Chapter 15 — Part II: The Sacraments — Introduction on the Sacraments in General
Section 19. In order, therefore, to explain more fully the nature of a Sacrament, it should be taught that it is a sensible object which possesses, by divine institution, the power not only of signifying, but also of accomplishing holiness and righteousness. Hence it follows, as everyone can easily see, that the images of the Saints, crosses and the like, although signs of sacred things, cannot be called Sacraments. That such is the nature of a Sacrament is easily proved by the example of all the Sacraments, if we apply to the others what has been already said of Baptism; namely, that the solemn ablution of the body not only signifies, but has power to effect a sacred thing which is wrought interiorly by the operation of the Holy Ghost.