ubstance of His
blood.

Q. 877. How do we prove the Real Presence, that is, that Our Lord is
really and truly present in the Holy Eucharist?
A. We prove the Real Presence--that is, that Our Lord is really and
truly present in the Holy Eucharist--(1) By showing that it is possible
to change one substance into another; (2) By showing that Christ did
change the substance of bread and wine into the substance of His body
and blood; (3) By showing that He gave this power also to His Apostles
and to the priests of His Church.

Q. 878. How do we know that it is possible to change one substance into
another?
A. We know that it is possible to change one substance into another,
because (1) God changed water into blood during the plagues of Egypt;
(2) Christ changed water into wine at the marriage of Cana; (3) Our own
food is daily changed into the substance of our flesh and blood; and
what God does gradually, He can also do instantly by an act of His will.

Q. 879. Are these changes exactly the same as the changes that take
place in the Holy Eucharist?
A. These changes are not exactly the same as the changes that take place
in the Holy Eucharist, for in these changes the appearance also is
changed, but in the Holy Eucharist only the substance is changed while
the appearance remains the same.

Q. 880. How do we show that Christ did change bread and wine into the
substance of His body and blood?
A. We show that Christ did change bread and wine into the substance of
His body and blood: (1) From the words by which He promised the Holy
Eucharist; (2) From the words by which He instituted the Holy Eucharist;
(3) From the constant use of the Holy Eucharist in the Church since the
time of the Apostles; (4) From the impossibility of denying the Real
Presence in the Holy Eucharist, without likewise denying all that Christ
has taught and done; for we have stronger proofs for the Holy Eucharist
than for any other Christian truth.

Q. 881. {243} Is Jesus Christ whole and entire both under the form of
bread and under the form of wine?
A. Jesus Christ is whole and entire both under the form of bread and
under the form of wine.

Q. 882. How do we know that under the appearance of bread we receive
also Christ's blood; and under the appearance of wine we receive also
Christ's body?
A. We know that under the appearance of bread we receive also Christ's
blood, and under the appearance of wine we receive also Christ's body;
because in the H