Pherecydes (flourished around 540 BC), traditionally credited to be the teacher of Pythagoras, was according to Theopompus - and Cicero - the first to write in the Greek language about nature and the gods, one of those texts being Heptamychos, on the origin of the world, existing only in fragments. He is likely to have been the first to proclaim the immortality of the soul, if not second to Thales, and the originator of the principle of metempsychosis, the immortal human soul passing from one body to the next - human or animal - after the death of the flesh.   The beginning of the world he saw as the elements fire, air and water springing from Cronus.