salvation of God": and this is taken for the most part from the
Psalms, or, at least, is sung with a Psalm, because, as Dionysius
says (Eccl. Hier. iii): "The Psalms comprise by way of praise
whatever is contained in Sacred Scripture."

The second part contains a reference to our present misery, by reason
of which we pray for mercy, saying: "Lord, have mercy on us," thrice
for the Person of the Father, and "Christ, have mercy on us," thrice
for the Person of the Son, and "Lord, have mercy on us," thrice for
the Person of the Holy Ghost; against the threefold misery of
ignorance, sin, and punishment; or else to express the
"circuminsession" of all the Divine Persons.

The third part commemorates the heavenly glory, to the possession of
which, after this life of misery, we are tending, in the words,
"Glory be to God on high," which are sung on festival days, on which
the heavenly glory is commemorated, but are omitted in those
sorrowful offices which commemorate our unhappy state.

The fourth part contains the prayer which the priest makes for the
people, that they may be made worthy of such great mysteries.

There precedes, in the second place, the instruction of the faithful,
because this sacrament is "a mystery of faith," as stated above (Q.
78, A. 3, ad 5). Now this instruction is given "dispositively," when
the Lectors and Sub-deacons read aloud in the church the teachings of
the prophets and apostles: after this "lesson," the choir sing the
"Gradual," which signifies progress in life; then the "Alleluia" is
intoned, and this denotes spiritual joy; or in mournful offices the
"Tract", expressive of spiritual sighing; for all these things ought
to result from the aforesaid teaching. But the people are instructed
"perfectly" by Christ's teaching contained in the Gospel, which is
read by the higher ministers, that is, by the Deacons. And because we
believe Christ as the Divine truth, according to John 8:46, "If I
tell you the truth, why do you not believe Me?" after the Gospel has
been read, the "Creed" is sung in which the people show that they
assent by faith to Christ's doctrine. And it is sung on those
festivals of which mention is made therein, as on the festivals of
Christ, of the Blessed Virgin, and of the apostles, who laid the
foundations of this faith, and on other such days.

So then, after the people have been prepared and instructed, the next
step is to proceed to the celebration of the mystery, which