Anaximander, a countryman of Thales, was also born at Miletus, about 30 years later; he is said to have been a pupil of the former, and deserves especial mention as the oldest philosophical writer among the Greeks. He did not devote himself to the mathematical studies of Thales, but rather to speculations concerning the generation and origin of the world; as to which his opinions are involved in some obscurity. He appears, however, to have considered that all things were formed of a sort of matter, which he called τὸ ἄπειρον, or The Infinite; which was something everlasting and divine, though not invested with any spiritual or intelligent nature. His own works have not come down to us; but, according to Aristotle, he considered this “Infinite” as consisting of a mixture of simple, unchangeable elements, from which all things were produced by the concurrence of homogeneous particles already existing in it,—a process which he attributed to the constant conflict between heat and cold, and to affinities of the particles: in this he was opposed to the doctrine of Thales, Anaximenes, and Diogenes of Apollonia, who agreed in deriving all things from a single, not changeable, principle.
Anaximander further held that the earth was of a cylindrical form, suspended in the middle of the universe, and surrounded by water, air, and fire, like the coats of an onion; but that the interior stratum of fire was broken up and collected into masses, from which originated the sun, moon, and stars; which he thought were carried round by the three spheres in which they were respectively fixed. He believed that the moon had a light of her own, not a borrowed light; that she was nineteen times as large as the earth, and the sun twenty-eight. He thought that all animals, including man, were originally produced in water, and proceeded gradually to become land animals. According to Diogenes Laertius, he was the inventor of the gnomon, and of geographical maps; at all events, he was the first person who introduced the use of the gnomon into Greece. He died about 547 b.c.
Anaximenes was also a Milesian, and a contemporary of Thales and Anaximander. We do not exactly know when he
