Objection 1. It would seem that there is no will in the angels. For as the Philosopher says (De Anima iii, text. 42), "The will is in the reason." But there is no reason in the angels, but something higher than reason. Therefore there is no will in the angels, but something higher than the will.
Objection 2. Further, the will is comprised under the appetite, as is evident from the Philosopher (De Anima iii, text. 42). But the appetite argues something imperfect; because it is a desire of something not as yet possessed. Therefore, since there is no imperfection in the angels, especially in the blessed ones, it seems that there is no will in them.
Objection 3. Further, the Philosopher says (De Anima ii, text. 54) that the will is a mover which is moved; for it is moved by the appetible object understood. Now the angels are immovable, since they are incorporeal. Therefore there is no will in the angels.
On the contrary, Augustine says (De Trin. x, 11,12) that the image of the Trinity is found in the soul according to memory, understanding, and will. But God's image is found not only in the soul of man, but also in the angelic mind, since it also is capable of knowing God. Therefore there is will in the angels.
I answer that, We must necessarily place a will in the angels. In evidence thereof, it must be borne in mind that, since all things flow from the Divine will, all things in their own way are inclined by appetite towards good, but in different ways. Some are inclined to good by their natural inclination, without knowledge, as plants and inanimate bodies. Such inclination towards good is called "a natural appetite." Others, again, are inclined towards good, but with some knowledge; not that they know the aspect of goodness, but that they apprehend some particular good; as in the sense, which knows the sweet, the white, and so on. The inclination which follows this apprehension is called "a sensitive appetite." Other things, again, have an inclination towards good, but with a knowledge whereby they perceive the aspect of goodness; this belongs to the intellect. This is most perfectly inclined towards what is good; not, indeed, as if it were merely guided by another towards some particular good only, like things devoid of knowledge, nor towards some particular good only, as things which have only sensitive knowledge, but as inclined towards good in general. Such inclination is termed "will." Accordingly, since the angels by their intellect know the universal aspect of goodness, it is manifest that there is a will in them.
Reply to Objection 1. Reason surpasses sense in a different way from that in which intellect surpasses reason. Reason surpasses sense according to the diversity of the objects known; for sense judges of particular objects, while reason judges of universals. Therefore there must be one appetite tending towards good in the abstract, which appetite belongs to reason; and another with a tendency towards particular good, which appetite belongs to sense. But intellect and reason differ as to their manner of knowing; because the intellect knows by simple intuition, while reason knows by a process of discursion from one thing to another. Nevertheless by such discursion reason comes to know what intellect learns without it, namely, the universal. Consequently the object presented to the appetitive faculty on the part of reason and on the part of intellect is the same. Therefore in the angels, who are purely intellectual, there is no appetite higher than the will.
Reply to Objection 2. Although the name of the appetitive part is derived from seeking things not yet possessed, yet the appetitive part reaches out not to these things only, but also to many other things; thus the name of a stone [lapis] is derived from injuring the foot [laesione pedis], though not this alone belongs to a stone. In the same way the irascible faculty is so denominated from anger [ira]; though at the same time there are several other passions in it, as hope, daring, and the rest.
Reply to Objection 3. The will is called a mover which is moved, according as to will and to understand are termed movements of a kind; and there is nothing to prevent movement of this kind from existing in the angels, since such movement is the act of a perfect agent, as stated in De Anima iii, text. 28.
Source: Summa Theologica (New Advent)