What our view of the effectiveness of religion in history does at once make evident as to its nature is—first, its necessary distinction; second, its necessary supremacy. These characters though external have been so essential to its fruitfulness, as to justify the statement that without them religion is not religion. A merged religion and a negligible or subordinate religion are no religion.
Ch. II : The Work of Religion in History, p. 22 - The Meaning of God in Human Experience (1912)