Conscience is, as it were, the most intimate and secret core of man. There he takes refuge with his spiritual faculties in absolute solitude. There he is alone with himself or, better, alone with himself and God, whose voice conscience echoes. There man decides to do good or to do evil; there he chooses the road to victory or the road to defeat. Though sometimes he may want to, man can never divest himself of his conscience. Approving or disapproving of what he does, his conscience will accompany him all the days of his life; and it will also be with him, as a true and incorruptible witness, when he appears before God's judgment seat.

(Pope Pius XII)