Sin

7:7. What shall we say, then? Is the law sin? God forbid! But I do not know sin, but by the law. For I had not known concupiscence, if the law did not say: Thou shalt not covet.

7:8. But sin, taking occasion by the commandment, wrought in me all manner of concupiscence. For without the law sin was dead.

7:9. And I lived some time without the law. But when the commandment came, sin revived,

7:10. And I died. And the commandment that was ordained to life, the same was found to be unto death to me.

7:11. For sin, taking occasion by the commandment, seduced me: and by it killed me.

7:12. Wherefore the law indeed is holy: and the commandment holy and just and good.

7:13. Was that then which is good made death unto me? God forbid! But sin, that it may appear sin, by that which is good, wrought death in me: that sin, by the commandment, might become sinful above measure.

3:4. Whosoever committeth sin committeth also iniquity. And sin is iniquity.

3:5. And you know that he appeared to take away our sins: and in him there is no sin.

3:6. Whosoever abideth in him sinneth not: and whosoever sinneth hath not seen him nor known him.

3:7. Little children, let no man deceive you. He that doth justice is just, even as he is just.

3:8. He that committeth sin is of the devil: for the devil sinneth from the beginning. For this purpose the Son of God appeared, that he might destroy the works of the devil.

As was shown above, sin is nothing else than a bad human act. Now that an act is a human act is due to its being voluntary, as stated above, whether it be voluntary, as being elicited by the will, e.g. to will or to choose, or as being commanded by the will, e.g. the exterior actions of speech or operation. Again, a human act is evil through lacking conformity with its due measure: and conformity of measure in a thing depends on a rule, from which if that thing depart, it is incommensurate. Now there are two rules of the human will: one is proximate and homogeneous, viz. the human reason; the other is the first rule, viz. the eternal law, which is God's reason, so to speak. Accordingly Augustine (Contra Faust. xxii, 27) includes two things in the definition of sin; one, pertaining to the substance of a human act, and which is the matter, so to speak, of sin, when he says "word," "deed," or "desire"; the other, pertaining to the nature of evil, and which is the form, as it were, of sin, when he says, "contrary to the eternal law."