On the contrary, The perfection of an angel is greater than that of man in the primitive state.  But man could not sin venially in the primitive state, and much less, therefore, can an angel.

I answer that, An angel’s intellect, as stated above in the First Part (Q. 58, A. 3; Q. 79, A. 8), is not discursive, i.e. it does not proceed from principles to conclusions, so as to understand both separately, as we do.  Consequently, whenever the angelic intellect considers a conclusion, it must, of necessity, consider it in its principles.  Now in matters of appetite, as we have often stated (Q. 8, A. 2; Q. 10, A. 1; Q. 72, A. 5), ends are like principles, while the means are like conclusions.  Wherefore, an angel’s mind is not directed to the means, except as they stand under the order to the end.  Consequently, from their very nature, they can have no inordinateness in respect of the means, unless at the same time they have an inordinateness in respect of the end, and this is a mortal sin.  Now good angels are not moved to the means, except in subordination to the due end which is God:  wherefore all their acts are acts of charity, so that no venial sin can be in them.  On the other hand, wicked angels are moved to nothing except in subordination to the end which is their sin of pride.  Therefore they sin mortally in everything that they do of their own will.  This does not apply to the appetite for the natural good, which appetite we have stated to be in them (I, Q. 63, A. 4; Q. 64, A. 2, ad 5).

Reply Obj. 1:  Man does indeed agree with the angels in the mind or intellect, but he differs in his mode of understanding, as stated above.

Reply Obj. 2:  An angel could not love a creature less than God, without, at the same time, either referring it to God, as the last end, or to some inordinate end, for the reason given above.

Reply Obj. 3:  The demons incite man to all such things which seem venial, that he may become used to them, so as to lead him on to mortal sin.  Consequently in all such things they sin mortally, on account of the end they have in view. ________________________

FIFTH ARTICLE [I-II, Q. 89, Art. 5]

Whether the First Movements of the Sensuality in Unbelievers Are
Mortal Sin?

Objection 1:  It would seem that the first movements of the sensuality in unbelievers are mortal sins.  For the Apostle says (Rom. 8:1) that “there is . . . no condemnation to them that are in Christ Jesus, who walk not according to the flesh”:  and he is speaking there of the concupiscence of the sensuality, as appears from the context (Rom. 7).  Therefore the reason why concupiscence is not a matter of condemnation to those who walk not according to the flesh, i.e. by consenting to concupiscence, is because they are in Christ Jesus.  But unbelievers are not in Christ Jesus.  Therefore in unbelievers this is a matter of condemnation.  Therefore the first movements of unbelievers are mortal sins.