CCC #1778 Conscience is a judgement of reason. CCC #1790 A human being must always obey the certain judgement of his conscience... Yet it can happen that moral conscience... makes erroneous judgements... CCC #1791 This is the case when a man "takes little trouble to find out what is true and good, or when conscience is by degrees almost blinded through the habit of committing sin." In such cases, the person is culpable for the evil he commits.