All things incline towards good in their own way. Some are so by nature only, without understanding; as plants and inanimate things, in which there is a natural bias; some with a certain amount of cognizance, where they know a particular good; as the senses know sweetness, colour, and so on; the inclination which follows such recognition being called sensitive appetite. Others incline to good with a cognizance by which they know this same conception of goodness; this is proper to the intellect, and is called Will; and will is attributed to the angels because their intellect is cognizant of the universal conception of goodness.
This will is not the same as their essence, because it does not belong to the essence of anything to extend to that which is outside itself, whereas the will of the angels extends to willing an infinite good. In God only, as already explained, Essence and Will are the same; for in Him all good is contained, nor does He Will anything outside Himself except by reason of His Goodness; which is impossible with creatures. Moreover, it is only by the power of another that the intellect can possess that which is external to itself and be perfected by it. The will tends, indeed, thereto; but to possess, and to tend towards something else belong to different faculties; hence in creatures essence and will are diverse.
Since there are three different kinds of agents, namely, natural things without choice, sensible things with choice but without liberty, and intellectual beings with choice and liberty, the angels, who possess a higher intelligence than men, possess free will in regard of that which they apprehend under the general conception of good, and free will also in judging.
Angels, having intellectual appetite only, have nothing of the concupiscible or the irascible passions. For faculties are distinguished by the formal nature of their object, and the object of the will is good, according to the general conception of goodness. Hence the intellectual appetite is not differentiated according to particular kinds of good, like the sensitive appetite, which does not exist in the angels; and acts which are dependent upon such faculties are attributed to the angels only metaphorically. Thus love and joy belong to them, not as passions but as simple affections of the will; and so of others.
- text taken from Compendium of the Summa Theologica of Saint Thomas Aquinas, by Bishop Berardus Bongiovanni