A. Sin is Formally the Privation of Good

33. Although these questions, according to the Master, belong to different distinctions, yet their solutions are connected, and because of this connection in this way they can be asked together; and among these questions the first to be solved is the second [n.10], because its solution occupies a place in the others.

And although one could preface here without proof what the word ‘sin’ means (for before any questioning about anything there is need first to have knowledge of what the word means), nevertheless that sin is formally the privation of good is shown by the authorities adduced for the opposite [n.14], and by the following sort of reason, that an inferior agent is bound in its acting to conform itself to the superior agent, because if it is in its power to conform or not conform then not to conform is a sin. For that is why it is called ‘sin’ (speaking of sin whether against divine law or against human law), because the one sinning could have conformed to the law of the superior agent and did not. Therefore the act which is in the power of the non-conformer, and which is thereby voluntary, is not formally sin, because it would not be a sin if it did conform to the superior rule; so the idea of sin in that act is precisely the privation of the conformity.