Matthew 16:18, “I say to you, you are Peter, and upon this rock I will build my church.”
or “You, Rocky are the rock upon which I will build my Church.”
In Greek, rock is feminine, Petra, but since Peter is a man, the masculine version of rock has to be used, which is Petros. Petra and Petra both mean the same sized rock. So, Peter is not a piece of the rock. Peter is the same-sized rock as Petra.
Protestants read it as, «As truly as you are called Peter, on this rock of your profession of your faith, I shall build my church.»
The Church is not built on Peter’s faith—there is no mention of Peter’s faith in this verse. Protestants interpret the verse that way because 1 Cor. 3:11 says that Christ is the only foundation.
Thus, many of them say that Peter is a little stone “Petros,” and Jesus is the big, massive stone, “Petra.” However, this is grammatically incorrect because Petros and Petra both mean the same sized rock. If Jesus wanted to use the word “small rock” for Peter, he would have used “psephos” which is mentioned twice elsewhere in the New Testament in Revelation 2:17.
Jesus’ pronouncement is directed to Peter himself and that “Peter” is the nearest antecedent of «this rock” the grammar and logic demand that the identification of «this rock” is no one or nothing else but Peter himself.
Thus, Catholics rightfully believe the papacy is a leadership institution that Jesus set up.
“Ubi Petrus Ibi Ecclesia,” “Where Peter is, there is the Church,” –St. Ambrose (340-397).
Peter said in the Spirit, «You are the Christ, the Son of the living God.» Judaism was not expecting the Messiah to be divine.
Divinely revealed truths by God’s self-revelation that must be believed “credendum” (canon 750, section 1). These must be believed with divine and Catholic faith: Not believing or distorting these entails heresy.
The Nicene creed; Christological dogmas, like the Resurrection; Marian dogmas: Mary is the Mother of God, her Perpetual Virginity; the institution of the sacraments by Christ and their efficacy with grace; the Real and substantial presence of Christ in the Eucharist; the sacrificial nature of the Mass; the foundation of the Church by the will of Christ; the doctrine of the primacy and infallibility of the Roman pontiff; the doctrine of original sin; the doctrine of the immortality of the spiritual soul and on the immediate recompense after death; the absence of error in the Bible; the grave immortality of direct and voluntary killing of an innocent human life, etc. This is a partial listing of infallible truths.
There are also truths that are necessarily connected with revealed truths (the Latin word is “Tenendum,” to have and to hold (canon 750, section 2). Believing in these is necessary to remain in Communion with the Catholic Church, like the reservation of priestly ordination to men, the illicitness of in vitro fertilization (IVF) and artificial birth control like the pill and other means; the illicitness of prostitution, pornography, and fornication; the legitimacy of the election of the supreme pontiff; the celebration of an ecumenical council like Vatican II; the canonization of saints; and the declaration on the invalidity of Anglican ordinations.
Lastly, there are authoritative, but not definitive or infallible teachings set forth by the authentic ordinary magisterium in a non-definitive way, which call for the religious obedience of submission of the intellect and will (canon 752), like papal encyclicals on various topics, the documents of Vatican II, etc.
The entire people of God share in the prophetic role of Christ, and he relies heavily on you to transmit the teachings of the Catholic faith and your reward will be great in heaven for faithfully doing so.