7 The heavenly doctrine of Christ, although for the most part committed to writing by divine inspiration, could not unite the minds of men if left to the human intellect alone. It would, for this very reason, be subject to various and contradictory interpretations. This is so, not only because of the nature of the doctrine itself and of the mysteries it involves, but also because of the divergencies of the human mind and of the disturbing element of conflicting passions. From a variety of interpretations a variety of beliefs is necessarily begotten; hence come controversies, dissensions and wranglings such as have arisen in the past, even in the first ages of the Church. Irenaeus writes of heretics as follows: "Admitting the sacred Scriptures they distort the interpretations" (Lib. iii., cap. 12, n. 12). And Augustine: "Heresies have arisen, and certain perverse views ensnaring souls and precipitating them into the abyss only when the Scriptures, good in themselves, are not properly understood" ( In Evang . Joan ., tract xviii., cap. 5, n. I). Besides Holy Writ it was absolutely necessary to insure this union of men's minds - to effect and preserve unity of ideas - that there should be another principle. This the wisdom of God requires: for He could not have willed that the faith should be one if He did not provide means sufficient for the preservation of this unity; and this Holy Writ clearly sets forth as We shall presently point out. Assuredly the infinite power of God is not bound by anything, all things obey it as so many passive instruments. In regard to this external principle, therefore, we must inquire which one of all the means in His power Christ did actually adopt. For this purpose it is necessary to recall in thought the institution of Christianity.
Source: Satis Cognitum (Vatican.va)