Jon McGinnis

Avicenna's discussion of space is found in his comments on Aristotle's account of place. Aristotle identified four candidates for place: a body's matter, form, the occupied space, or the limits of the containing body, and opted for the last. Neoplatonic commentators argued contra Aristotle that a thing's place is the space it occupied. Space for these Neoplatonists is something possessing dimensions and distinct from any body that occupies it, even if never devoid of body. Avicenna argues that this Neoplatonic notion of space is untenable on the basis of three arguments. In general he maintains that bodies' impenetrability is explained by reference to dimensionality. Consequently, if it is dimensionality that explains impenetrability, and yet as the Neoplatonists hold space inherently possesses dimensions, material bodies could never interpenetrate space and so occupy it and thus bodies could never have a place. The conclusion is patently false. In additions Avicenna argues that the method used to arrive at the possibility of space is illicit, and so Neoplatonist cannot show that space is even possible. Thus, concludes Avicenna, Aristotle's initial account must be correct. The paper outlines the historical context of this debate and then treats Avicenna's arguments against space in detail.

Avicenna’s _Physics_ is the very first volume that he wrote when he began his monumental encyclopedia of science and philosophy, _The_ _Healing_. Avicenna’s reasons for beginning with _Physics_ are numerous: it offers up the principles needed to understand such special natural sciences as psychology; it sets up many of the problems that take center stage in his _Metaphysics_; and it provides concrete examples of many of the abstract analytical tools that he would develop later in _Logic_. While Avicenna’s _Physics _roughly follows the thought of Aristotle’s _Physics_, with its emphasis on natural causes, the nature of motion, and the conditions necessary for motion, the work is hardly derivative. It represents arguably the most brilliant mind of late antiquity grappling with and rethinking the entire tradition of natural philosophy inherited from the Greeks as well as the physical thought of Muslim speculative theologians. As such, _Physics_ is essential reading for anyone interested in understanding Avicenna’s complete philosophical system, the history of science, or the history of ideas.