A formal sin is committed knowingly and wilfully; a material sin is committed without knowledge or free consent.
Sin is said to be against God, our neighbour, or ourself, as it is against some virtue which immediately regards God, or our neighbour, or ourself. All sin is ultimately against God.
Sins of ignorance are committed through culpable ignorance; sins of infirmity through passion or bad habit; sins of malice with cool deliberation and forethought. The last, as is obvious, are the least excusable.
A sin of commission is an act against a negative precept; a sin of omission is the wilful neglect of a positive precept.
The meaning of the terms sins of thought, word, and deed, is obvious.
3. To commit sin there must be actual advertence to the malice of the action done, either when the action is performed, or when the cause is put. This follows from what was said above about human acts, which must be voluntary either in themselves or at any rate in their cause. But no act is voluntary without previous knowledge and advertence. It is not sufficient, then, for sin that a man could physically advert to the wrongfulness of his action, and should have done so; if there was no advertence, either at the time of the action or when its cause was put, there is no sin. However, advertence to what is likely to follow when the cause is put is sufficient to contract the malice of sin; and so wrong done through wilful negligence, or passion, or habit, or carelessness, is imputable to the agent.
Advertence to an evil thought or motion does not constitute sin without free consent of the will. The will consents when it voluntarily accepts an evil suggestion presented by the mind, and it is immaterial whether the evil originates in the will, or whether the will accedes to evil when suggested to it from without. For sin, then, there must be both advertence to the evil and free consent to it; a man who takes another's money, thinking it to be his own, does not commit theft, nor does the kleptomaniac who is powerless to refrain.
