Discordianism is a religion and subsequent philosophy based on the veneration or worship of Eris, the Greco-Roman goddess of chaos, or archetypes or ideals associated with her. It was founded circa 1958–1959 after the publication of its holy book, the Principia Discordia, written by two individuals working under the pseudonyms Malaclypse the Younger and Omar Khayyam Ravenhurst. The religion has been likened to Zen, based on similarities with absurdist interpretations of the Rinzai school, as well as Taoist philosophy. Discordianism is centered on the idea that both order and disorder are illusions imposed on the universe by the human nervous system, and that neither of these illusions of apparent order and disorder is any more accurate or objectively true than the other. There is some division as to whether it should be regarded as a parody religion, and if so to what degree. Discordians use subversive humor to spread their philosophy and to prevent their beliefs from becoming dogmatic. It is difficult to estimate the number of Discordians because they are not required to hold Discordianism as their only belief system, and because there is an encouragement to form schisms and cabals.