Thank you for that admission. It then, however, undercuts every argument that I've ever seen other Catholics use to try to support the church.
How so?
If one considers the Bible simply as a historical document, one can see Christ establishing a church against which the gates of hell would not prevail (Mat 16:19), and declaring it authoritative in settling disputes. (Mat 18:17).
In a logical sense, how could the Bible tell us whether today's Catholic Church is the Church that Christ founded? I suppose an Apostle could have written that "in the year 2013, the church that will be headed by Pope Francis is the Church that Christ founded." But the Apostles didn't do that.
To determine whether today's Catholic Church is the Church that Christ founded, one simply has to examine the historical record. It's obvious to me that the Catholic Church can trace Its origin to Apostolic times. But I can't do the historical research for you or anyone else.
But as Cardinal Newman said, "to be deep in history is to cease to be Protestant."