Philosophical Works of Lucius Annaeus Seneca, Vol. 1

Hence he proceeds to the preliminary question concerning physical unity, c. II, in which he argues that as every whole, so the world consists of parts, from which he distinguishes in the world what is left in place of matter, insofar as the parts can be distinguished by the eyes in space, ordered by a certain framework and continuous series among themselves; not so the matter of which they consist III. He applies these to the air, about whose cosmological nature he says a few things, and distinguishes the essential part, as they call it, from the quasi-parts, i.e., those which could be absent or perish while the whole remains; IV, and to the earth, which he outlines cosmologically V. Now he approaches more specifically to treat the nature of the air, and derives from its unity—which some unjustly deny—its intension, i.e., the force of cohesion or elasticity, which he illustrates with examples and shows its utility VI, and refutes those he had just touched upon, who divide the air into particles VII, whose intension he inculcates with new proofs VIII, especially by the force which it exerts upon water and upon solid bodies IX. There follow other physical properties or forces of the air, that it is so widely expanded around, penetrates all things with its thinness, and with its agility—in which it is compared with other elements—that it is cold indeed by itself and dark, in which it differs from the aether, but by external causes in its various regions is affected and affects [things] into the contrary through varying temperature X. To these he aptly continues the condition of the air arising thence from a meteorological perspective, and inquires into the causes of this inconstancy, which he seems to himself to find in climates and in the course of the stars, especially the sun and moon XI. Then he begins to dispute about individual meteors, and indeed about lightning and thunder, the most terrible of all meteors and yet the most frequent, concerning which he deduces the discussion from chap. XII to the end of the book in such a way that, having premised a few things about the distinction of lightning and about that part of their nature which is known, he debates the controversial points, narrating the opinions of others, and indeed those of Anaxagoras, and much more widely those of Aristotle, which occupies the next two sections, XIII and XIV. The Stoics follow Aristotle XV, with whom he is not detained for long, and having interjected a few of his own [thoughts] about the distinction of lightning XVI, he conducts a review of the opinions of the Ionian sect XVII-XX, Anaximenes XVII, Anaximander XVIII, Anaxa-