If we HAVE to believe it ???
You sound like you dont know what you are talking about.
What the CCC is, is, explaining what a Catholic believes.
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Believe me, Catholics believed it all - even before the CCC was written - or even updated !
Unless this has been overridden, which wouldn't surprise me with Catholicism, then you have to believe it.
PROVIDENTISSIMUS DEUS, ENCYCLICAL OF POPE LEO XIII ON THE STUDY OF HOLY SCRIPTURE, 1893
But first it must be clearly understood whom we have to oppose and contend against, and what are their tactics and their arms. In earlier times the contest was chiefly with those who, relying on private judgment and repudiating the divine traditions and teaching office of the Church, held the Scriptures to be the one source of revelation and the final appeal in matters of Faith.
In the other passages, the analogy of faith should be followed, and Catholic doctrine, as authoritatively proposed by the Church, should be held as the supreme law; for, seeing that the same God is the author both of the Sacred Books and of the doctrine committed to the Church, it is clearly impossible that any teaching can by legitimate means be extracted from the former, which shall in any respect be at variance with the latter. Hence it follows that all interpretation is foolish and false which either makes the sacred writers disagree one with another, or is opposed to the doctrine of the Church.