In the first volume on the Sacraments St. Robert follows the order of teaching in the Council of Trent to defend Catholic truth against the teaching of early Protestants. In his work On the Sacraments in General He defends the Catholic notion of Sacraments as well as their use. He looks to the definition of a Sacrament and then the matter and form the author of the Sacraments the difference between the Sacraments used in the Old Testament and in the New whether one can change the matter and form