Oneness of Religion
The principle of the unity of religion is at the center of Baha'i teachings. Bahá’u’lláh states that humanity is engaged in a collective growth process quite similar to the growth process of an individual: just as a person begins life as a helpless infant and attains maturity in successive stages, so humankind began its collective social life in a primitive state, gradually attaining maturity. In the case of the individual, it is clear that his or her development takes place as a result of the education he or she receives from parents, teachers, and society in general.
But what is the motive force in humankind’s collective evolution? The answer the Bahá’í Faith provides to this question is “revealed religion.” In one of His major works, the Kitab-i-Iqan (the Book of Certitude), Bahá’u’lláh explained that God, the Creator, has intervened and will continue to intervene in human history by means of chosen Messengers. These Messengers, Whom Bahá’u’lláh called “Manifestations of God ,” are principally the Founders of the major revealed religions, such as Abraham, Moses, Buddha, Zoroaster, Jesus, Muhammad, and so forth. It is the spirit released by the coming of these Manifestations, together with the influence of Their teachings and the social systems established by Their laws and precepts, that enable humankind to progress in its collective evolution. Simply put: the Manifestations of God are the chief educators of humanity. Thus the principle of the unity of religion means that all of the great religious Founders—the Manifestations—have come from God, and that all of the religious systems established by Them are part of a single divine plan directed by God.
In reality, there is only one religion, the religion of God. This one religion is continually evolving, and each particular religious system represents a stage in the evolution of the whole.
“The fundamental principle enunciated by Bahá’u’lláh, the followers of His Faith firmly believe, is that Religious truth is not absolute but relative, that Divine Revelation is a continuous and progressive process, that all the great religions of the world are divine in origin, that their basic principles are in complete harmony, that their aims and purposes are one and the same, that their teachings are but facets of one truth, that their functions are complementary, that they differ only in the non-essential aspects of their doctrines and that their missions represent successive stages in the spiritual evolution of human society.”— Shoghi Effendi