Anaximander (611–545 B. C.?) was an astronomer and geographer; he made an astronomical globe, a sundial, and a geographical map. He was an intimate disciple of Thales and wrote _Concerning Nature_, which is referred to as the first Greek philosophical treatise. Nothing is known of his life. Anaximenes (560–500 B. C.?) was the disciple of Anaximander. One sentence is preserved of his writings.[9] =The Milesian Philosophy.= The Milesians lived upon the seacoast, and the changes of the sea and air must have deeply impressed them. They had an intellectual curiosity to find the cosmic matter which remained identical with itself and at the same time moved. (See p. 22.) They were not, therefore, interested to discover the chemical composition of matter, but to find what matter was most moving and therefore most alive. Thales said that it was water; Anaximenes, air; and Anaximander, the Apeiron, or the Unlimited. Their respective choices were determined by what seemed to possess the most mobility and the greatest inner vitality. Thales thought water possessed this quality. Water is always moving. Thales saw it moving. It therefore has life in itself. Anaximander felt that no object in our perceptual experience would fully explain the ceaseless mobility of nature, and he called it the Unlimited or the Indeterminate――the Apeiron. It is a mixture in which all qualities are lost. The changes in nature are endless, and therefore the single cosmic substance, from which they come, must be endless as well, for “from whatever source things come, in that they have their end.” We learn that this is just the reason for Anaximenes choosing the air for the single underlying cosmic substance. The air is the most changeable thing and is Unlimited.[9] Both Thales and Anaximenes still held to the traditional polytheism of the Greek Epic. Anaximander rises above them in this respect. This conception of the Unlimited, to which his scientific search led him, is regarded by him as Deity. He calls it “the divine” (τὸ θεῖον); although he speaks of it in the neuter gender it is, nevertheless, the first European _philosophical conception of God_. It is the first attempt to conceive of God as purely physical and yet without any mythical dress. In Anaximander the Milesian monism has a religious aspect.