There are interior and exterior sources of Sin.
2. We will take, first, the interior sources of Sin. These are three—(a) Culpable ignorance; (b) Human fragility; (c) Malice.
3. Culpable ignorance. A man is guilty when he commits an act which is sinful, or omits to fulfil a duty, not knowing that the act is sinful, or that the duty is obligatory, through ignorance, but through ignorance which is voluntary, because he has neglected to learn what is his duty and what are the commandments of God, or else, because having learnt, he has allowed his knowledge to lapse, and he no longer keeps in mind what he once learnt; or else, because by trifling with his conscience he has so confused it that it no longer speaks distinctly and emphatically, telling him what to do and what to avoid. Consequently, we are bound to use our best endeavours to learn exactly what is the Will of God, and having learnt to keep in mind what has been acquired, and so promptly, and without prevarication, to obey our consciences that they may not become to us uncertain in their utterances.
We may be, and we shall be, excused if we have sinned through involuntary ignorance, but not if we have neglected the opportunities placed in our way of learning our duty.
4. Human frailty. The weakness of our mortal nature is prone to let us be drawn away into evil, either through—
(a) The violence of temptation; or
(b) The weakness of our resolution; or
(c) The force of bad habit; or
(d) The warmth and concupiscence of imagination.
5. Temptation is strong. Temptations are from without and from within. It is necessary to recognize the fact that we are being tempted in order that we may be prepared to resist. Half the sins fallen into are committed before we have realized that we are in temptation. Therefore we pray that we may not be led into temptation.