Legal philosophers of our day, indeed virtually everyone in the legal academy, operate on the assumption that faith is out of place in any discussion of what the law is or should be. Typically, therefore, the substitute that is offered is reason. Faith is seen as antithetical to reason, and reason is considered to be the only acceptable basis for argument about law (and various other matters.)
Obviously, the Bible never countenances such a position. “The fear of the Lord is the beginning of wisdom,” says Proverbs 9:10, “[a]nd the knowledge of the holy is understanding.” (Examples of other similar statements abound: Proverbs 1:7 and 15:33, Job 28:28, Psalm 111:10, and Jeremiah 8:9.) Further, the saying credo ut intelligam, which is Latin for “I believe in order that I may understand,” has long been a motto of faithful Christians in various field, including law. (I have seen and heard this phrase attributed to both Augustine of Hippo and Anselm of Canterbury.)
In discussing his take on Thomas Aquinas’ approach to the issue of faith and reason, J. Budziszewski writes, in Written on the Heart: The Case for Natural Law, that the problem often results
from the modern prejudice that faith and reason are somehow opposites, so that the more faithful you are, the less rational you are. Thomas [Aquinas] would say that this modern prejudice is itself irrational. Both faith and reason come from God, and God does not contradict himself.
Besides, we know that human reason is finite. . . . The motto “Reason Alone!” is nonsense anyway. Reason itself presupposes faith. Why? Because a defense of reason by reason is circular, therefore worthless. Our only garuntee that human reason works is the God who made it. (p. 54)
Whether or not this accurately represents Aquinas’ position, I would not be qualified to opine. However, I would certainly agree that reason has its limits. Alone it is an unworkable and dangerous standard. It seems any proper understanding of the law must begin with the fear of the Lord. Reason has its place, but it must not and cannot be our ultimate authority.