In
the New Testament, we read in Revelation 3[:7], “He who has the key of David
opens and no one shall shut, shuts and no one shall open.” It is no objection that
the text of the Gospel does not say that if Peter opens none shall shut and if
he shuts none shall open. Though these words do not occur, the meaning is
there. For the Gospel does refer to the lesser actions included in the power of
the keys: “Whatever you bind on earth shall be bound in heaven, and whatever
you loose on earth shall be loosed in heaven” [Matthew 16:19]. Obviously, this
means that what Peter binds no one losses and what he looses no one binds. For
what is bound on earth is also bound in heaven, that is, it is so bound that no
one shall loose. Similarly, what is loosed on earth is also loosed in heaven,
that is, it is so loosed that no one shall bind.
This
suffices to show that Peter opens the kingdom of heaven in such a way that no
one shall shut, and so shuts that no one shall open. For it follows that the
keys given Peter will carry out their proper actions in a higher and not a
lower manner that holds for the lower actions. Note also that the words of
Isaiah 22 speak of Eliakim with reference to Christ, as the gloss on this verse
says. (“the key carried on his shoulder can be understood as the scepter of the
kingdom and the trophy of victory, that is, as the cross Christ carried on his
own shoulder.” Glossa Ordinaria, on Isaiah 22:23 [PL 113, 1265]) As a
further sign of this John the Evangelist repeats the same thing about Christ [Revelation
3:7], so as to show he was prefigured in Eliakim. Isaiah himself wrote of
Christ in 9[:6], “And the rule will be upon his shoulder,” to show that the key
on his shoulder is the rule on his shoulder. Hence we also understand that “the
keys of the kingdom of heaven” refers to the fulness o authority. In addition
to these testimonies there is the custom that the keys of the realm are
presented to a king as a sign of his supreme authority.
If
we link together the two promises, it becomes evident that in these words Peter
was promised the pontifical office over the Catholic Church. From the first
promise, Peter is to be the foundation of the Catholic Church. This promise
establishes Peter’s office of supporting the Catholic Church in firmness of
faith and at the same time imposes on the Catholic Church the necessity of adhering
to Peter its foundation. If a building is to be built up, it must necessarily
adhere to the rock on which it is founded. In the second promise, the fulness
of authority in the Church is promised Peter. Clearly these two are the
principal elements in the pontifical office over the whole Christian Church. (Tommaso
De Vio Cajetan, “The Divine Institution of the Pontifical Office Over the Whole
Church in the Person of the Apostle Peter [February 18] 1521,” in Cajetan
Responds: A Reader in Reformation Controversy [trans. Jared Wicks;
Washington, D.C. : The Catholic University of America Press, 1978; repr., Eugene,
Oreg.: Wipf and Stock, 2011], 115-16)