St. Thomas Aquinas (c. 1225-1274) is considered to be the greatest theologian of the high Middle Ages. He wrote so many volumes that no one could begin to condense his writings in a single blog entry, but his Eucharistic theology is distilled in some hymns, one of which I especially like to sing during Holy Week:
Now, my tongue, the mystery telling
of the glorious Body sing,
and the Blood, all price excelling,
which the Gentiles' Lord and King,
once on earth among us dwelling,
shed for this world's ransoming.
Given for us, and condescending
to be born for us below,
he with us in converse blending
dwelt, the seed of truth to sow,
till he closed with wondrous ending
his most patient life of woe.
That last night at supper lying
mid the twelve, his chosen band,
Jesus with the law complying,
keeps the feast its rites demand;
then, more precious food supplying,
gives himself with his own hand.
Word made flesh, the bread he taketh,
by this word his Flesh to be;
wine his sacred Blood he maketh,
though the senses fail to see;
faith alone the true heart waketh
to behold the mystery.
Therefore we, before him bending,
this great Sacrament revere;
types and shadows have their ending,
for the newer rite is here;
faith, our outward sense befriending,
makes our inward vision clear.
Glory let us give and blessing
to the Father and the Son,
honor, thanks, and praise addressing,
while eternal ages run;
ever too his love confessing
who from both with both is One.