Protestants have differed on whether natural law with its excessive use of reason and its antecedents in Aristotle is compatible at all with biblical Christianity. Francis Schaeffer, for instance, didn't think so. Tom Van Dyke, in this comment, nicely sums up why Christianity and natural law are compatible:
Paul in the Epistles sez that the natural law is written on man's heart. That's how Aquinas could give the pagan pre-Christian-era Aristotle his props.
It's not "reason" exactly. It's our human nature, our humanity itself, just as God created us. Some soft spot that lets us love art and not be robots. Aristotle found his way not only with an open mind but with an open heart. Aristotle was a mensch. If you know your Yiddish, a mensch has a brain and a heart. Otherwise, he's not a man.
Compare Aristotle with [the modernist] Thomas Hobbes, who made a damn good argument that we're just sophisticated and calculating social animals, and you see the difference.
America's Protestant natural lawyers rarely cited Aquinas but they did cite Locke, who in turn cited Hooker who in turn was the Anglican heir to Aquinas. AND the Founders loved Aristotle as well.
But one thing to understand about the natural law -- and this is something that Christian America apologists often don't get -- is that it defines as what man discovers from reason. And, though, ultimately "Christian" natural law believes in the synthesis and perfect agreement of reason and revelation, it eschews simply looking up verses and chapters of the Bible as proof texts and quoting them as trumping authority. So if one is a Protestant like Francis Schaeffer who likes to do that because man's unregenerate reason is the "devil's whore" as it were, the natural law of the American Founding (i.e., "the laws of nature and nature's God") is not likely to resonate with you.
And so it is that I am going to post a long excerpt from James Wilson's Works. Wilson was one of the most important Founding Fathers, one of six (I believe) who signed the Declaration and the US Constitution. And he played a key role at the Constitutional Convention. And, as a common lawyer and expositor of how Americans viewed "the laws of nature and nature's God," he is a much better authority than Blackstone who was an English Tory who believed in the very Parliamentary supremacy against which America revolted.
Wilson's theories, as we will see shortly, are certainly reminiscent of Aquinas'. After quoting this long excerpt, my next post will feature some reasons why evangelicals/fundamentalists don't embrace the natural law. In short, it's too "man" centered and philosophical. It DOESN'T view the Bible as central. I quoted all of Chapter 1 and about half of Chapter 2. I end at a point in Chapter 2 where Wilson refers to the natural law as that which is written on man's heart by God, the point of connection between the Bible and Aristotle to which Mr. Van Dyke alluded. Wilson rarely cites scripture in an authoritative "verse and chapter" sense. There are however, some biblical references very mildly peppered throughout; the bulk of said contents are derived from natural law reasoning-philosophical rationalism. The same thing can be said of John Witherspoon's Lectures on Moral Philosophy which are not at all Calvinistic but rather the product of Witherspoon's naturalism and rationalism. Indeed there Witherspoon relies on Samuel Clarke the British naturalist-rationalist Anglican divine who was nearly defrocked for peddling Arianism in the Church.
Anyway, here is a long excerpt from Works which hopefully helps to put Wilson's theology of law into better context: [For the sake of space please see Wilson's quoted excerpt here at Positive Liberty.]