Earliest Greek philosophers (those who preceded Socrates ) whose attention to questions about the origin and nature of the physical world has led to their being called cosmologists or naturalists.
Among the most significant were the Milesians Thales , Anaximander , and Anaximenes , Xenophanes of Colophon , Parmenides , Heracleitus of Ephesus, Empedocles , Anaxagoras , Democritus , Zeno of Elea , and Pythagoras .