The Problem of Authority
The different religious communities have failed to unite in the past, because the adherents of each have regarded the Founder of their own community as the one supreme authority, and His law as the divine law. Any Prophet Who proclaimed a different message was, therefore, regarded as an enemy of the truth. The different sects of each community have separated for similar reasons. The adherents of each have accepted some subordinate authority and regarded some particular version or interpretation of the Founder’s Message as the One True Faith, and all others as wrong. It is obvious that while this state of matters exists no true unity is possible. Bahá’u’lláh, on the other hand, teaches that all the Prophets were bearers of authentic messages from God; that each in His day gave the highest teachings that the people could then receive, and educated men so that they were able to receive further teachings from His successors. He calls on the adherents of each religion, not to deny the Divine Inspiration of their own Prophets, but to acknowledge the Divine Inspiration of all other Prophets, to see that the teachings of all are essentially in harmony, and are parts of a great plan for the education and the unification of humanity. He calls on the people of all denominations to show their reverence for their Prophets by devoting their lives to the accomplishment of that unity for which all the Prophets labored and suffered.
John E. Esslemont, "Bahá’u’lláh and the New Era"