Conscience is not so much the voice of God in us, as the voice of our social environment. It judges us according to its own laws. Conscience attributes to me alone the guilt of an action which was the end result of the influence of thousands of other people; ancestors through heredity; teachers and parents who gave me an education; authors, actors, friends and enemies who moulded my soul; the pressure of my social environment; etc.
Conscience is biased. It will remind you only of the bad things, the good it forgets. To appear before God absolutely free from guilt is completely unacceptable to conscience. It is totally unable to grasp the that not only the sinner, but also the sin, can become white as snow.
I am greater than my sins.
Conscience would try to identify me with them. The only criterion of a deed is; does it prepare the way for the final triumph of love? Or not?
We have to choose between good as the means, and good as the end.
If I am always good towards all men, even those who by deceit and terror hinder the victory of love, good will never triumph. The wicked profit by my meekness, and consolidate the position of evil. If I choose good as my goal, I have to commit actions which are condemned as evil in the moral catalogue of the world.
How can it be possible then, that conscience comes from God?