Question: "What is sedevacantism?"
Answer: Sedevacantism is the belief that the Roman Catholic Church currently lacks a valid Pope. It implies that whoever currently holds the office does so in name only. The Pope may have been elected and accepted by cardinals yet, due to heretical views, is not “truly” the head of the earthly church. The terms sedevacantist and sedevacantism come from a Latin phrase that means “the chair is empty.” Those taking this view consider themselves Catholic yet believe the current Pope espouses heresy, which disqualifies him from office. Most sedevacantists believe the papacy has been vacant since modernist reforms were passed in the 1960s.
The most-often accepted Catholic interpretation of Matthew 16:18 implies there will always be a Pope. This stance claims the only gaps are between the end of one Pope’s service and the election of the next, with no true absences. Despite history’s record of serious flaws and scandals in the Vatican, mainstream Catholicism does not believe any Pope has been truly “invalid.”
Sedevacantists argue that any Pope who espouses heresy invalidates his role. The Catholic concept of papal infallibility only applies to statements the Pope makes officially, in concert with the cardinals. It does not suggest that Popes are entirely inerrant or sinless. However, sedevacantists argue that actual heresy disqualifies priests, bishops, and cardinals from office. A heretical official, by that logic, cannot be Pope; therefore, any such person has no valid claim to the office.
In politics, the boundaries between “disagreeable” and “unconstitutional” often shift based on partisan bias. In kind, arguments over sedevacantism are usually proxy battles for other doctrinal disputes within Roman Catholicism. The main body of such debates involves modernism and ecumenism.
Most sedevacantists are from the United States, via the current “movement” of sedevacantism that began in the mid-1960s. The chief complaint of this group concerns reforms passed during the Second Vatican Council. According to sedevacantists, those changes are heretical. Therefore, anyone who agrees with the Second Vatican Council is not a valid priest, and, therefore, every Pope who has been elected since that council is invalid, leaving the Catholic Church technically without a Pontiff since then.
Within Catholicism sedevacantists are the overwhelming minority. There are arguments both for and against sedevacantism; however, the nature of those arguments reveals the theological problems inherent in Roman Catholicism. The institution’s extreme dependence on fallible people—or even on a single fallible person—is hard to square with the Bible’s frequent depiction of a unified, equal, worldwide church (1 Corinthians 1:12–17; Luke 20:46; Revelation 1:4–6).