[At Vatican I fides et mores were key terms, ordinarily translated as “faith and morals” and understood as separable terms. Were they always so distinguished? Did mores traditionally mean “morals”? Piet Fransen traced their origin to a letter of St. Augustine and followed their use through the Middle Ages to the Council of Trent. Afterwards, the meaning of mores changed from ecclesiastical customs to morals; fides became a concept rather than the lived faith of the Church.]