Four words of S Vincent of Lerins: 'Development' in the Christian Church and in her Doctrine: Development must take place eodem sensu eademque sententia [keeping the same meaning and the same judgment/opinion]. (In the Liturgy of the Hours the whole passage can be found in Vol IV.)
This phrase has a big place in the Conciliar Magisterium. It appeared (para 62) in Gaudium et Spes, and even before that it lay at the heart of the address by B John XXIII at the start of the Council. But here it is necessary to avoid a dangerous tripwire. In the popular English paperback collection of Conciliar documents (Chapman) edited by W M Abbott, a misleading paraphrase of this speech is given in which the phrase is totally omitted. This became the occasion of an important correspondence in the Tablet in December 1991, in the course of which Professor John Finnis of this University demonstrated conclusively that Peter Hebblethwaite's Pope John XXIII (p 432) is guilty of gross errors. Hebblethwaite, a failed Jesuit, fabricated a story about how some 'brave' and liberal words of John XXIII in his adddress to the Council were distorted, in a curial plot, by the later addition, in publication, of the words I quote. The papal address did not, according to Hebblethwaite, originally contain them. This gross distortion of events promptly became part of the mythology of the 'liberals', being cited as fact by Basil Hume and [the present Bishop of Guildford] Christopher Hill.
This passage by S Vincent lies at the heart of Newman's Essay on Development, which straddles his life as an Anglican and as a Roman Catholic (Chapter 5 Section 1). Its presence in the post-Conciliar Liturgia Horarum marks it as a part of the Conciliar documents which remains the everyday Magisterium of the modern Chuch. Some members of SSPX sometimes disparagingly call that Church the 'Conciliar Church'. But a rebuttal of such sneers is best achieved by disseminating the facts about what John XXIII and Gaudium et Spes actually said; and how the Liberals have got away with distorting it.