Reply to Saliba

Abstract

Professor Saliba takes exception to views expressed in my Review Essay (“Conaguring the Universe: Aporetic, Problem Solving, and Kinematic Modeling as Themes of Arabic Astronomy,” Perspectives on Science 1998, vol. 6, no. 3, pp. 288–330). His criticisms and reservations mainly relate to questions about the character and the value of what I have called the hay’a project in Islamic astronomy, how and when this project was launched, and about contrasts with other projects and approaches in the same discipline, especially concerning the important question of the relations between physics and mathematics as viewed by the practitioners of the discipline. The following brief comments, kindly solicited by the editors of Perspectives on Science, are meant to sharpen some of our more serious differences, and, hopefully, to remove some misunderstandings. First, with regard to the term hay’a, Saliba makes too much of the term itself as an indication of when a new, and speciacally Islamic, project came into existence. Hay’a is a common Arabic word which means shape, agure or form; and, whether or not it originally rendered a Greek term, it could equally apply to the Aristotelian form (we now say “conaguration”) of the universe as a structure of homocentric spheres, and to the Ptolemaic system of eccentric spheres and epicycles. As Saliba knows, the term appears in the title of one manuscript of the Arabic version of Ptolemy’s Planetary Hypotheses, and could be applied to something as simple as the agure (hay’a) of the earth. That the term came to refer to the science of astronomy in general is therefore not surprising: it emphasized a tendency, prevalent among a large number of Islamic astronomers, to view astronomical theory as primarily concerned to represent the heavens in terms of nested solid spheres obeying some physically accepted principles of motion. Thus an early use of the word hay’a does not by itself imply the motivations and