What are some of the things angels can and can’t do in the created order? One thing Thomas is quite clear on in regards to angelic power is that they cannot create. Nor, for that matter, does Thomas believe that angels can even communicate substantial form to already created matter (i.e., they can no more sub-create new things than they can create them). The primary reason Thomas gives for this in the Summa is that, because “like is produced from like,” we are not to “look for the cause of corporeal forms in any immaterial form” (ST 1.65.4). As immaterial and incorporeal entities, in other words, angels are not a “proportionate” and therefore fitting and capable cause of the forms of material and corporeal substances. At the same time, Thomas is adamant that angelic intelligences, as the highest of created beings, are more not less powerful than lower beings, including even the human soul, which can directly move only the body it is united to and other bodies only through it; whereas angels, by contrast, can move bodies they are not naturally united to (ST 1.110.3 ad 3). One way of viewing Thomas’s concern, accordingly, is to see him as at once claiming on the angels’ behalf the most far-reaching power and influence among created beings, without at the same time compromising the integrity and natural operation of the sub-angelic, corporeal order.
Thus, whereas angels exert a greater and more universal power and influence over bodies than even bodies and human souls are able to do, this angelic power and influence is accomplished not by effecting substantial change in things, but rather through what Thomas (following Aristotle) regards as the most perfect form of motion or change, namely local motion. The local motion of bodies induced by angels, furthermore, is accomplished principally through their moving the celestial spheres, the regular alteration of which causes the cycles of generation and corruption in the sub-lunar sphere of Earth. In this way the local motion of the heavenly bodies serves as a sort of cosmic, diffusing lens through which the otherwise expansive power of the angels is mediated, accommodated, and focused or concentrated to the kind of limited, passive potentialities proper to corporeal existence.
 “[C]um simile fiat a suo simili, non est quaerenda causa formarum corporalium aliqua forma immaterialis; sed aliquod compositum…”
 Collins, in a chapter devoted exclusively to the subject of angelic power, elaborates on this particular Thomistic limit: “While that which is potential in matter is present in a more noble way in separated substances [i.e., angels], yet corporeal matter is not a proportionate potentiality with respect to the act whereby spiritual substances are in act. This follows from the fact that it is the composite itself rather than its components that is properly and essentially generated. Because of this necessary disproportion, no created spiritual substance has the power to effect an immediate substantial change in matter. The intermediate agency of some natural cause is required for such a formal transmutation… As higher forms, separated substances possess supremely universal active powers to which the passive powers of lower substances are not sufficiently adapted to receive an actualization except through the mediation of natural agents.” Collins, The Thomistic Philosophy of the Angels, 313-14.
 Thomas following Augustine leaves undecided the historic debate as to whether the angels are joined to the heavenly bodies as their animating forms, i.e., the thesis that the heavenly bodies are “ensouled” by angels—the position of Plato, Aristotle, Origen, and Jerome—or whether the angels are united to them merely as external movers—the view of Anaxagoras, Basil, and John Damascene. Thomas’s inclination, however, is towards the latter of the two positions. Collins, The Thomistic Philosophy of the Angels, 306-10.