Aristotle's Concept of Fire

The dissertation focuses on the various conceptions of fire found within Aristotle’s physical corpus. It consists of three chapters, each one devoted to one particular aspect of Aristotle’s theory. The first chapter inquires into fire as an element, in particular within the De caelo and the De generatione et corruptione, where Aristotle’s general view on the elements is outlined. Here the emphasis is placed on the different relation between fire and the other elements within the two works. In the DC fire possesses an ontological primacy over the other sublunary elements because of its more formal nature, due to its lightness, its upward motion and its natural place, which is at the extremity of the sublunary region. On the other hand, in the GC it is put on the same level as the others, at least with respect to their mutual generation and corruption. The second chapter is devoted to fire within Meteorologica I-III, where sublunary phenomena of inorganic nature are dealt with. Here we find three different conceptions of fire: (a) as an element, (b) as a hot, dry exhalation, (c) as a process of combustion. I argue that those conceptions do not overlap, but rather peacefully coexist in the same framework. In fact, in the observable cosmos (a) elemental fire (as well as the other three sublunary elements) is found only potentially, i.e., within compound bodies, (b) the dry exhalation, which is a compound body, is the phenomenal version of elemental fire, and (c) flame, and combustion in general, is a process, not a body. The third chapter deals with fire within Aristotle’s biological works, i.e., the Parva naturalia and the zoological treatises. It analyses and discusses the relation between fire and vital heat, especially with respect to those physiological processes based on fire 'analogies' such as pepsis (also treated in Meteor. IV) and the kindling, growth and extinction of the vital heat of living beings. As in the DC, here fire’s most important feature is its formal nature, which this time is mainly connected to its heat.