"The conscience of fallen human beings is often mistaken (it needs to be educated by the Word of God) and often sleepy (it needs to be awakened by the Spirit of God).  True also, some people deny that they have any sense of sin, insisting at the same time that everything is relative now, for there are no moral absolutes anymore.  Do not believe them.  For by creation God still endows all human beings with a moral sense, which our inherited fallenness has distorted but not destroyed.  Unless and until people so violate and smother their conscience as to 'cauterize' it (a word Paul uses in 1 Tim. 4:2) or render it insensitive, it continues to trouble them.  They know they are sinful and guilty, however much they may protest to the contrary."

– John R.W. Stott