The natural conscience is no distinct faculty, but the one intellect of a man inasmuch as it considers right and wrong in conduct, aided meanwhile by a good will, by the use of the emotions, by the practical experience of living, and by all external helps that are to the purpose.
The natural conscience of the Christian is known by him to act not alone, but under the enlightenment and the impulse derived from revelation and grace in a strictly supernatural order.
As to the order of nature, which does not exist but which might have existed, St. Thomas (I-II:109:3) teaches that both for the knowledge of God and for the knowledge of moral duty, men such as we are would require some assistance from God to make their knowledge sufficiently extensive, clear, constant, effective, and relatively adequate; and especially to put it within reach of those who are much engrossed with the cares of material life. It would be absurd to suppose that in the order of nature God could be debarred from any revelation of Himself, and would leave Himself to be searched for quite irresponsively.
Being a practical thing, conscience depends in large measure for its correctness upon the good use of it and on proper care taken to heed its deliverances, cultivate its powers, and frustrate its enemies.
Even where due diligence is employed conscience will err sometimes, but its inculpable mistakes will be admitted by God to be not blameworthy. These are so many principles needed to steady us as we tread some of the ways of ethical history, where pitfalls are many.
