"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'"

Source: Augustine Saint Bishop of Hippo, St Augustine (2008). “The Happy Life; Answer to Skeptics; Divine Providence and the Problem of Evil; Soliloquies (The Fathers of the Church, Volume 5)”, p.59, CUA Press