two instances of infallibility?

[dairygirl4u2c]

why is there a commonly understood teaching that the pope has only taught from his Chair twice? 

there is an important article on this by famed catholic apologist jimmy akin.
http://jimmyakin.com/2004/06/two_instances_o.html

any time the pope "defines" a doctrine it is infallible according to vatican I. or as i like to say the pope, binds, the church, on faith and morals... the definition of infallibility. 

this has been explicitly done many times in the past "We define... xyz" such as the teaching that there is no salvation outside the catholic church, just as an example. 

ive seen that "two times" idea repeated here, and even heard it from a bishop who is said to have studied infallibility in rome. 

why does that idea even persist? where if at all is the truth to it?  has there only been two instances of "this is infallible and i declare it so based on my prerogatives as an infallible teacher"?

[little2add]

Throughout the Old Testament there have been many laws laid down by the Lord, that are perhaps more harsh then we, as Christians, follow today. Many times in the New Testament it has been found to change the laws of the Old Testament. My question is does the New Testament override the Old Testament in creating laws, that we as Christians should follow.
Old Testament: Exodus 21:24
eye for eye, tooth for tooth, hand for hand, foot for foot,
Then later in the New Testament: Matthew 5:38-48
38 “You have heard that it was said, ‘Eye for eye, and tooth for tooth.’ 39 But I tell you, do not resist an evil person. If anyone slaps you on the right cheek, turn to them the other cheek also. 40 And if anyone wants to sue you and take your shirt, hand over your coat as well. 41 If anyone forces you to go one mile, go with them two miles. 42 Give to the one who asks you, and do not turn away from the one who wants to borrow from 

You can find your answer a few verses earlier in the same chapter:
Matthew 5:17-18

17 Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfill.
18 For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled.
The Law of Moses was given to point people's minds forward to Jesus Christ, the promised Messiah-to-come. Once he did come, the Law's purpose was fulfilled, and it became obsolete. It was not destroyed, but superseded by a higher law, the law of the Gospel.

[MarysLittleFlower]

Its funny I JUST came from a catechism class where this was addressed. If I understand correctly, there are numerous things that are infallible - which books are in Scripture, doctrines, Councils statements etc and all these things were accepted by the Pope. If a future Pope teaches them again like references them that is infallible. However explicitly making an ex cathedra statement and defining something doesn't happen as often . So it seems that there were 2 ex cathedra statements, but they don't exclude other cases of infallibility - there just wasn't a need to define them again after a Council worked them out. Things are typically defined when there is confusion or opposition on the topic. A Pope today doesn't maybe have a pressing need to define a topic that was discussed in detail in an early Church Council. A Pope was at the council and approved it, and the doctrines are infallible, but we don't need a formal ex cathedra statement like we did for the Immaculate Conception. The Immaculate Conception was debated about at the time so the Pope defined it.  Mostly they don't define things ex cathedra and rather repeat things that there's no controversy over. Doctrines are infallible because of the Pope but they only become dogmas proclaimed ex cathedra when there's a need. At least that is my understanding! People who talk about the two statements are referring to those ex cathedra dogmas. Its true there aren't many of those.