"But what is Tradition? It seems to me that the word is often imperfectly understood. It is equated to the “traditions” that exist in trades, in families and in civic life: the “bouquet” fixed to the roof of a house when the last tile is laid, the ribbon that is cut to open a monument, etc. That is not what I am referring to: Tradition does not consist of the customs inherited from the past and preserved out of loyalty to the past even where there are no clear reasons for them. Tradition is defined as the Deposit of Faith transmitted by the Magisterium down through the centuries. This deposit is what has been given to us by Revelation; that is to say, the Word of God entrusted to the Apostles and transmitted unfailingly by their successors.
But now they want to get everyone inquiring, searching, as if we had not been given the Creed, or as if Our Lord had not come to bring us the Truth once and for all. What do they claim to discover with all this inquiry? Catholics upon whom they would impose these “questionings,” after having made them “abandon their certainties,” should remember this: the deposit of Revelation concluded at the death of the last Apostle. It is finished and it cannot be touched until the end of time. Revelation is irreformable. The First Vatican Council re-stated this explicitly: “for the doctrine of faith which God has revealed has not been proposed, like a philosophical invention, to be perfected by human ingenuity; but has been delivered as a divine deposit to the Spouse of Christ (the Church) to be faithfully kept and infallibly declared.""
-Archbishop Marcel Lefebvre, Open Letter to Confused Catholics