The Development of Doctrine in the Roman Catholic faith vs the Orthodox faith.
The Orthodox Church does not endorse the view that the teachings of Christ have changed from time to time; rather that Christianity has remained unaltered from the moment that the Lord delivered the Faith to the Apostles (Matt. 28: 18-20). She affirms that "the faith once delivered to the saints" (Jude 3) is now what it was in the beginning. Orthodox of the twentieth century believe precisely what was believed by Orthodox of the first, the fifth, the tenth, the fifteenth centuries.
To be sure, Orthodoxy recognizes external changes (e.g., vestments of clergy, monastic habits, new feasts, canons of ecumenical and regional councils, etc.), but nothing has been added or subtracted from her Faith. The external changes have a single purpose: To express that Faith under new circumstances. For example, the Bible and divine Services were translated from Hebrew and Greek into the language of new lands; or new religious customs arose to express the ethnic sensibilities of the converted peoples, etc.; nevertheless, their has always been "one faith, one Lord, one baptism" (Eph. 4: 4).
The fundamental witness to the Christian Tradition is the holy Scriptures; and the supreme expositors of the Scriptures are the divinely inspired Fathers of the Church, whether the Greek Fathers or Latin Fathers, Syriac Fathers or Slavic Fathers. Their place in the Orthodox religion cannot be challenged. Their authority cannot be superseded, altered or ignored.
On the other hand, Roman Catholicism, unable to show a continuity of faith and in order to justify new doctrine, erected in the last century, a theory of "doctrinal development."
Following the philosophical spirit of the time (and the lead of Cardinal Henry Newman), Roman Catholic theologians began to define and teach the idea that Christ only gave us an "original deposit" of faith, a "seed," which grew and matured through the centuries. The Holy Spirit, they said, amplified the Christian Faith as the Church moved into new circumstances and acquired other needs.
Consequently, Roman Catholicism, pictures its theology as growing in stages, to higher and more clearly defined levels of knowledge. The teachings of the Fathers, as important as they are, belong to a stage or level below the theology of the Latin Middle Ages (Scholasticism), and that theology lower than the new ideas which have come after it, such as Vatican II.
All the stages are useful, all are resources; and the theologian may appeal to the Fathers, for example, but they may also be contradicted by something else, something higher or newer.
On this basis, theories such as the dogmas of "papal infallibility" and "the immaculate conception" of the Virgin Mary (about which we will say more) are justifiably presented to the Faithful as necessary to their salvation.
In any case, the truth of these dogmas have always belonged to the Christian Tradition. They have been present from the beginning of that Tradition as "hints," seeds that only waited for the right time to bloom.