John Frame has, I think, done the Church a great service in writing The Doctrine of the Christian Life. It is the material from his course on Christian Ethics. The 3rd section of the book is Christian Ethical Methodology. As expected, he breaks this into 3 parts: normative, situational and existential.
“In general, a Christian ethical decision is the application of God’s revelation (normative) to a problem (situational) by a person (existential).”
The normative aspect of Christian Ethics is revelation. God exercises His lordship by communicating His character and will to us. Unlike non-Christian views of deontological ethics, we have a recognizable standard. Frame affirms both general and special revelation as part of that standard. Both can be misinterpreted by sinners such as us.
We don’t just have a Law given to us. God expects us to imitate Him. He is the ultimate norm for us. There is an aspect of “What Would Jesus Do” that is accurate.
But the overall focus is the authority of Scripture. He spends time on inspiration and the attributes of Scripture. He has an important chapter on the sufficiency of Scripture. This is often misunderstood. The Westminster Confession formulates the sufficiency of Scripture “concerning all things necessary for his own glory, man’s salvation, faith and life.” It does not limit this to explicit statements (a problem I often run into in theological discussion), but also includes “any good and necessary consequence.” In other words, doing theology is not merely quoting Scripture but THINKING through the consequences of what Scripture says. As a result, the divine words we have are sufficient for our needs.
“The sufficiency of Scripture does not rule out the use of natural revelation (“the light of nature”) and human reasoning (“Christian prudence”) in our decisions, even when those decisions concern the worship and government of the church.”