Yet the dogma of papal infallibility was not formally defined until the First Vatican Council (1869-1870) – i.e. "When, in the exercise of his office as shepherd and teacher of all Christians, in virtue of his supreme apostolic authority, (the Bishop of Rome) defines a doctrine concerning faith or morals to be held by the whole Church."
Just as a word is added to the dictionary only after it is already in common use, a dogmatic definition is rendered only regarding a matter of Faith or morals that has been in place for 2,000 years. The definition comes after; the thing itself already exists and is not made by the definition.
Thus it is incorrect to say that the dogma of papal infallibility did not exist until the late 19th century. Rather, it existed from the time of Christ and the apostles, and it merely received its solemn definition in the late 19th century.
Thus, too, it is incorrect to say that all that the Pope says is infallible, or presumed to be infallible. The Pope’s pronouncements must be in accord with what has been universally believed and practiced by Christians for 2,000 years.