal ilā ʿilm aḥkām al-nujūm (Introduction to the science of the judgements of the stars), devotes a full chapter to the opponents of astrology, which included most sectors of society, even those considered the discipline’s natural allies. In order to corroborate Abū Maʿshar’s assessment, recourse is made to the well-known, but relatively later Muʿtazilite author, ʿAbd al-Jabbār (d. AD 1025/26), whose famous work, Tathbīt dalāʾil al-nubuwwa (Confirmation of the signs of prophecy), contains a full attack upon astrology and all those associated with the foreign sciences in Islam. The paper concludes by asserting that the identification of astrology with Greek astronomy and its consequent denigration in the newly-emerging Islamic environment left practicing Islamic astronomers with no option but to dissociate themselves from both disciplines and to create a new astronomy that may be called Islamic. In order to distinguish this new astronomy from its Greek antecedents, it was given a new name: ʿilm al-hayʾa.‬