what are secular historians saying when it comes to the catholic claims of being the original christian church? Are they in agreement with the catholic position?
Back when I was in college, at that time most universities had undergrad courses in the History of Western Civilization, or History of European Civilization. Nowadays, that may be considered a little eurocentric, for some reason.
Nevertheless, even in secular universities, the history of western civilization consisted largely of the history of the Catholic Church. It was unavoidable. One of my cousins (non-catholic) once commented to me after his first year at secular university, “I didn’t realize that before the 1500’s everybody was Catholic!”
Those courses generally traced the Roman, Greek, and Jewish influences on the secular ancient world, culminating in the rise of Christianity (i.e. Catholicism) followed by the largely Catholic history up until the Reformation and the various subsequent political revolutions.
Real historians are neither secular nor Catholic. They start from valid documents.
Historians can research on subjects like whether Peter was ever in Rome, but they can’t rule on whether that has to do with anything related to faith.
Catholics historians have erred and non-Catholic or non-religious historians have erred,usually because they started from their convictions and not from valid documents.
A historian is not an apologists, though apologists can use true history,