One of the more interesting developments of Christian theology in the west was the development of the 'conscience.' Two years ago, I summarized Oliver O'Donovan on this theme:
Clearly, we do sin sometimes. In those moments, we develop a self-awareness of the dividedness between our reason and our will, a “guilty self-awareness” that is often called the ‘conscience.’ O’Donovan argues that while this meaning of conscience is present in the letters of Paul, the medieval and moderns understand conscience as “the whole faculty of moral understanding and self-direction.” In doing so, they make the separation of reason and will normative, not an effect of sin, which “generates a conception of freedom as autonomy, the agent’s independence of reality.” That is, while Paul understood “conscience” to be part of the human response to sin, subsequent Christian thinkers made it an intrinsic part of human nature.
It is fascinating to read John Calvin's definition of conscience in light of O'donovan's analysis. Writes Calvin (III.19.15):
For just as when throught he mind and understanding men grasp a knowledge of things, and from this are said "to know," this is the source of the word "knowledge," so also when they have a sense of divine judgment, as a witness joined to them, which does not allow them to hide their sins from being accused before the Judge's tribunal, this sense is called "conscience." For it is a certain mean between God and man, because it does not allow man to suppress within himself what he knows, but pursues him to the point of convicting him...Therefore this awareness which hales man before God's judgment is a sort of guardian appointed for man to note and spy out all his secrets that nothing may be buried in darkness."
Calvin is clearly comfortable describing 'conscience' both as a faculty and as a particular sort of awareness of God's judgment.
But he also argues that even as a faculty of the soul, it has specific reference to God, not man. Calvin writes, "As works have regard to men, so conscience refers to God." While Luke records Paul declaring that he took pains to walk "with a clear conscience toward God and men," Calvin contends that "this was said because the fruit of a good conscience flows forth and comes even to men. But properly speaking, as I have already said, it has respect to God alone."
This is all the more interesting in light of our current usage of "conscience." While we clearly treat it as a "faculty" of the soul (like the mind), we have neutered it in two important ways:
First, we divorce our consciences from any normative, external ethical system (like natural law), subjectivizing them in such a way that ethical direction depends upon its "proper functioning." If you have a "seared conscience" and want to know what's right or wrong in any given situation, alas, you're out of luck.
Second, "conscience' lacks the specifically "God-oriented" aspect of judgment that it clearly has for Calvin. There is no transcendent aspect, no awareness not just that I am wrong, but that I am wrong before the Maker and Ruler of the universe. For Calvin, the conscience is a middle ground precisely because as a faculty of the soul, it reaches beyond itself and makes us aware of our standing before God.
Our contemporary understanding of 'conscience' has none of that. So what are they left with? Only themselves, and their history. They are by themselves and for themselves, and so can be nothing other than curved in on themselves.