That is a completely circular, anachronistic interpretation of history using hindsight to impose a modern definition that was unknown in Honorious' day on that era. It must be a nice gig, if you can get it, to able to overturn the facts of history by mere dogmatic authority.
Actually, what you end up with that kind of circular reasoning is a concept that means nothing at all because you can never know if a current Pope's teaching will be approved by future generations, or will end up as one of those "he didn't mean that infallibly" pronouncements.
And btw, where did you come up with the "previously established infallible teaching" part of the definition of ex cathedra?
Ex CathedraLiterally "from the chair", a theological term which signifies authoritative teaching and is more particularly applied to the definitions given by the Roman pontiff. Originally the name of the seat occupied by a professor or a bishop, cathedra was used later on to denote the magisterium, or teaching authority. The phrase ex cathedra occurs in the writings of the medieval theologians, and more frequently in the discussions which arose after the Reformation in regard to the papal prerogatives. But its present meaning was formally determined by the Vatican Council, Sess. IV, Const. de Ecclesiâ Christi, c. iv: "We teach and define that it is a dogma Divinely revealed that the Roman pontiff when he speaks ex cathedra, that is when in discharge of the office of pastor and doctor of all Christians, by virtue of his supreme Apostolic authority, he defines a doctrine regarding faith or morals to be held by the universal Church, by the Divine assistance promised to him in Blessed Peter, is possessed of that infallibility with which the Divine Redeemer willed that his Church should be endowed in defining doctrine regarding faith or morals, and that therefore such definitions of the Roman pontiff are of themselves and not from the consent of the Church irreformable." (See INFALLIBILITY; POPE.)
New Advent Catholic Encyclopedia
Cordially,
The reasoning on infallibility is not circular. Any teaching from a pope that conflicts with previous infallible teaching is immediately null and void.
If there is some powerful interest supporting the error, it may temporarily gain currency. However, any Catholic who detects heresy from ANY source is obligated to resist it.
The basis of Church doctrine was established long ago so the occasions for new infallible teachings are very infrequent. A new teaching cannot be valid if it conflicts with any previous infallible teaching. That would require the old teaching that was once true to become false. Obviously, such a transformation is impossible, even for a pope. Do you understand how this logic is linear and not at all circular?