Complex sentence: After his conversion back to Roman Catholicism Sungenis became known as a radical Traditionalist Catholic and wrote a book of apologetics, explaining his view of the Catholic Church's doctrine of justification and his critique of the Protestant doctrine of salvation by faith alone.
Split into simpler sentences: After his conversion back to Roman Catholicism Sungenis became known as a radical Traditionalist Catholic. He wrote a book of apologetics, explaining his view of the Catholic Church's doctrine of justification and his critique of the Protestant doctrine of salvation by faith alone.