The Kitáb-i-Íqán, the Book of Certitude, was written in Baghdad in 1861 in answer to questions from Hájí Mírzá Siyyid Muhammad, a maternal uncle of the Báb, and Bahá'í tradition holds it was completed in two days and two nights. It is the faith's principal doctrinal text and the one usually given to enquirers first. Its method is exegetical: it takes the apocalyptic imagery of the Gospels and the Qur'an — the sun darkened, the moon not giving her light, the stars falling, the heavens rolled together, the coming of the Son of Man in clouds — and argues systematically that these are symbolic rather than literal, that the sun and moon signify religious leadership and established doctrine, and that the clouds signify the things that veil people from recognising a new Manifestation. Having established the symbolic reading, it argues that every Manifestation has been rejected by the learned of the preceding dispensation on the ground that the literal signs had not appeared. The argument for progressive revelation depends on this hermeneutic and the book supplies it.