Here is a very good take on Saint Vincent of Lérins (+445) and the complex question of the development of doctrine, on which Saint John Henry Cardinal Newman also wrote a millennium and a half after Vincent, in his own superb and carefully delineated essay. We are in dire need of such precise and clear teaching in our Church, mired in diffuse and ambiguous tapioca theology, providing no defense from the onslaught of the subtlety of the Evil One.
Saint Vincent penned his own essay, the Commonitorum, in 434, a few years after the Council of Ephesus (431), which proclaimed Our Lady as ‘Theotokos’, the Mother of God, contrary to Nestorius, who denied this title (in accord with his prior heresy that Christ was ‘two persons’, human and divine). This term is not found explicitly in Scripture, but is fully in accord with its teaching, and helps to clarify the truth, by means of philosophical terms.
In a word, doctrine can only ‘develop’ organically, in accord with what has come before, to what Christ revealed to His Apostles to safeguard and hand on, and never contrary to it. Truth cannot contradict truth, nor can one present Magisterium abrogate a former one. Christ’s Church is a universal entity, living in history, but also transcending its vagaries. The Church is the ‘pillar and bulwark’ or truth, as Saint Paul says. So, dear reader, as much as you might, immerse yourself in that truth, going back two thousand years. It’s the best antidote against heresy, and being led astray by ravenous wolves, or even muddled shepherds. +