In recent years, critical discourse concerning the millenarian eschatology of the early Patristic era of Christianity has called into question the common notion that millenarian concepts have been utterly rejected as heretical by the Roman Catholic Church. No Ecumenical Council has ever rejected millenarian eschatology, and papal and juridical statements on the issue have been taken out of context. This essay brings forward, as testing agents, John Henry Newman’s first two notes in Development in order to determine whether Patristic millenarianism, along with a more recently explored version called Eucharistic millenarianism, is a valid example of doctrinal development of an earlier type. Eucharistic millenarianism borrows many aspects from a primitive apostolic source and has been embraced by the Catholic hierarchy, raising the question of how millenarian aspects might legitimately inform contemporary theology. Newman’s theory of the development of doctrine, particularly as seen in his first two notes, is a valuable tool for reevaluating latent concepts that have been unfairly viewed as marginal or even heretical in mainline theological discourse.