We must now consider the power of the ministers of this sacrament, which power depends on the keys. As to this matter, in the first place we shall treat of the keys, secondly, of excommunication, thirdly, of indulgences, since these two things are connected with the power of the keys. The first of these considerations will be fourfold: (1) the nature and meaning of the keys. (2) the use of the keys; (3) the ministers of the keys; (4) those on whom the use of the keys can be exercised.

Under the first head there are three points of inquiry:

(1) Whether there ought to be keys in the Church?

(2) Whether the key is the power of binding and loosing, etc.?

(3) Whether there are two keys or only one?