§1381
Sacraments › … › V. The Sacramental Sacrifice Thanksgiving, Memorial, Presence
The presence of Christ by the power of his word and the Holy Spirit
"That in this sacrament are the true Body of Christ and his true Blood is something that 'cannot be apprehended by the senses,' says St. Thomas, 'but only by faith, which relies on divine authority.' For this reason, in a commentary on Luke 22:19 ('This is my body which is given for you.'), St. Cyril says: 'Do not doubt whether this is true, but rather receive the words of the Savior in faith, for since he is the truth, he cannot lie.'"
Godhead here in hiding, whom I do adore
Masked by these bare shadows, shape and nothing more,
See, Lord, at thy service low lies here a heart
Lost, all lost in wonder at the God thou art.
Seeing, touching, tasting are in thee deceived;
How says trusty hearing? that shall be believed;
What God's Son has told me, take for truth I do;
Truth himself speaks truly or there's nothing true.
Source: Catechism of the Catholic Church (Vatican.va)