It was not Zeno, the founder of the Stoics, alone, who taught that the Universe evolves, and its primary substance is transformed from the state of fire into that of air, then into that of water, etc. Heraclitus of Ephesus maintained that the one principle that underlies all phenomena in Nature is fire. The intelligence that moves the Universe is fire, and fire is intelligence. And while Anaximenes said the same of air, and Thales of Miletus (600 years b.c.) of water, the Esoteric Doctrine reconciles all these philosophers, by showing that though each was right, the system of none was complete.