As such, it could come as a surprise to many Catholics to learn that Leo XIV and his Vatican actually reject certain key portions of Vatican II that the SSPX accepts. The analysis that follows looks at two of the most important concepts in the Church today — doctrinal development and ecumenism — to demonstrate that Vatican II condemns Leo’s Vatican, not the SSPX. The only way that can proceed, then, is by rejecting this all-important guardrail of Vatican II. False ecumenismMost Catholics with some familiarity with Vatican II may believe that it unambiguously supports the false ecumenism that we see today. So if we look at the greatest problems in the Church today, they relate directly to Rome’s refusal to follow the explicit teachings of Vatican II.