The above word usually refers to the teaching authority of the Roman Catholic Church which implies the guarantee of truth and infallibility promised by Our Lord Jesus Christ to St. Peter, the first Pope. “Simon, son of Jonah, you are a happy man! Because it was not flesh and blood that revealed this to you but my Father in heaven. So I now say to you: You are Peter and on this rock I will build my Church. And the gates of the underworld can never hold out against it. I will give you the keys of the kingdom of heaven: whatever you bind on earth shall be considered bound in heaven; whatever you loose on earth shall be considered loosed in heaven.” (Mt. 16:18-20).
Church magisterium is thus delineated this way: The solemn or the ordinary magisterium of the Church is the norm of faith in truths revealed by God. The solemn magisterium consists of papal or conciliary dogmatic definitions. The ordinary magisterium is the unanimous teaching of the bishops united with the Pope (cf. Canon Law 748-749). For the same reason as above, the daily ordinary uniform teaching of the Church in every place in the whole world is infallibly true because it is one with the universal Catholic Church under the successor of Peter and the Bishops united with him.
Canon 748 – [1.]. All persons are bound to seek the truth in those things which regard God and his Church and by virtue of divine law are bound by the obligation and possess the right of embracing and observing the truth which they have come to know. [2.] No one is ever permitted to coerce persons to embrace the Catholic faith against their conscience.
Canon 749 - [1.] By virtue of his office, the Supreme Pontiff possesses infallibility in teaching when as the supreme pastor and teacher of all the Christian faithful, who strengthens his brothers and sisters in the faith, he proclaims by definitive act that a doctrine of faith or morals is to be held. [2.] The college of bishops also possesses infallibility in teaching when the bishops gathered together in an ecumenical council exercise the magisterium as teachers and judges of faith and morals who declare for the universal Church that a doctrine of faith or morals is to be held definitively; or when dispersed throughout the world but preserving the bond of communion among themselves and with the successor of Peter and teaching authentically together with the Roman Pontiff matters of faith or morals, they agree that a particular proposition is to be held definitively. [3.] No doctrine is understood as defined infallibly unless this is manifestly evident.
In the confused teachings of our world, the divergent doctrines, and the malicious errors that originate from the Devil who is “a murderer and the father of lies” (Jn. 8:44), we need the guiding light of the Roman Catholic Church to guide us towards love, purity, morality, justice and righteousness and reach the final destiny we all aim for – heaven with God as Our Father, source of every good and happiness. Jesus, being God’s only begotten Son, knew how necessary is that guarantee of protecting the Church from wrong teachings since He Himself gave that final instruction for the Church and its missionaries. “Go into the whole world and preach the gospel to every creature. He who believes and is baptized will be saved; he who does not believe will be condemned” (Mk. 16:16). The universal body of the faithful who have received the anointing of the holy one (see 1 Jn. 2:20,27) cannot be mistaken in belief (Lumen Gentium 12).