Answer
Natural law is essentially the moral content of general revelation. Natural law THEORY consists of various views of how to extract and use that moral content.
Natural law theorists differ somewhat among themselves. Since I wrote that paper, I've read books by Jay Budziszewski, which I've found very impressive. He uses natural law mainly as a moral argument for God's existence and then as an indication that we need much more than NL, which we find in Scripture. I disagree with Jay on a few things, but generally he and I are in synch.
Roman Catholic versions of NL theory tend to be unpersuasive to me. The idea that birth control is wrong because it breaks a "natural" connection between sex and procreation seems to me to be an example of the naturalistic fallacy. Further, I disagree with the "two kingdom" folks who think that we should try to enforce politically only the contents of natural law and not the contents of Scripture. Rather, I believe that Christ is Lord of all, even politics, and that our goal should be nothing less than a Christian society.
Indeed, I believe that you can't adequately understand NL without the spectacles of Scripture.
The primary purpose of NL-General Revelation is of course to glorify God (Psm. 19:1). That's true of everything. The more specific purpose of General Rev. is to leave the unbeliever with no excuse for his sin (Rom. 1). But GR also, of course, serves to help the believer apply Scripture to his daily decisions. It furnishes minor premises for moral syllogisms.
Answer by Dr. John M. Frame
Dr. John M. Frame is Professor of Systematic Theology and Philosophy at Reformed Theological Seminary in Orlando, FL.