Since particular faculties are governed by universal ones, angels have charge over material things. For it is evident that the power of a body is more limited than that of a spiritual substance; because corporeal forms are individuated, and exactly determined by matter, while spiritual forms are absolute and intelligible; hence, as the inferior angels, whose forms are less universal, are governed by the superior ones, so all material forms are governed by angels.
We must not conclude on this account, that one angel is fitted by nature to have charge of animals rather than of plants, for the lowest angel possesses higher and more universal faculties than any species of corporeal things; but the order established by Divine Wisdom assigns the administration of various things to various powers.
Neither does it follow that the angelic Orders are more in number than nine, for they are distinguished by their general offices only.
Nor are we to conclude that corporeal nature is subject to the angels directly, as regards transmutation of form; for whatever is composed of matter and form is developed, and, as such, produced from that which is like itself. Hence formal transmutation is only effected by composite things, or by Him Who contains composition - that is to say, matter of form - in a more eminent manner, i.e. by God, Who alone creates, and to Whose command only matter is directly subject.
Nevertheless, matter is directly subject to spiritual substances as regards local motion; for an inferior nature attains its highest level by means of a superior one. Thus corporeal nature attains to local motion, which is motion of the most perfect kind, through this spiritual nature: accordingly we see that the soul moves the body first, and chiefly by way of local motion.
Neither can angels work miracles; for a miracle is something done contrary to the whole course of Nature. Therefore it does not suffice for the conception of a miracle that the thing done be contrary to a particular law of Nature, or else to throw a stone upwards would be a miracle. Thus, properly speaking, God alone works miracles, beyond the entire order of Nature; and whatever an angel or any other creature does by its own power is according to the order of Nature; and if angels or saints are said to work miracles, it is either because they exercise some ministry in regard of them, or because God works the miracle at their desire.
- text taken from Compendium of the Summa Theologica of Saint Thomas Aquinas, by Bishop Berardus Bongiovanni