Book excerpt: The doctrine of the Trinity is one of the most profound and illuminating teachings which, under different names and different forms, is found in many of the great world religions. The triune manifestation of the one Eternal is the fundamental reality of all existence and permeates every single manifestation of life and form both in the wolrd surrounding us and in the world of our inner life. The Third Person the Divine Trinity, the Holy Ghost in Christian terminology, is so crucial to our approach to life that the wonder is the relatively inconspicuous position it has held in Christian dogma. A priest in the Liberal Catholic Church, J. J. Van der Leeuw was in modern terminology, an ecumenical Christian, relating religious concepts from all times and places to the inner teachings of Jesus.