The certitude of astrology: The scientific methodology of Al-Qabīsī and Abū Ma'shar.

Abū Ma'shar (787-886) and al-Qābīsī (mid-10th century) were active astrologers and defenders of the scientific character of their discipline. They wrote works on criticisms brought forward against the discipline and challenged practitioners whom they considered as detrimental for the esteem and future fate of their science. Nevertheless, both writers can be seen as heirs to a single tradition of thought, which took its origins in Ptolemy's Tetrabiblios and developed largely independently of the religious philosophical beliefs of a specific community. The arguments developed for proving the scientific value of astrology are interesting in their own right, and merit further study not only by historians of science but also by historians of philosophy.