(ibid) Some have said that all spiritual substances, even souls, are of the one species. Others, again, that all the angels are of the one species, but not souls; while others allege that all the angels of one hierarchy, or even of one order, are of the one species.
But this is impossible. For such things as agree in species but differ in number, agree in form, but are distinguished materially. If, therefore, the angels be not composed of matter and form, as was said above (2), it follows that it is impossible for two angels to be of one species; just as it would be impossible for there to be several whitenesses apart, or several humanities, since whitenesses are not several, except in so far as they are in several substances. And if the angels had matter, not even then could there be several angels of one species. For it would be necessary for matter to be the principle of distinction of one from the other, not, indeed, according to the division of quantity, since they are incorporeal, but according to the diversity of their powers; and such diversity of matter causes diversity not merely of species, but of genus. |
