During the First Vatican Council, the most common objection against the definition of papal infallibility was that if it is so defined, there would no longer be a need for an ecumenical council. Bishop Gasser in his relatio on the definition answered this objection. Here is Fr. James T. O'Conner's take on his answer in his commentary on the relatio:
"Living as we do after the celebration of a Second Vatican Council, the objection seems to carry little weight, and, indeed, history has demonstrated that Gasser's reply was accurate. He said, in essence: papal infallibility is not a new doctrine; the Pope has always been infallible. We are simply about to define that truth. And, although, the Pope has always been infallible, ecumenical councils were held in the past and so will they be in the future. They have never been, he says, absolutely necessary, but they have always been the 'most solemn judgment' of the Church in matters of faith and morals, since they visibly manifest the union of the Pope with the other bishops in fulfilling their roles as teachers of the faith. As such, ecumenical councils will always remain necessary."
Gasser's relatio can be found in the book "The Gift of Infallibility" along with Fr. O'Conner's theological synthesis of papal infallibility. This is an excellent book! If anyone is struggling with the Dogma of Papal Infallibility, (whether Catholic, Orthodox, or Protestant) they should get* this book as soon as possible. You might come away with a different view and you will definitely understand the dogma better!
*I just did a search for this on amazon in order to link to it and apparently it is out of print and not available for less than $90 (which I assure my wife is not the price I paid for it!). I'm sure your local library will have a copy though, so go get it!