According to the "Epistle of the Right Path", an anonymous post-Mongol Persian-Ismaili treatise, the exoteric ("zahir") form and the esoteric ("batin") form co-exist, in that the exoteric ("zahir") form is the manifestation of the esoteric ("batin") essence. The outer form ("zahir") without the essence ("batin") is like a mirage or an illusion. The epistle points out that the unbroken chain of Imams that have existed since the beginning of time are the exoteric manifestation of the “Command of God” (the first cause of the universe that in turn caused everything else).