Encyclopædia Britannica, Ninth Edition/Anaximenes of Miletus
Anaximenes of Miletus may have been a younger contemporary of Anaximander, whose pupil or friend the ordinary tradition represents him to have been. To him it seemed that the air, with all its variety of contents, its universal presence, and all the vagueness which it has for the popular fancy as the apparent source of life and growth, was what maintained the universe, even as breath, which is our life and soul, sustains us. This vital air, boundless in its kind, is the source of the world's life. Everything is air at a different degree of density. Eternal movement pervades it; and under the influence of heat, which expands, and of cold, which contracts its volume, it gives rise to the several phases of existence. The process is a gradual one, and takes place in two directions, as heat or cold predominates. In this way was formed a broad disk of earth, which floats like a leaf on the circumambient air. Similar condensations produced the sun and stars; and the flaming state of these bodies is due solely to the extreme velocity of their motions. (See Ritter et Preller, Historia Phil. §§ 23–27; Mullach, Fragmenta Phil. Græc. i. 241–243.)W. W.