Question Four of Chapter Three of the Second Decade
That, notwithstanding divine governance, the guardianship of angels also ought to be given
It is doubted why human beings need the guardianship of the weaker angels when the guardianship of the stronger God is always present to them.
To this it is answered as follows: according to the nature of divine providence, this is found in all things—that movable and variable things are always moved through immovable things—because, as the Philosopher teaches, every motion proceeds naturally from something immovable.
Whence we see that the lower bodies are ruled by the higher bodies, in which there is less change and motion; and thus corporeal things are moved and ruled by incorporeal things, namely by spiritual substances.
Whence also the terms and probable propositions of a certain question are strengthened by immovable and invariable things, namely principles known through themselves, and are reduced to them.
But it is manifest that in things to be done human beings can fail in many ways both from the due end and from the manner of acting. And therefore, in order that a human being might more fittingly arrive at his end, it was necessary that through some angel, as one more perfect than himself, he should be withdrawn from evil and advanced in good; and this we call the guardianship of angels.
But as regards the motivating objection, when it is said that there is no need for the guardianship of a weaker angel when the most mighty God is present, “who shall neither slumber nor sleep, guarding Israel,” it must be said that two things are required for acting well.
First, that the will be inclined toward good. Second, that suitable means be possessed for accomplishing the good.
As regards the first, God guards a human being immediately by infusing grace into him together with the virtues.
But as regards the second, God guards a human being by instructing him through angels as intermediaries.
For example: just as among craftsmen one cause disposes something for a form, and another cause introduces the form—as fire disposes something for the form of a knife by softening the iron, the hammer by spreading out the iron, and the craftsman, as principal agent, introduces the form of the knife—so it is the office of angels to prepare human beings for grace and glory through illuminations and things of this sort which operate instrumentally concerning us.
But it belongs to God, as principal agent and guardian, to give the final perfection: namely, grace joining us to consummated grace and to the final end, namely glory.
These things are from Thomas, Book II of the Sentences, distinction 11, question 1, article 1, in the two arguments to the contrary, in the body of the question, and in the solutions of the first and second arguments; and Alexander, Second Part of the Summa, question 40, article 1.