 The writings of the Báb and Baháʼu'lláh are considered as divine revelation, the writings and talks of ʻAbdu'l-Bahá and the writings of Shoghi Effendi as authoritative interpretation, and those of the Universal House of Justice as authoritative legislation and elucidation.Some measure of divine guidance is assumed for all of these texts.Some of Baháʼu'lláh's most important writings include the Kitáb-i-Aqdas, literally the "Most Holy Book", which defines many laws and practices for individuals and society, the Kitáb-i-Íqán, literally the "Book of Certitude", which became the foundation of much of Baháʼí belief, the Gems of Divine Mysteries, which includes further doctrinal foundations, and the Seven Valleys and the Four Valleys which are mystical treatises.