But what if a pope did teach heresy ex cathedra?

ustin Lat­ti­more, a Protes­tant, asked the ques­tion on Face­book. Ear­li­er today, Dave Arm­strong also blogged about it. Mr. Arm­strong, in deny­ing the pos­si­bil­i­ty of ex cathe­dra heresy, still hedges a bit:

To get real­ly philo­soph­i­cal­ly heavy [Dear God.], at this point I would deny (in faith) that it could hap­pen, but I don’t think it is an “impos­si­ble coun­ter­fac­tu­al” or “log­i­cal­ly impos­si­ble” in all pos­si­ble or con­ceiv­able worlds. [No, not all of them.] It’s the dif­fer­ence between phi­los­o­phy and faith. In faith, I don’t believe it ever would or could hap­pen in fact.

But it could in oth­er worlds? Real­ly?

Now, as I see it, this is like ask­ing, “But what if God had made a round square?” There are no round squares. Round squares are log­i­cal­ly impos­si­ble. And there is no oth­er world in which the log­i­cal­ly impos­si­ble exists. I don’t like to get into quan­tum apolo­get­ics.

God does not give us a Church, if he gives us a Church at all (cf. Matt. 16:18), that can teach error. End stop. Let us con­sult Sacred Scrip­ture on this point.

John 16:13. When the Spir­it of truth comes, he will guide you into all the truth; for he will not speak on his own author­i­ty, but what­ev­er he hears he will speak, and he will declare to you the things that are to come.

1 Tim. 3:15. If I am delayed, you may know how one ought to behave in the house­hold of God, which is the church of the liv­ing God, the pil­lar and bul­wark of the truth.

God does not make a round square, and he does not make a bul­wark of truth that teach­es false­hood. Christ builds the Church on Peter, and he can not give us a Church that will err.

The Church too tells us that a pope can not—no, not ever—teach error ex cathe­dra. Here is Vat­i­can I:

We teach and define as a divine­ly revealed dog­ma that when the Roman Pon­tiff speaks ex cathe­dra, that is, when, in the exer­cise of his office as shep­herd and teacher of all Chris­tians, in virtue of his supreme apos­tolic author­i­ty, he defines a doc­trine con­cern­ing faith or morals to be held by the whole Church, he pos­sess­es, by the divine assis­tance promised to him in blessed Peter, that infal­li­bil­i­ty which the divine Redeemer willed his Church to enjoy in defin­ing doc­trine con­cern­ing faith or morals.

God does not make a round square, and God does not make a fal­li­bly infal­li­ble pope.

But let us look fur­ther, to the wery Cat­e­chism of the Church.

889. In order to pre­serve the Church in the puri­ty of the faith hand­ed on by the apos­tles, Christ who is the Truth willed to con­fer on her a share in his own infal­li­bil­i­ty. By a “super­nat­ur­al sense of faith” the Peo­ple of God, under the guid­ance of the Church’s liv­ing Mag­is­teri­um, “unfail­ing­ly adheres to this faith.

890. The mis­sion of the Mag­is­teri­um is linked to the defin­i­tive nature of the covenant estab­lished by God with his peo­ple in Christ. It is this Mag­is­teri­um’s task to pre­serve God’s peo­ple from devi­a­tions and defec­tions and to guar­an­tee them the objec­tive pos­si­bil­i­ty of pro­fess­ing the true faith with­out error. [God does not make a round square; God does not give an uncer­tain guar­an­tee.] Thus, the pas­toral duty of the Mag­is­teri­um is aimed at see­ing to it that the Peo­ple of God abides in the truth that lib­er­ates. To ful­fill this ser­vice, Christ endowed the Church’s shep­herds with the charism of infal­li­bil­i­ty in mat­ters of faith and morals. [A pope can not teach error because he is pro­tect­ed from it by God.] The exer­cise of this charism takes sev­er­al forms:

891. The Roman Pon­tiff, head of the col­lege of bish­ops, enjoys this infal­li­bil­i­ty in virtue of his office, when, as supreme pas­tor and teacher of all the faithful—who con­firms his brethren in the faith he pro­claims by a defin­i­tive act a doc­trine per­tain­ing to faith or morals. … The infal­li­bil­i­ty promised to the Church is also present in the body of bish­ops when, togeth­er with Peter’s suc­ces­sor, they exer­cise the supreme Mag­is­teri­um,” above all in an Ecu­meni­cal Coun­cil. When the Church through its supreme Mag­is­teri­um pro­pos­es a doc­trine “for belief as being divine­ly revealed,” and as the teach­ing of Christ, the def­i­n­i­tions “must be adhered to with the obe­di­ence of faith.” This infal­li­bil­i­ty extends as far as the deposit of divine Rev­e­la­tion itself.

892. Divine assis­tance is also giv­en to the suc­ces­sors of the apos­tles, teach­ing in com­mu­nion with the suc­ces­sor of Peter, and, in a par­tic­u­lar way, to the bish­op of Rome, pas­tor of the whole Church, when, with­out arriv­ing at an infal­li­ble def­i­n­i­tion and with­out pro­nounc­ing in a “defin­i­tive man­ner,” they pro­pose in the exer­cise of the ordi­nary Mag­is­teri­um a teach­ing that leads to bet­ter under­stand­ing of Rev­e­la­tion in mat­ters of faith and morals. To this ordi­nary teach­ing the faith­ful “are to adhere to it with reli­gious assent” which, though dis­tinct from the assent of faith, is nonethe­less an exten­sion of it.

God gives us an infal­li­ble teach­ing Church. That is a guar­an­tee. There is no “but what if?” And not only does the pope have infal­li­bil­i­ty ex cathe­dra: Church coun­cils have it, and the bish­ops who teach in union with the Church have it.

It is just not pos­si­ble for a pope to teach error. It has not hap­pened and it can’t hap­pen. End stop. It would mean that the Holy Spir­it does not guide the Church into all truth, which would make Jesus a liar when he speaks to the apos­tles in John 16:13.

If some­one does think it is a pos­si­bil­i­ty for the pope to teach error ex cathe­dra, then it is point­less to start spec­u­lat­ing about hypo­thet­i­cal oth­er worlds in which God can make a round square or a bul­wark of truth that errs. Direct me to a pope who has taught error ex cathe­dra. We’ve had 266 of them; there’s 2000 years of data. Search.