Extrapolating from the wearying context, the distinction Ed Peters draws in this post is an interesting one:
Now, although in popular parlance people associate the concept of "infallibility" with teachings to be believed by the faithful, in fact, infallibility also extends to teachings to be "firmly embraced and retained" by the faithful. The difference between the two is not in the degree of certitude to be accorded these distinct kinds or levels of teachings, nor in the degree of irreformability with which each are set forth, but rather, in the virtue by which the faithful come to accept these two types of teachings: through belief in the forever-completed revelation of the Word of God in the former, and through confidence in the continuing guidance of the Holy Spirit in the latter.
There are three words we commonly use together, and they mean almost the same thing, but not quite: hope, trust and confidence. Hope is the assured desire that we shall obtain some future good thing. Trust is the reliance we have on someone that what we hope for we shall obtain. Without trust there can be no hope. We hope to get things, ah yes, but only because we trust someone to give us those things. Confidence is the result of hope and trust. It is the peace of heart that comes from the security which is the result of having an assured hope and a firm trust. We can have confidence only if we first trust, and trusting have hope.
It's a bit... non-self-evident, perhaps, that confidence in God should cause a firm embrace and retention of definitive propositions of the magisterium of the Church. But the question isn't whether we're going to firmly embrace and retain definitive propositions; the question is whose propositions are we going to embrace, and why.