- Configuring the Universe: Aporetic, Problem Solving, and Kinematic Modeling as Themes of Arabic Astronomy*
The undoubted truth is that there exist for the planetary motions true and constant configurations from which no impossibilities or contradictions follow; they are not the same as the configurations asserted by Ptolemy; and Ptolemy neither grasped them nor did his understanding get to imagine what they truly are.Ibn al-Haytham, Aporias Against Ptolemy, p. 64
Among the sciences acquired by the Arabs from the Greeks, astronomy was undoubtedly one of the most important, and, to the historian who is interested in the dynamics of intercultural transmission of scientific knowledge, it provides probably the most instructive test case for studying the processes of the appropriation and naturalization of the Greek legacy in Islamic civilization. As the richest and most advanced of the “mixed” sciences, those characterized by Aristotle as “the more physical of the mathematical disciplines” (the others included optics, harmonics, and mechanics), astronomy successfully combined techniques of systematic observation with precise methods of numerical computation and the advantage [End Page 288] of geometrical representation. In the Almagest, which Islamic scholars quickly recognized as the foremost authority for the study of heavenly phenomena, Ptolemy argued for placing astronomy at the top of the scientific edifice—higher than physics, which concerned itself with changing, hence unstable and unreliable, things, and higher than theology, which aspired to gain sure knowledge of things imperceptible and hence inaccessible. Only the objects of astronomy, the stars and their motions, so claimed Ptolemy, enjoyed both constancy and accessibility, and, therefore, only these objects were eminently qualified as objects of stable, indubitable knowledge ( Ptolemy 1984, pp. 35–37). The significant overlap in subject matter between astronomy and cosmology ensured the continuation of debates between “mathematicians” (i.e., mathematical astronomers) and “natural philosophers”—debates for which the terms had been authoritatively set by Aristotle with an eye to the astronomy of his time, but which were later resumed in the context of new developments, first in late antiquity and subsequently in the Islamic world, and in which practitioners of these disciplines raised wide-ranging questions of epistemology, the requirements of different domains of inquiry and methods of investigation, and, inevitably, the rival claims of authority and territorial rights. Astronomy’s strong connection or, frequently, confusion with astrology (a connection upheld by Ptolemy himself and eagerly promoted by many Islamic astronomers), by dangling the promise of predictive power over a full scale of phenomena ranging from cosmic events to the outcome of a battle or the length of an individual’s life, helped to entice powerful and rich, but rarely secure, rulers to bestow on astronomers and their enterprise a level of financial and generally protective patronage not enjoyed by practitioners of other secular disciplines, perhaps with the exception of leading physicians, some of whom combined skills in both fields. It was also astronomy that found itself able to render tangible services to religious practice, for example by providing precise means of determining the direction of Muslim prayer toward Mecca, as well as determining the appointed times of prayer. The eventual establishment of the office of muwaqqit or timekeeper in the large mosques implied public recognition of at least a role for astronomical knowledge (if not for astronomy as such) in a permanent religious institution. And it was again astronomy, more than any other imported scientific discipline, that Muslim theologians had to grapple with as they endeavored to develop a religious philosophy (called ‘ilm al-kalam, the science of kalam) in opposition to the Aristotelian-Neoplatonic variety (Sabra 1994b). The student of the history of Arabic astronomy is thus faced with an enormously rich field of inquiry offering a large choice of problems that range from the strictly technical or mathematical to questions of cosmology and philosophical interpretation, [End Page 289] and to others concerned with the contexts of society and political power or of religious belief and practice.
A prominent feature of the Almagest, and literally the first to make what proved to be a long-lasting impression on Islamic astronomers, is the emphasis it lays on the need to test past observations by means of...