The natural follow-up question is: was the Syllabus ever retracted/affirmed?
It was never formally retracted. But
Vatican II's Dignitatis Humanae (1965) declared that the human person has a right to religious freedom, affirming as a civil right exactly what the Syllabus condemned as an error. Rome's official position is that this is not a contradiction but a "development of doctrine." (Thanks John Henry Newman) The problem is that both traditionalist Catholic scholars and progressive Catholic scholars agree it IS a reversal, but they disagree if it is good or bad.
This creates an inescapable ?trilemma? Rome cannot escape from:
Option 1: The Syllabus was correct --> Vatican II's Dignitatis Humanae is heresy --> the post-Vatican II Church is in error. This is the position of the SSPX, whose founder Archbishop Lefebvre pointed out that accepting Vatican II requires believing that "for two millennia, popes, saints, Fathers and Doctors of the Church, bishops, and Catholic kings constantly violated the natural rights of men without anyone in the Church noticing." (
source)
Option 2: Dignitatis Humanae is correct --> the Syllabus was wrong --> a pope formally taught error in a solemn magisterial document --> the entire magisterial system's credibility collapses.
Option 3: Rome's "hermeneutic of continuity" is correct and there's no real contradiction --> you must believe something that both traditionalist and progressive Catholic scholars reject as logically strained.
Pick your poison. Catholics go to hell anyways. Under Sola Scriptura this problem never would have existed, because the Word of God would have been the fixed standard throughout and not an accumulating pile of contradicting papal documents.