Catholic Answers Senior Apologist Jimmy Akin describes the circumstances behind a saint who was also an anti-pope.
Jimmy Akin was born in Texas and grew up nominally Protestant. At age 20 he experienced a profound conversion to Christ. Planning on becoming a Protestant pastor or seminary professor, Jimmy started an intensive study of the Bible, but the more he immersed himself in Scripture, the more he found...
"Deviating from faith, they are implicated in the darkness of perpetual blindness, although they have the day of Christ and the light of the Church before them; while seeing nothing, they open their mouth as if they knew everything, keen for vain things and dull for things eternal."
~ Ambrose, Bishop, Father and Doctor of the Church, Saint; commenting in the 4th century on the "wise of the world" who look askance at Christianity, a conflict that has existed from the very birth of the Faith (see "Science and the Church").