Why do I accept the Catholic Church and its teachings? Here is my fundamental reason:
Christianity, as a historical revelation, has been handed down to us through history by the Church. I have no authority to change it. In the early Church, the basic outlines of Christianity were worked out--the basic beliefs of the faith (such as the Trinity, the two natures of Christ, etc.), the canon of Scripture, the belief in the validity of certain extra-biblical traditions (such as using oil in Confirmation, the sign of the cross, etc.), a belief in the authority of the Church guided by the Holy Spirit. These developments were organic, and the historic Church's testimony has been that these developments have been guided by the Holy Spirit. All of these developments are woven together. To try to take one piece of them without the others is to arbitrarily divide what has been handed down to us as a seamless garment. Christ has commanded us to obey the shepherds he appointed over us in the Church--and we see in Scripture and in Church history that Christ appointed the apostles to lead the Church, and they appointed elders/bishops to continue to guide the Church after them. Christ also commanded his people to keep unity in the Church. At the least, these things imply that we should not break the unity of the Church or reject the authority of its shepherds without proof that we have good cause to do so. In order to accept part of the Church's Tradition while rejecting other parts (such as, for example, accepting the Bible while rejecting the Church's extra-biblical traditions or its authority), I would have to rebel against the established teachings of the historic Church, disobeying its established shepherds and tearing its unity. In fact, that is precisely what happened in the Protestant Reformation (as Protestant writer Carl Trueman articulates well). In order for Martin Luther and the other reformers to maintain Sola Scriptura and their other distinctive ideas and practices, they had to rebel against the established Catholic Church which had organically grown from the early Church and break its unity. They believe they were justified in doing this, but I see no clear, non-question-begging basis for affirming Sola Scriptura or other distinctive Protestant doctrines. Therefore, since I have no basis to reject what has been handed down from the historic Church, I must embrace Catholic faith and unity.
The central point is this: I did not invent Christianity. It is a historical revelation that has come to me. I believe I have good reasons to think it to be true. I have no basis or authority to make it something other than what it is as I have received it. Therefore, I cannot go with the Protestant Reformation and its attempt to reinvent the Christian faith in opposition to its historic formulation and historic communion. Therefore, I am Catholic. Of course, much unpacking can and ought to be done at various specific points in what I am saying (and some of that is done in the articles in the above embedded links and in the links provided below), but that is the basic argument.
For more, see above embedded links, and see my narrative account of the intellectual developments that led ultimately to my conversion to Catholicism. See also my fictional dialogue with a Protestant.