Zakariyya and others like them, matters about which they are absolutely certain, while others know nothing of them. Likewise, the astronomers possess in the writings of Ptolemy, in the rigorously verified Maʾmūnian observations, and in the works of Thābit ibn Qurra and Abū al-Ḥusayn al-Ṣūfī matters known only to them; outsiders remain unaware of them. In this way both groups speak with unwavering conviction about many doctrines upheld by physicians and mathematicians, the experiments conducted by medical experts, and the observational data compiled by those skilled in calculation, while the rest of people remain ignorant of all that. And among the People of the Scripture, such as the Jews, there are also reports concerning Hilāl, Simābī, and others