Question Two of Chapter Four of the Second Decade
That one or several angels can be assigned to the guardianship of human beings
It is asked whether one or several angels are assigned to each individual human being for guardianship.
To this it is answered that an angel is given to each individual human being for guardianship, because, since the guardianship of angels is for obtaining advancement toward the end and for removing those things which impede the attainment of the end, the guardianship of angels is therefore owed to all those who have not yet attained their final end. All human wayfarers are of this sort.
And if it should be said, as the Master of the Sentences says in Book II, distinction 11: How is it possible for an angel to be deputed to every rational soul, when past, present, and future souls are more numerous than the angels deputed to guardianship?
The Master answers there that at no time are there as many human beings simultaneously existing in actuality as there are good angels. Therefore, one of the angels for each human being is sufficient. For when one human being dies, the angel given to his guardianship is assigned to another who succeeds him.
And although, as Thomas says in the First Part, question 113, article 2, one angel is deputed to each human being insofar as each is a particular person, it is nevertheless not unfitting that several angels be deputed to some human being according to the dignity of his prelacy and some grace of God participated by him, as is evident in the Supreme Pontiff, in cardinals possessing the key of jurisdiction, in prelates, and in princes.
All these things are from Thomas in the First Part, and from the theological doctors upon Book II of the Sentences, distinctions 10 and 11.