I'd like to thank @F M Shyanguya for starting a "counter-post" to answer @Gesù è con noi's falsehoods, I'll post here since I've been maligned as well.

The First Vatican Council condemned the modernist heresy (which it spreads by @Ultraviolet and @F M Shyanguya ) that the pope can err as a private doctor.

First, I have never used the term "private doctor" so right from the get-go @Gesù è con noi is factually wrong. I'm not sure how Gesu even defines a "private doctor" (as opposed to, say, a public doctor). The noun "doctor" in English usually refers to a medical profession.

Gesu makes the claim...
On July 18, 1870, Pius IX, the pope of infallibility, anathematizes every person who dares to uphold the thesis of the "pope can err as a private doctor."

However, this is not what Pius IX and Vatican Council I affirmed.

Pope Pius IX called the First Vatican Council where he was determined to buttress his own spiritual authority. Though many cardinals believed it dangerous to try to define quite how and when the Pope might speak infallibly, a compromise agreement was finally reached.

It stated that Pope "when he speaks ex cathedra, that is when exercising the office of pastor and teacher of all Christians" is "possessed of infallibility" when "he defines... a doctrine concerning faith and morals to be held by the whole Church, through the divine assistance promised to him by St Peter".

Once the Pope has spoken, the First Vatican Council agreed, his definitions "are irreformable of themselves".

However, the Pope does not speak "ex cathedra" on all things every time he speaks. It wasn't until 1950 did the Pope make the first an infallible claim as such. That's right. 80 years went by between Vatican Council I formally recognizing the Pope -could- speak infallibly and the Pope actually doing so. Everything the Popes pronounced between 1870 and 1950 was NOT pronounced "ex cathedra" and therefore infallibly.

That's including everying Pius IX himself said.

This is the error simple-minded peasants like Gesu make. I say, "like" Gesu because he isn't the only peasant on GTV making that mistake. Only when they write of shovelling manure does do they have any real intellectual authority.

Gesu's interpretation, one shared by a number of Spanish-speaking GTV users, is also directly contradicted by the saints and Popes that followed Pius IX.

Pope John Paul II explained the meaning and limits of infallibility in the General Audience of 24 March 1993:

“Infallibility is not given to the Roman Pontiff as a private person, but inasmuch as he fulfils the office of pastor and teacher of all Christians. He also does not exercise it as having authority in himself and by himself, but ‘by his supreme apostolic authority’ and ‘by the divine assistance promised to him in Blessed Peter.’

Finally, he does not possess it as if he could dispose of it or count on it in every circumstance, but only ‘when he speaks from the chair,’ and only in a doctrinal field limited to the truths of faith and morals and those closely connected with them (...) the Pope must act as ‘pastor and doctor of all Christians,’ pronouncing on truths concerning ‘faith and morals,’ in terms which clearly express his intention to define a certain truth and to demand the definitive adherence to it by all Christians.

In July 2005 Pope Benedict XVI stated during an impromptu address to priests in Aosta that: "The Pope is not an oracle; he is infallible in very rare situations, as we know.

Pope John XXIII once remarked: "I am only infallible if I speak infallibly but I shall never do that, so I am not infallible."

Simply put, the Pope isn't infallible every time he opens his mouth. I've already explained this GTV's Latinos and unsurprisingly the result is the same as explaining something to a stubborn Mexican burro.

It just keeps braying the same loud noise.

@Gesù è con noi I am well-versed on the gift of charism of infallibility the LORD endowed his Church with. Not even close to your erroneous understanding here: The apostate Gabriel Barba promotes the LGBT agenda in Argentina with Bergoglio's complicity [where you are having a one-directional “conversation” with yourself], that you are trying to project/force on others.

PS @Ultraviolet And now he has gotten another attack dog @San Atanasio ora pro nobis to do the same here: The First Vatican Council condemned the modernist heresy that the pope can err as a private doctor