on earth". An introduction to the spiritual universe unveiled in the Kitáb-i-Aqdas would fail in its purpose if it did not acquaint the reader with the interpretive and legislative institutions that Bahá’u’lláh has indissolubly linked with the system of law thus revealed. At the foundation of this guidance lies the unique role which Bahá’u’lláh’s Writings—indeed the text of the Kitáb-i-Aqdas itself—confer on His eldest son, ‘Abdu’l-Bahá. This unique figure is at once the Exemplar of the pattern of life taught by His Father, the divinely inspired authoritative Interpreter of His Teachings and the Centre and Pivot of the Covenant which the Author of the Bahá’í Revelation made with all who recognize Him. The twenty-nine years of ‘Abdu’l-Bahá’s ministry endowed the Bahá’í world with a luminous body of commentary that opens multiple vistas of understanding on His Father’s purpose. In His Will and Testament ‘Abdu’l-Bahá conferred the mantle of Guardian of the Cause and infallible Interpreter of its teachings upon His eldest grandson, Shoghi Effendi, and confirmed the authority and guarantee of divine guidance decreed by Bahá’u’lláh for the Universal House of Justice on all matters "which have not outwardly been revealed in the Book". The Guardianship and the Universal House of Justice can thus be seen to be, in the words of Shoghi Effendi, the "Twin Successors" of Bahá’u’lláh and ‘Abdu’l-Bahá. They are the supreme institutions of the Administrative Order which was founded and anticipated in the Kitáb-i-Aqdas and elaborated by ‘Abdu’l-Bahá in His Will. During the thirty-six years of his ministry, Shoghi Effendi raised up the structure of elected Spiritual Assemblies—the Houses of Justice referred to in the Kitáb-i-Aqdas, now in their embryonic stage—and with their collaboration initiated the systematic implementation of the Divine Plan that ‘Abdu’l-Bahá had laid out for the diffusion of the Faith throughout the world. He also set in motion, on the basis of the strong administrative structure that had been established, the processes which were an essential preparation for the election of the Universal House of Justice. This body, which came into existence in April 1963, is elected through secret ballot and plurality vote in a three-stage election by adult Bahá’ís throughout the world. The revealed Word of Bahá’u’lláh, together with the interpretations and expositions of the Centre of the Covenant and the Guardian of the Cause, constitute the binding terms of reference of the Universal House of Justice and are its bedrock foundation.