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.
So then, should anyone, which God forbid, have the temerity to reject this definition of ours: let him be anathema.
By this document in 1870 the Roman Catholic Church formally affirmed what it had informally embraced long beforehand: the belief that the Pope, when he speaks ex cathedra (literally, "from the chair"), speaks infallibly. This doctrine was not received universally even among self-identified Roman Catholics (e.g., Hans Küng). Of course, Dissenters have rejected the notion of papal infallibility for as long as there have been Dissenters. To be a Dissenter is, ipso facto, to reject papal infallibility. Martin Luther warned of Roman Catholic apologists who "with insolent juggling of words…would persuade us that the pope, whether he be a bad man or a good man, cannot err in matters of faith," in his "Open Letter to the Christian Nobility of the German Nation Concerning the Reform of the Christian Estate."
Asserting infallibility for one's leaders initially seems to be a strong position from which to lead. It stifles dissent, and dissent is rarely productive or efficient while it is actually ongoing. But in the long run, infallibility cripples leadership rather than enabling it. Among the most necessary tasks of leadership is the recognition of past mistakes and their correction. One could adopt the Mormon solution and just presume that nobody is paying close attention—Mormons have an office of living prophet, supposedly delivering authoritative revelations from God, which subsequent prophets then contradict or rescind entirely. If Harold Camping can get away with what he's done, what, in comparison, is a little difference of opinion over whether the moon is inhabited by Quakers?
But the Roman Catholic Church is too large, too well organized, and too closely watched to get away with such tactics. Modern-day popes and priests have to make certain that their teachings comply with former ex cathedra teachings. Therefore, there is no hope for Roman Catholics to correct their errors regarding such things as the immaculate conception or the bodily assumption of Mary unless they correct the error of having embraced papal infallibility first. Even if they come to be 100% aware of having departed from the truth in these matters, they cannot fix what is broken so long as Vatican I's error on papal infallibility shackles them to an errant past.
And yet, harmful as the doctrine of papal infallibility may be, it has done far less danger in recent years than the even more ludicrous notion of judicial infallibility, styled under the name of stare decisis or "precedent." Because of the notion of stare decisis, our court system struggles to right itself when it makes grievous errors.
Of course, judges and legal theorists are like neither Roman Catholics nor Mormons. They do not believe that judges are actually infallible, guided by God in all of their decisions to perfect and timeless wisdom. They know that judicial decisions are often wrong, and occasionally they find a way to reverse themselves. An interesting paper available on the Internet details some of the situations in which the United States Supreme Court has abandoned stare decisis and has overruled its own rulings (see here).
Reversals of "settled law" are, nonetheless, rare. Even the most strident originalists (like Clarence Thomas, maybe…contrast Scalia's characterization of Thomas with Thomas's rejoinder) often assert that legal decisions ought not to be overturned merely because they are wrong. Thoughtful discussions of the doctrine of stare decisis usually quote at some time Justice Brandeis's 1932 dissent in Burnet v. Coronodo Oil & Gas, which reveals poignantly the flawed theory behind stare decisis:
Stare decisis is usually the wise policy, because in most matters it is more important that the applicable rule of law be settled than that it be settled right…This is commonly true even where the error is a matter of serious concern.
So, the regnant philosophy of our judicial system is that it is better to be consistently wrong than to be inconsistent in order to be right. The structure of our judicial system is designed in opposition toward one of the most fundamental (and most demonstrably true) tenets of Christianity: The fact that men err and must often repent of their errors.
Consider, as foremost example, the 1973 case Roe v. Wade. When you hear a Supreme Court nominee answering any question about stare decisis, you can just substitute "Roe v. Wade" for "stare decisis" to get the true intent of the question. The pro-abortion crowd do not want to have the debate about whether Roe was right constitutionally or morally; they just want to have a debate over whether it is "settled." For those who think like Brandeis, the important thing is that cases like this one be "settled" even if they are not "settled right."
I believe that there are at least two flaws in Brandeis's thinking.
Brandeis overestimates the degree to which judicial "settling" accomplishes societal "settling."
If anything, the Roe v Wade decision has accomplished a massive unsettling of American society. Most of the presidential elections since 1980 have turned to some degree upon the unsettling and polarization of American society that Roe caused. When a court makes a political ruling, usurping the legislative function along the way, and then tries to lock in its gains by appeal to stare decisis, the result is to undermine public confidence in the justice system and to unsettle society.
What is soothing to society is a feeling of trust that those who wield the power of government are committed to doing the right thing, even if doing so should require enduring the embarrassment of correcting one's past mistakes or might inconvenience one's political agenda.
"Settled" is more important than "settled right" to whom?
Certainly, the victim is more concerned about a ruling being right than being settled. The cause of justice is served better by right decisions than by mere stability. When "settled" is not "settled right," then it is nothing more nor less than obstinacy. Obstinacy in rulers is a key ingredient in the fomenting of rebellion.
This kind of obstinacy is recognized as poor leadership in every area of human endeavor except jurisprudence. When leaders don't have to revisit their decisions, they feel peace. When those who suffer under bad decisions have no hope that their leaders will revisit their mistakes, they feel at least despair, sometimes anger, and occasionally determination to effect change.
Whether in matters of faith or in matters of law, irreversible rulings are incompatible with liberty. Unless the one delivering the rulings is indeed infallible, irreversible rulings are also contrary to justice and progress. Whether it is the chair of St. Peter or the bench of John Jay, the fallen and fallible human souls who sit in them ought to have enough humility to realize that sometimes they need to be corrected.