48 Since faith is one, it must be professed in all its purity and integrity. Precisely because all the articles of faith are interconnected, to deny one of them, even of those that seem least important, is tantamount to distorting the whole. Each period of history can find this or that point of faith easier or harder to accept: hence the need for vigilance in ensuring that the deposit of faith is passed on in its entirety (cf. 1 Tim 6:20) and that all aspects of the profession of faith are duly emphasized. Indeed, inasmuch as the unity of faith is the unity of the Church, to subtract something from the faith is to subtract something from the veracity of communion. The Fathers described faith as a body, the body of truth composed of various members, by analogy with the body of Christ and its prolongation in the Church. The integrity of the faith was also tied to the image of the Church as a virgin and her fidelity in love for Christ her spouse; harming the faith means harming communion with the Lord. The unity of faith, then, is the unity of a living body; this was clearly brought out by Blessed John Henry Newman when he listed among the characteristic notes for distinguishing the continuity of doctrine over time its power to assimilate everything that it meets in the various settings in which it becomes present and in the diverse cultures which it encounters, purifying all things and bringing them to their finest expression. Faith is thus shown to be universal, catholic, because its light expands in order to illumine the entire cosmos and all of history.
Source: Lumen Fidei (Vatican.va)