The Rasā'il al-Ikhwān al-safā' (Treatises of the Brethren of Purity) is an Islamic Encyclopedia consisting of fifty-two treatises on different topics, with an additional comprehensive Treatise (Risālat al-jāmi
(8) The Four Elements (fire, air, water, and earth) come immediately under the sphere of the moon where they are subjected to generation and corruption. The Ikhwān adopt the view of Thales (d. c. B.C.E. 545) and the Ionians that the four "elements" change into one another, water becomes air and fire; fire becomes air, water, earth, etc.
The Ikhwān al-Safā' took over the theory of Democritus of Abdera (d. c. B.C.E. 370) which considered man as a reduced model of the universe (microcosm), and the universe as an enlarged copy of man (macrocosm). They regard the human being as a miniature world. (Netton, pp. 14-15) The individual souls (al-nafs al-juz'iyya), representing the infinite powers of the Universal Soul, began to form. During a very long time, these souls filled the world of spheres and constituted the angels, who animated heavenly bodies. In the early stage, the angels contemplated the Intellect and performed the worship due to God. After a lapse of time, some of these individual souls began to forget much about their origin and office. Their inattention caused the fall of the souls into the physical earth. This explains the metaphysical origin of life on earth.