How did the Church develop its teaching on infallibility? When was this teaching declared? Who was the first pope to infallibly define infallibility?
The teaching was dogmatically defined in the First Vatican Council (1869-1870).
It was during the pontificate of Pope Pius 9th.
However, this was the belief of the church for quite some time before that (I’m talking centuries).
The Wikipedia article on the subject is actually rather well done (although it gives, in my opinion, too much space to possible objections to the dogma—some of which are rather far-fetched or poorly reasoned).
We might note that the Second Vatican Council refined the teaching on infallibility, to express how the College of Bishops, in union with its head, the Pope, is also a subject of infallibility, both in ordinary and in extraordinary ways. This is laid out in Lumen Gentium chapter 3, especially LG 25.
As a suggestion, read the document provided in the link from Vat I for an explanation to your question
Shouldn’t a Pope have defined that, not a council? How can a council infallibly teach that a council has infallible authority. That doesn’t make sense
Shouldn’t a Pope have defined that, not a council? How can a council infallibly teach that a council has infallible authority. That doesn’t make sense.
How naïve, and out of touch with Catholic teaching which is explained in the CCC, as Ecumenical Councils are called to enable contributions from the cardinals and bishops and the proposals have to be approved by the Pope to be legitimate.
Gallicanism became Conciliarism after the Great Western Schism, claiming the superiority of council over the Pope, and promoted by John Gerson (1363-1429) and Peter d’Ailly (1350-1420). The French Revolution drove the bishops into the arms of the Pope and dealt a mortal blow to Gallicanism, but the basic idea was still alive until the First Vatican Council formally condemned it in 1870.
CONCILIARISM. The theory that a general council of the Church is higher in authority than the Pope. It began in the fourteenth century, when respect for the papacy was undermined by confusion in Church and State. William of Ockham (1280-1349), in his battle with Pope John XXII (c. 1249-1334), questioned the divine institution of the primacy. Marsilius of Padua (1324) and John Jandun (1324) declared it was only a primacy of honor. During the great Western Schism (1378-1417) many otherwise reputable theologians, such as Peter of Ailly (1394) and John Gerson (1409) saw in the doctrine of the council’s superiority over the Pope the only means of once more reuniting a divided Church. The viewpoint appeared that the Church in general was free from error, but the Church of Rome could err, and in fact had erred and fallen into heresy. The Council of Constance (1414-18), in its fourth and fifth sessions, declared for the superiority of council over Pope. However, these decisions never received papal approbation. In Gallicanism the conciliarist theory lived on for hundreds of years. Conciliarism was formally condemned by the First Vatican Council (1869-70), which defined papal primacy, declaring that the Pope had “full and supreme jurisdiction over the universal Church, not only in things which belong to faith and morals, but also in those which relate to the discipline and government of the Church spread throughout the world.” He therefore possesses not merely the principal part but “all the fullness of this supreme power.” Moreover, this power is ordinary or constant, and immediate or direct; it extends the Pope’s authority over each and all the churches, whether local or territorial, and over each and all the churches, whether local or territorial, and over each and all the pastors and the faithful (Denzinger, 3063).
In more recent times, conciliarism has been renewed by those who appeal to a “magisterium of theologians” or “consensus of the people of God” against ordinary or even solemn teachings of the popes. (Etym. Latin concilium, council, assembly for consultation.)
Modern Catholic Dictionary by Fr. John A. Hardon, S.J.
The doctrine of Papal infallibility is found in Scripture (Mt 16:17-19; Jn 21: 15-17; Mt 28:19-20; 1 Tim 3:15), and for the final proposed definition of Vatican I there were 471 bishops for and 130 against; more than two-thirds bishops for. Sixty-six bishops then returned to their dioceses before the Public Session, but all eventually declared full acceptance of the defined doctrine. [Dr Leslie Rumble, *Questions People Ask, Chevalier, 1975, p 159].
It was actually determined at the first council of Jerusalem around A.D. 50.
To expand a little on the original question. What is the understanding of how a pope is preserved from the possibility of teaching error in the exercise of his office?
The pope is prevented by the Holy Spirit from teaching heresy under the conditions that fit the criteria for infallibility.
The pope ceases to be the pope when he teaches heresy under the conditions that fit the criteria for infallibility.
Obviously the first
Let’s take the two examples of the Immaculate Conception and the Assumption. Is it clear that these were intended for the whole world, and not just the Latin Rite?
How would it even be possible to make the teaching of an objective fact (that Our Lady was preserved from original sin or assumed bodily into heaven) binding only on some Catholics? “This is a thing that God truly did, but it’s only true for some of us”?
Church practices (specific liturgical rites or rules of fasting, say) can be binding only on certain Catholics, but when the declaration is “this thing is true and really happened,” that approach doesn’t even make sense.
….the Immaculate Conception and the Assumption. Is it clear that these were intended for the whole world, and not just the Latin Rite?
Both of these are dogmas. Never ever are dogmas or doctrines other than for the whole world.