The most secret umbrella organization over a host of other secret societies designed to maintain control of the otherwise dangerous mass of humanity.
Working similar to Asimov's Foundation, the Illuminati controls and uses oppossing political forces within a country to focus energy that could otherwise result in dangerous conflict into a harmless contest between two Illuminati members playing roles no more real than world-wide wrestling conflicts.
The Illuminati (and their sub organizations) have as their goal the highest goals of providing a world that is safe for peace and virtue. Many members of sub organizations do not even realize that they are being used in larger scale purposes.
The highest order members of the Illuminati are carefully selected from among the leaderships children to ensure that their upbringing has included both the ability and spirit for independent thought and the comittment to service of humanity. Children are not told the nature of the organization until they have proven themselves in adulthood.
The Illuminati are so widespread that members are only able to recogine other members through an intricate network of Christian symbols, religious keywords, secret handshakes, and membership in sub organizations (e.g. Skull & Bones, Bohemian Grove, Block S, 7 Society, Omega, etc.)