On the altar you are looking at the same thing as you saw there last night. You have not heard, however, what this is, what it signifies, or about the greatness of the reality of which it is a sacrament. Your eyes are looking at bread and cup. This is the evidence before your physical sight. But your faith must be instructed concerning it- this bread being Christ 's Body and the cup containing His Blood. Though perhaps these words may be enough to initiate faith, faith must be further instructed in accordance with the Prophet's words: 'Believe that you may understand'
Saint AugustineWicked sons do not have the Holy Ghost in the same way as do beloved sons, and yet they do have Baptism. So, too, heretics do not have the Church as Catholics have, even though they have Baptism.
Saint AugustineBaptism does not profit a man outside unity with the Church ... For many heretics also possess this Sacrament but not the fruits of salvation ... The benefits which flow from Baptism are necessarily fruits which belong to the true Church alone. Children Baptized in other communions cease to be members of the Church when, after reaching the age of reason, they make formal profession of heresy, as, for example, by receiving communion in a non-Catholic Church.
Saint Augustine