A good example of this irrational block is a discussion of transubstantiation. An ignorant Protestant might think we believe that the bread and wine are transformed physically into human flesh and blood. When the true explanation is given and Scriptural support is offered and a reasonable belief is given the response is often simply to change the subject. Either that or the Protestant thinks the Catholic is being tricky and “Jesuitical” and offering a version of Catholic belief which is not really what Catholics believe. It’s hard to let go the misunderstanding conceived within an atmosphere of prejudice.
The same applies to the Catholic doctrine of papal infallibility. In this one however, the subject can be approached from a new angle: Instead of simply defending and defining papal infallibility it is not a bad idea to ask the Protestant if he can find any example of the Catholic Church being in error. This has to be framed carefully within the definition of papal infallibility. The infallibility of the pope is really the infallibility of Christ’s Church–the simple belief that in matters of faith and morals–where there is a formally defined teaching–the Church does not err. Therefore, within those restrictions ask the Protestant for an example where the church has erred. Can he find one?
Of course he may feel that the Catholic Church has erred in any number of doctrinal ways, but he must take the time to find out what the church really teaches about that doctrine–and not assume he knows what the Catholic Church teaches. He has to refer to Church documents–not just hearsay or misunderstandings of non Catholics.
There is one other point to be made. One should ask the Protestant if there is any Christian doctrine that he believes in necessary to be held for a soul’s salvation. If there is even one such doctrine, then (whether he admits it or not) he believes in an infallible authority–that is an authority that can be trusted to define a particular belief as mandatory dogma and to do so without error. If he ascribes to even one such dogma, then we must ask what authority defined that dogma, where it came from and why he believes it to be without error. If he says that the authority for that belief is the Sacred Scripture he has only moved the goalpost for he must then answer why he believes Sacred Scripture to be infallible, and who and when defined the canon of Sacred Scripture and taught him that it was infallible.