1 Objection 1: It would seem that the angels do not differ in species. For since the difference is nobler than the genus, all things which agree in what is noblest in them, agree likewise in their ultimate constitutive difference; and so they are the same according to species. But all angels agree in what is noblest in them, that is to say, in intellectuality. Therefore all the angels are of one species.
1 Ad quartum sic proceditur. Videtur quod Angeli non differant specie. Cum enim differentia sit nobilior genere, quaecumque conveniunt secundum id quod est nobilissimum in eis, conveniunt in ultima differentia constitutiva; et ita sunt eadem secundum speciem. Sed omnes Angeli conveniunt in eo quod est nobilissimum in eis, scilicet in intellectualitate. Ergo omnes Angeli sunt unius speciei.
2 Objection 2: Further, more and less do not change a species. But the angels seem to differ only from one another according to more and less, namely, as one is simpler than another, and of keener intellect. Therefore the angels do not differ specifically.
2 Praeterea, magis et minus non diversificant speciem. Sed Angeli non videntur differre ad invicem nisi secundum magis et minus; prout scilicet unus alio est simplicior, et perspicacioris intellectus. Ergo Angeli non differunt specie.
3 Objection 3: Further, soul and angel are contra-distinguished mutually from each other. But all souls are of the one species. So therefore are the angels.
3 Praeterea, anima et Angelus ex opposito dividuntur. Sed omnes animae sunt unius speciei. Ergo et Angeli.
4 Objection 4: Further, the more perfect a thing is in nature, the more ought it to be multiplied. But this would not be so if there were but one individual under one species. Therefore there are many angels of one species.
4 Praeterea, quanto aliquid est perfectius in natura, tanto magis debet multiplicari. Hoc autem non esset, si in una specie esset unum tantum individuum. Ergo multi Angeli sunt unius speciei.
5 On the contrary, In things of one species there is no such thing as first and second prius et posterius), as the Philosopher says Metaph. iii, text 2). But in the angels even of the one order there are first, middle, and last, as Dionysius says Hier. Ang. x). Therefore the angels are not of the same species.
5 Sed contra est quod in his quae sunt unius speciei, non est invenire prius et posterius, ut dicitur in III Metaphys. Sed in Angelis, etiam unius ordinis, sunt primi et medii et ultimi, ut dicit Dionysius, X cap. Ang. Hier. Ergo Angeli non sunt eiusdem speciei.
6 I answer that, 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 Article 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.
6 Respondeo dicendum quod quidam dixerunt omnes substantias spirituales esse unius speciei, etiam animas. Alii vero quod omnes Angeli sunt unius speciei, sed non animae. Quidam vero quod omnes Angeli unius hierarchiae, aut etiam unius ordinis. Sed hoc est impossibile. Ea enim quae conveniunt specie et differunt numero, conveniunt in forma, et distinguuntur materialiter. Si ergo Angeli non sunt compositi ex materia et forma, ut dictum est supra, sequitur quod impossibile sit esse duos Angelos unius speciei. Sicut etiam impossibile esset dicere quod essent plures albedines separatae, aut plures humanitates; cum albedines non sint plures nisi secundum quod sunt in pluribus substantiis. Si tamen Angeli haberent materiam, nec sic possent esse plures Angeli unius speciei. Sic enim oporteret quod principium distinctionis unius ab alio esset materia, non quidem secundum divisionem quantitatis, cum sint incorporei, sed secundum diversitatem potentiarum. Quae quidem diversitas materiae causat diversitatem non solum speciei, sed generis.
7 Reply to Objection 1: Difference is nobler than genus, as the determined is more noble than the undetermined, and the proper than the common, but not as one nature is nobler than another; otherwise it would be necessary that all irrational animals be of the same species; or that there should be in them some form which is higher than the sensible soul. Therefore irrational animals differ in species according to the various determined degrees of sensitive nature; and in like manner all the angels differ in species according to the diverse degrees of intellectual nature.
7 Ad primum ergo dicendum quod differentia est nobilior genere, sicut determinatum indeterminato et proprium communi; non autem sicut alia et alia natura. Alioquin oporteret quod omnia animalia irrationalia essent unius speciei; vel quod esset in eis aliqua alia perfectior forma quam anima sensibilis. Differunt ergo specie animalia irrationalia secundum diversos gradus determinatos naturae sensitivae. Et similiter omnes Angeli differunt specie secundum diversos gradus naturae intellectivae.
8 Reply to Objection 2: More and less change the species, not according as they are caused by the intensity or remissness of one form, but according as they are caused by forms of diverse degrees; for instance, if we say that fire is more perfect than air: and in this way the angels are diversified according to more or less.
8 Ad secundum dicendum quod magis et minus, secundum quod causantur ex intensione et remissione unius formae, non diversificant speciem. Sed secundum quod causantur ex formis diversorum graduum, sic diversificant speciem, sicut si dicamus quod ignis est perfectior aere. Et hoc modo Angeli diversificantur secundum magis et minus.
9 Reply to Objection 3: The good of the species preponderates over the good of the individual. Hence it is much better for the species to be multiplied in the angels than for individuals to be multiplied in the one species.
9 Ad tertium dicendum quod bonum speciei praeponderat bono individui. Unde multo melius est quod multiplicentur species in Angelis, quam quod multiplicentur individua in una specie.
10 Reply to Objection 4: Numerical multiplication, since it can be drawn out infinitely, is not intended by the agent, but only specific multiplication, as was said above Question 47, Article 3). Hence the perfection of the angelic nature calls for the multiplying of species, but not for the multiplying of individuals in one species.
10 Ad quartum dicendum quod multiplicatio secundum numerum, cum in infinitum protendi possit, non intenditur ab agente, sed sola multiplicatio secundum speciem, ut supra dictum est. Unde perfectio naturae angelicae requirit multiplicationem specierum, non autem multiplicationem individuorum in una specie.