Humans have always used symbols as instruments of knowledge and as means of expression.
Symbols span the ages and are international as well, contributing to humankind's self knowledge.
One of our most persistent and ancient symbols is that of the Cross, which is both the quintessential cosmic symbol and the symbol of universal, archetypal man. It is the symbol of duality and the union of opposites. The caduceus, a Tau Cross with winged staff and two intertwined snakes, is the symbol of modern medicine. The Tau Cross is associated with Abraham, and is believed by some to have been used by the Jews in Egypt to mark their doors at the original Passover. The Indians of the Americas used the Greek-style cross to represent the sun, the morning star and the four directions.