Here we have clearly laid down another great principle, that of the Development of Christian Doctrine.
Progress and growth, whether in the natural or supernatural order, involve no essential change, for in the various stages of life there is always preservation of complete identity. Further, it is well known that the definition of doctrine has resulted in great measure from the gainsaying of heretics. At first, Christian truths were taught as propositions undeveloped in their implications—for example, " Christ is true God;" or again, " Christ is true Man." But when the revealed doctrine was insidiously assailed, it became necessary to draw it out in its various bearings and then to formulate it in clear-cut definition which would preclude the possibility of error. Such is the office of the Teaching Church.
In this way it came to pass that the Arian, Apollonian, Nestorian, Eutychian and Monothelite heresies have been the occasion of furnishing us with those categorical and immutable affirmations of the Councils and the Creeds, which, immediately upon their promulgation, became for all the ages that were to follow the very touchstone of the Faith. No new doctrine was discovered, as heretics have idly dreamed, at Nicaea, Ephesus and Chalcedon, or in after years at Florence, Trent and the Vatican—it was the old doctrine handed down from the Apostles but stated in the face of error with scientific fulness and precision. Stone was carefully laid upon stone, each to rest immovable, until at last, standing foursquare against all winds and storms, arose the majestic Temple of Catholic Truth, as it is visible to all men to-day. This process of growth and building, under the watchful eye of the Church, receiving the seal of her sanction and approval, is what is meant in general by the Development of Christian Doctrine.
Now, the interesting question arises. How far has there been such a process of development in connection with Catholic of doctrine concerning the Mother of our Lord and with the devotion which is the outcome of that doctrine ?
Cardinal Newman has written as follows:
"I fully grant that devotion towards the Blessed Virgin has increased amongst Catholics with the progress of centuries; I do not allow that doctrine concerning her has undergone a growth, for I believe that it has been in substance one and the same from the beginning." (Answer to Dr. Pusey s Eirenicon, p. 28.)