This chapter concerns the medical background of Aristotle’s accounts of heat, pneuma, and the vegetative soul. Bartoš discusses four Hippocratic texts (namely On Flesh, On Regimen, On Sevens, and On Winds) in which heat/fire plays a prominent role. He illustrates the relation of the notion to soul and pneuma in these texts and suggests several remarkable details of special importance to Aristotle’s zoology.

Aristotle divides the physical world between a celestial realm, which is alive but neither hot nor cold, and a sublunary realm, which is moved by heat in two forms: the vital heat of the biological works and the inanimate fire, the operation of which is explained in the Meteorologica. In the context of the second division we find Aristotle distinguishing between the macrocosm (roughly the world according to Physics, de Caelo, Generation and Corruption and the Meteorologica) and the microcosm (the realm of the biological works, the individual sublunary animals). Wilson argues that this second division does not overturn the first one, but rather complements it, for it has some bearing on the question of solar and vital heat. He further argues that Aristotle mediates the macrocosm and the microcosm through the conceptual apparatus of the spontaneous generation in which heat plays a manifest role.

King explores the reflection in both Plato and Aristotle on styles of causal explanation in the explanation of nature, and examines several texts in which they react to theories of natural necessity in this context. He also reviews the influence of Werner Jaeger’s scholarship on the question of Aristotle’s relation to authors in the Hippocratic Corpus.

Roreitner scrutinizes Aristotle’s physiological description of perceptual processes, for which two alternative interpretations have been advocated in the past: it is either pneuma or blood which secures the communication between the peripheral organs of distal senses and the central organ. Roreitner assesses both these traditional interpretations and provides a third alternative according to which it is the body of blood-vessels rather than their content which provides this communication.

Lennox explores the role of cooling in the regulation of natural heat and the preservation of life with special interest in methodological questions about how Aristotle arrived at his views about the critical role of cooling in the lives of blooded animals and why he insists that both the brain and the lungs are involved in moderating the animal’s heat. Lennox concludes that Aristotle was somewhat perplexed by the brain, and that his changing views about its presence in the cephalopods may be an indication of that perplexity.

Tor argues that Parmenides conceives of the soul as a hot, fiery, aethereal and divine thing, and that this notion plays an important role in his epistemology.