Most Holy Trinity Seminary

Most Holy Trinity Seminary is a seminary founded in 1995 by Donald Sanborn. Sanborn is a bishop known for advocating sedeprivationism, the "Cassiciacum thesis" within the wider sedevacantist milieu. He is the seminary's rector and also leads the Roman Catholic Institute as superior general (Wikipedia).

Locations. Accounts differ on where the seminary began. In August 2003 the Tampa Bay Times reported that Hernando County planners had voted 4–1 to allow a small seminary on 50 acres. According to the report, Sanborn wanted to move the seminary there from the Detroit suburbs, expected it to train about 18 to 20 priests, and said it would not be affiliated with the local Catholic diocese or parishes. The seminary later operated in Brooksville, Florida, and moved to Reading, Pennsylvania, in fall 2022 (Wikipedia). A U.S. Department of Homeland Security listing of certified schools gives a Reading address (Study in the States).

Positions. Sedeprivationism holds that the post-conciliar popes were validly designated but hold the papacy only "materially," lacking authority unless they withdraw the changes of Vatican II (Wikipedia: Sedeprivationism). The seminary's bishops were consecrated without a papal mandate. Sanborn was consecrated in 2002 by Robert McKenna, who had himself been consecrated by the thesis's author, Michel-Louis Guérard des Lauriers.

Church teaching on the point at issue. The Second Vatican Council teaches that the Roman Pontiff, as Peter's successor, is the perpetual and visible source and foundation of the unity of bishops and faithful (LG 23) (Lumen Gentium).