Catholic Apologetics is similar to the greater category of Christian apologetics in that it defends and explains the beliefs of the Christian faith in general, but different in that it defends the beliefs of the Catholic Church in particular.
Since the Reformation, the Catholic Church rejected the teaching that everything that can be known about Christianity can be found in the Bible. The Church cites the simple fact that those who promote Sola Scriptura in principle don't follow it in practice, adding their own theology to the scriptures. Furthermore, no verse that appears to promote the Bible alone comes without a reference to Tradition. (See 2 Tim. 3:13-15, 2 Thess. 3:6, 1 Cor. 11:2). Second, Sola Scriptura can only work if the Bible's writers don't refer to anything outside the canon. Yet, Paul refers to a letter to the Corinthians not found in the Bible (1 Cor. 5:9-11), a letter to Laodicea also not found in the Bible (Col. 4:16), quotes an ancient Greek poet (Acts 17:28) and James refers to a verse not found in the Old Testament (James 4:5). Third, this belief could only be right if the Bible was self-explanatory. If so, some Catholics argue, why then does the Bible see the need for a guide? (See 2 Peter 1:20 and 2 Peter 3:15-16).
Catholics believe Jesus chose Peter as the leader of the Apostles and derive the belief from the following passages: Matt 16:18-19, Isaiah 22:20-22, John 21:15-17, Luke 12:41, Luke 22:31-32 The belief stems from the obvious facts that Simon's name is changed and thus anytime God changes someone's name, that person becomes a significant individual; ancient Jews recognized the keys in question as symbols of authority; and the fact that Peter makes leadership decisions in the New Testament such as initiating a successor to Judas (Acts 1:15), working the first healing after Pentecost (Acts 3:6-7), the first to announce there is no salvation other than through Jesus (Acts 4:8-12) not requiring male converts to be circumcised (Acts 15:7-12), and makes a judgment call on Paul's letters (2 Peter 3:16).