
The symbol can be traced back to the ancient Egyptian udjat, also known as the Eye of Ra or the Eye of Horus, which had solar associations. It was a favorite apotropaic amulet in that culture. Many later depictions feature the eye surrounded by a halo of rays of light. It was then adopted as a symbol of the all seeing eye of the monotheistic God and came to be known as the Eye of Providence. At some point, it was overlaid on a triangle, which could suggest a link back to its Egyptian origins, but according to some sources the triangle was said to represent the Christian trinity and thus was widely used in a Christian context over the past few centuries to represent their God's omniscient nature. This is rather ironic considering that if you do a search on "all seeing eye" it brings up many links from conspiracy theorists who claim the symbol, which appears on the Great Seal of the United States, is a Satanic/Pagan/Masonic/Illuminati/Insert-Your-Boogeymen-of-Choice icon and indicates their subversive nature.