“In a higher world it is otherwise; but here below to live is to change, and to be perfect is to have changed often.” John Henry Newman's celebrated dictum still has the power to startle, coming as it does from a dedicated opponent of liberal Christianity. Newman's conception of Christianity as a “great idea” enabled him to contemplate its interaction with history as a living thing, constantly changing in order to retain its identity. The daring model of Christianity as an “idea,” that is, an impression made upon the imagination, proved incomprehensible to the neo-scholastic mind, which treated the imagination as vastly inferior to the discursive intellect and which saw no reason at all to wrestle with the seemingly intractable problem of how doctrine could preserve its identity as it passed through the cultural vagaries of historical existence. Neo-scholastic ultramontanism saw itself as charged with the custodianship of a fixed and unchangeable deposit; it described the philosophy on which it drew for cognitive self-expression as perennis – that is, valid in and applicable to all ages. The conflict between the concept of Christian doctrines as immutable and perennially valid, on the one hand, and, on the other, as culturally limited expressions of truths which are antecedent to their formulation constitutes the theological core of the Modernist crisis which occurred in the Roman Catholic Church between c. 1890 and 1914.