The Bahá'í principle of religious unity is unique among the world's religious traditions in that its primary basis is found within its own sacred texts and not in commentaries of those texts. The Bahá'í principle affirms the existence of a common transcendent source from which the religions of the world originate and receive their inspiration. The Bahá'í writings also emphasize the process of personal transformation brought about through faith as a unifying factor in all religious traditions. The apparent differences between the world's religious traditions are explained by appealing to a perspectivist approach grounded in a process metaphysics. For this reason, I have characterized the Bahá'í view as "process perspectivism". Radical pluralism is the greatest philosophical challenge to the Bahá'í principle of religious unity. The main criticisms made by the radical pluralists are briefly examined.