Chapter 15 — Part II: The Sacraments — Introduction on the Sacraments in General
Section 34. Constituent Parts of the Sacraments — In the first place, then, it should be explained that the sensible thing which enters into the definition of a Sacrament as already given, although constituting but one sign, is twofold. Every Sacrament consists of two things, matter, which is called the element, and form, which is commonly called the word.