Whether sin is fittingly defined as a word, deed, or desire contrary to the eternal law?

❌ Objection 1 : It would seem that sin is unfittingly defined by saying: "Sin is a word, deed, or desire, contrary to the eternal law." Because "Word," "deed," and "desire" imply an act; whereas not every sin implies an act, as stated above (Article [5]). Therefore this definition does not include every sin.

❌ Objection 2 : Further, Augustine says (De Duab. Anim. xii): "Sin is the will to retain or obtain what justice forbids." Now will is comprised under desire, in so far as desire denotes any act of the appetite. Therefore it was enough to say: "Sin is a desire contrary to the eternal law," nor was there need to add "word" or "deed."

❌ Objection 3 : Further, sin apparently consists properly in aversion from the end: because good and evil are measured chiefly with regard to the end as explained above (Question [1], Article [3]; Question [18], Articles [4],6; Question [20], Articles [2],3): wherefore Augustine (De Lib. Arb. i) defines sin in reference to the end, by saying that "sin is nothing else than to neglect eternal things, and seek after temporal things": and again he says (Qq. lxxxii, qu. 30) that "all human wickedness consists in using what we should enjoy, and in enjoying what we should use." Now the definition is question contains no mention of aversion from our due end: therefore it is an insufficient definition of sin.

❌ Objection 4 : Further, a thing is said to be forbidden, because it is contrary to the law. Now not all sins are evil through being forbidden, but some are forbidden because they are evil. Therefore sin in general should not be defined as being against the law of God.

❌ Objection 5 : Further, a sin denotes a bad human act, as was explained above (Article [1]). Now man's evil is to be against reason, as Dionysius states (Div. Nom. iv). Therefore it would have been better to say that sin is against reason than to say that it is contrary to the eternal law.