The Pythagoreans (followers of Pythagoras) believed that all things, even music and astronomy, were fundamentally mathematical in nature. They expressed their ideas in the form of symbols, which were not based on numbers as we know them today.
The image above (the two overlapping circles) is called the Vesica Piscis. The Pythagoreans saw this as the “gateway between worlds” towards the journey of self discovery.
This is the symbol of “twoness, ” or Dyad. In vain, the Moon chases the sun and can never catch up. Thus is the terrible longing to return to one complete being.