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...
"For the Scripture says 'Holy, holy, holy Lord of hosts; full is every creature of his glory'. And we, led by conscience, gathered together in one place in concord, cry to Him continuously as from one mouth, that we may become sharers in His great and glorious promises."
~ The Sanctus, here described by Pope Clement I (from his I Cor., 34:6-7) circa A.D. 95, is one of the most ancient parts of the sacred liturgy, tracing back to the time of the apostles.