Andreas Lammer

Avicenna (Ibn Sīnā, d. 428/1037) was not only a staunch eternalist and a superb modal metaphysician, he was also an impressive natural philosopher. Loyal to Aristotle, he developed his predecessor's theories and defended those concepts which had become subject of criticism (even ridicule) in late antiquity. The result was a physical theory that followed the demands of the Posterior Analytics and proceeded in tune with the innovations of his own metaphysics. It is hardly surprising, then, that both historical and modern readers of his works attributed to him an argument for the eternity of the world which weaves together modal and temporal notions. Upon closer investigation, however, the so-called “modal proof” appears dubious—in terms of both its alleged Avicennian pedigree and its supposed argumentative strength. This chapter presents and examines Avicenna's argument critically against the background of Avicenna's natural philosophy and, especially, his theory of time.

Experts on Avicenna’s natural philosophy are in agreement that for Avicenna, time exists as the result of a now which flows and which through its flow produces time. Having been a prominent interpretation of Aristotle’s account of time in the _Physics_, the theory of the ‘flowing now’ was known to Avicenna from ancient and late ancient commentaries, and is mentioned in his most detailed discussion of time from his seminal work _The Cure_. It is, however, absent from all his other accounts of time and even within his argumentation in _The Cure_, there are strong, heretofore neglected reasons to believe that Avicenna ultimately did not adopt this idea. This article provides a full investigation of Avicenna’s theory of the now and investigates its position within the larger context of his temporal theory, arguing—against the current consensus—that for Avicenna, time is not produced by the now through its flow.

This study is the first comprehensive analysis of the physical theory of the Islamic philosopher Avicenna (d. 1037). It seeks to understand his contribution against the developments within the preceding Greek and Arabic intellectual milieus, and to appreciate his philosophy as such by emphasising his independence as a critical and systematic thinker. Exploring Avicenna’s method of "teaching and learning," it investigates the implications of his account of the natural body as a three-dimensionally extended composite of matter and form, and examines his views on nature as a principle of motion and his analysis of its relation to soul. Moreover, it demonstrates how Avicenna defends the Aristotelian conception of place against the strident criticism of his predecessors, among other things, by disproving the existence of void and space. Finally, it sheds new light on Avicenna’s account of the essence and the existence of time. For the first time taking into account the entire range of Avicenna’s major writings, this study fills a gap in our understanding both of the history of natural philosophy in general and of the philosophy of Avicenna in particular.

This paper traces the reception of the Aristotelian definition of time from its earliest to its most authoritative interpretations, and describes how their readings pave the way for a sophisticated amalgamation of divergent Aristotelian and Platonic elements in the temporal theory of Avicenna. The focus of attention lies on specific perceptions of the relation between time and motion, more precisely on the contrary descriptions of time as the measure of motion and motion as the measure of time. The latter leads to a conception of time as a universal self-subsisting substance beyond all measure, and the former to an understanding of time as an accident providing all motion with its particular measure. It is the antagonism between these two conceptions, both inherent in the Arabic term miqdār at the heart of Avicenna’s definition of time, which arguably informs the Latin tradition and thereby also shapes the early modern contrast between objective and subjective theories of time.