The tetrad (the elements) plus the monad equals the pentad. The Pythagoreans taught that the elements of earth, fire, air, and water were permeated by a substance called ether--the basis of vitality and life. Therefore, they chose the five-pointed star, or pentagram, as the symbol of vitality, health, and interpenetration.

And Athamas the Pythagorean having said, "Thus was produced the beginning of the universe; and there are four roots - fire, water, air, earth: for fro...