There are multiple signs and symbols that are used to represent the Illuminati, including the "All-Seeing Eye" (isolated or on the top of a pyramid), the number 666 and the reversed pentagram. The Illuminati also employ hand signals, such as the devil's horns and the pyramid sign.
The Order of the Illuminati was founded in 1776 by Adam Weishaupt, who was a professor of canon law at the time. Advocates of free thought, secularism and liberalism comprised its ranks, where they were sworn to secrecy and had to pledge obedience to their supporters. One of the most familiar symbols that the order uses is the Eye of Providence, which also appears on the dollar bill.