Abstract
This article examines a section of the Roman Catholic rite of the Mass, the offertory, investigating the relationship between theological ideas and the latest reform of liturgical practice (1969). How did the dogmatic theology, developed from the Middle Ages until the age of the Protestant Reformation, influence the liturgical reform under Paul VI? This is taken as a case to thematise the interplay between theological datum (lex credendi) and practical datum (lex orandi).