A second major theme of his work is the doctrine of divine adoption in Christ. Again, this idea was not original with Marmion; it is clearly set forth in the New Testament, particularly in the writings of St. Paul. But although the doctrine had been addressed by many spiritual writers before him, "it would be difficult to find another who had given the mystery such preeminence, making it, as he does, the beginning and the end of the spiritual life. And with Dom Marmion it is not so much a theory or a system, as a living truth that acts directly on the soul." Some believe the Catholic Church will one day formally declare Marmion the Doctor of Divine Adoption.