“Because, as a man ought to obey a lower power in those things only which are not opposed to the higher power; so even a man ought to adapt himself to the rule in all things according to its mode; on the other hand, a man ought to adapt himself to the secondary rule in those things which are not at variance with the primary rule: because in those matters in which it is at variance, it is not a rule:
On that account, one is not to give assent to the preaching of a prelate which is contrary to the faith since in this it is discordant with the primary rule. Nor through ignorance is a subject excused from the whole: since the habit of faith causes an inclination to the contrary, since it teaches necessarily of all things that pertain to salvation.”1
This is actually an important paragraph, because it gives an indication of what to do if a member of the magisterium errs. The Magisterium is the secondary rule of faith, the Tradition is the primary rule. Normally those two should be in accord, but if they are not, you always default to the primary rule, not to the current magisterium. This is the difference between Trads and the Neo-cons, the latter chuck the tradition if there is any variance and go with the secondary rule, namely the current magisterium. It remains to be seen whether Francis’ slight against the teaching of John Paul II will wake them up or not.
1 Quod sicut homo debet obedire inferiori potestati in his tantum in quibus non repugnat potestas superior; ita etiam debet homo se primae regulae in omnibus commensurare secundum suum modum; secundae autem regulae debet se homo commensurare in his in quibus non discordat a prima regula: quia in his in quibus discordat, jam non est regula; et propter hoc praelato contra fidem praedicanti non est assentiendum, quia in hoc discordat a prima regula. Nec per ignorantiam subditus excusatur a toto: quia habitus fidei facit inclinationem ad contrarium, cum necessario doceat de omnibus quae pertinent ad salutem.” Super Sent., lib. 3 d. 25 q. 2 a. 1 qc. 4 ad 3