Allegedly, Bl. Pope Pius IX said “Tradition? I am tradition!” when confronted with an argument against papal infallibility at the First Vatican Council.
The misquotation originates from an 1870 book called Letters from Rome on the Council that claims to preserve the letters of three people who informally met various persons who were present at the First Vatican Council. The preface of the book sets itself up as offering “the most serviceable weapons for combating the legitimacy of the Council” and its audience is “Liberal Catholic[s].” (Preface Page VII) Among those letters is Letter 61, on pages 712-731, which reports that the pope said the words “La tradizione son’ io,” which means “I am tradition,” to a cardinal who objected to papal infallibility.
The specific letter that these words appear in argues that the pope himself might have started the chain of gossip that produced these words: “The following account of the dialogue between the Pope and the Cardinal is current at Rome, and it seems to rest on…Pius himself, who is notoriously fond of telling every one he meets how he lectured this or that dignitary.” Then follows the account with the words “La tradizione son’ io.”
Note well: does the book claim to report the direct words of the pope? No, the preface says it contains only a bunch of letters from other people who happened to be in Rome at the time, and this specific letter merely conjectures that the pope might have said these words. Does it report the direct words of people who talked with the pope? No, it says this dialog comes from gossip circulating in Rome, or rather one particular version of the gossip written by “Liberal Catholic[s]” interested in “combating the legitimacy of the Council.”
Do these letters report formal interviews with the people who met the pope? No. Do they report impressions made on third-party people based on informal talks with those people? They claim to, and such impressions are problematic as a historical source. But the book doesn’t even claim to report those informal impressions accurately. It says, “[The original] letters were addressed to a friend in Germany, who added now and then historical explanations to elucidate the course of events, and then forwarded them to [someone else].” (Preface Page V)
Based on the preface and the introduction to Letter 61, this supposed quote from the pope is unreliable. It is information handed down informally through at least eight different parties, some of which added things, some of which was pure gossip, and some of which was written with the specific intention of making the Council and its pope look bad. Allegedly, the pope (the first party) said “I am tradition” to a cardinal (the second party), someone at the council found out about it somehow (the third party), then it became gossip (the fourth party), this gossip was informally mentioned in conversation to a letter writer (the fifth party), he forwarded an informal writing about it to an anonymous guy in Germany (the sixth party), he added some things, then forwarded it to someone else (the seventh party), and they finally made it to the compiler of this book (the eighth party), who, by the way, uses the pseudonym Quirinus and not his real name, which is unknown.
The letter is gossip handed down through at least eight questionable sources. It should not be regarded as historical or a real quote from the pope. Rather, it is simply a “pope fiction!”