Truth in Religion: the Plurality of Religions and the Unity of Truth Reprint edition Mortimer J. Adler

Only if, with regard to the diversity of religions, there are questions about truth and falsehood do we have a problem about the pluralism of religions and the unity of truth.

That problem is not concerned with preserving religious liberty, freedom of worship, and the toleration, in a particular society or in the world, of a diversity of religious institutions, communities, practices, and beliefs. It is concerned only with the question of where, in that diversity, the truth lies if there is any truth in religion at all.