The \textit{Book of hypotheses} of Claudius Ptolemaeus and the Arabic translation of his work (Q2717225)

This article lays bare some very important problems in the Greek tradition of mathematical astronomy, problems that become more vividly obvious especially when perceived through the prism of the relationship of this Greek tradition to the later medieval Arabic astronomical tradition that was inspired by it. By focusing on three major works of the Greek tradition, namely, the Almagest, the Planetary Hypotheses, and Phaseis, which were all penned by Ptolemy (fl. 150 AD) the most sophisticated of the Greek astronomers, the author draws the following important conclusions: NEWLINENEWLINENEWLINE(1) He establishes beyond any doubt that those works of Ptolemy could not be known in their totality without recourse to the Arabic sources, not only because good portions of those texts, if not all in some cases, are no longer extant in Greek, but because the Arabic sources which contained the translations of those texts go back to a much earlier date than the earliest extant Greek texts and thus offer at times variant readings of those texts that antedate the readings of the oldest Greek manuscripts. NEWLINENEWLINENEWLINE(2) He stresses the importance of reading all those texts together as they represent the various developments in Ptolemy's thought in order to avoid the common practice, followed by historians of science until very recently, of reading Ptolemy as the author of the Almagest only, and relegating the other texts to a much lower status. In this regard the author demonstrates with brilliance how this method of reading Ptolemy, not only distorted the Ptolemaic ideas, but could not even begin to understand the whole development of Arabic astronomy which read the totality of the Ptolemaic works and reacted to them accordingly. NEWLINENEWLINENEWLINE(3) When reading the Planetary Hypotheses together with the Almagest, the very purpose of the Almagest, the better known of the two works of Ptolemy, becomes quite clear, and consequently the main problems of both works become obvious, central to which is the inherent problem of the conflict between Ptolemy's mathematical representation of the celestial spheres in the Almagest, and their physical material nature as described in the Planetary Hypotheses. The author also demonstrates that those problems were obvious to astronomers of the Islamic domain, but unfortunately continue to be not equally obvious even to modern historians of mathematical astronomy who make the Ptolemaic works the object of their study. The inevitable major conclusion that is forcefully illustrated in this article is that it is futile to speculate or speak of the contents or the motivation behind the Greek and Arabic traditions without acquainting oneself very intimately with the Arabic sources that contain a much clearer picture of the astronomical developments in both traditions.NEWLINENEWLINEFor the entire collection see [Zbl 0959.00025].