Introduction: I've said before that I am not a Catholic apologist. I tend to spend little to no time in consideration of protestant faiths. Unfortunately I did go to a Lutheran High School so did study Martin Luther's heresies for 4 years. As a result of this I came back to the Truth in the Catholic Church. I have experienced first hand the errors of protastantism and shun them like the plague they are. Anyway, I read a fine reading called "Against the Reformers" by St. Alphonsus Ligouri. Beautiful, simple title is it not? I'll post it in parts and God bless you.
Against the Reformers
"A church which is not one in its doctrine and faith can never be the True Church. Hence, because truth must be one, of all the different churches, only one can be the true one, and outside of that Church there is no salvation. "
"Now, in order to determine which is this one true Church, it is necessary to examine which is the Church first founded by Jesus Christ, for when this is ascertained, it must be confessed that this one alone is the true Church which, having once been the true Church must always have been the true Church and must forever be the true Church. For to this first Church has been made the promise of the Savior that the gates of Hell would never be able to overturn it [Matt 16:18]. "
"In the entire history of religion, we find that the Roman Catholic Church alone was the first Church, and that the other false and heretical churches afterwards departed and separated from her. This is the Church which was propagated by the Apostles and afterwards governed by pastors whom the Apostles themselves appointed to rule over her. This character can be found only in the Roman Church, whose pastors descend securely by an uninterrupted and legitimate succession from the Apostles of the world [Matt 28:20]. "
St Alphonsus Mary De Liguori (1696-1787) Bishop and Doctor of the Church