I recently came across a critic of Protestantism who made the common assertion that we need an infallible source to tell us what canon of scripture to follow. Apparently, we're supposed to think that fallibly applying some general principles from an infallible source in order to arrive at a canon isn't enough. This critic of Protestantism seemed to be suggesting that we need an infallible source to do something like list the canonical books for us. Supposedly, it's too difficult to discern a canon without such guidance. And so on.
Part of what we should keep in mind when issues like those come up is that the manner in which Protestants handle those canonical issues is substantially the same as how they handle canonical issues in contexts other than scripture and how such critics of Protestantism handle canonical issues in many contexts in their lives. We all accept canons for the writings of various historical figures (Tacitus, Justin Martyr, George Washington, etc.) without any sort of infallible ruling on the subject, for example. There are ongoing disagreements among critics of Protestantism about which extrabiblical traditions are part of the Christian rule of faith and which aren't, such as which papal teachings qualify as an exercise of papal infallibility and which don't. Those non-Protestants aren't relying on an infallible list, just as they arrive at a lot of other canons in other contexts in life without any infallible list. For further discussion of topics like these, see here and here, among other posts.
