Oh, and for rebuttal to this point, I give you James Madison. You may have heard of him.
What can he mean by saying that the Common law is not secured by the new constitution, though it has been adopted by the State Constitutions. The common law is nothing more than the unwritten law, and is left by all the constitutions equally liable to legislative alterations.
The fact is that courts were required to devise rules for problems that were not covered by statutes. They had to devise rules to decide real cases in front of them. And, that's what they did. The notion that they were divining ancient traditions, etc. was just their little way of providing themselves with legitimacy.
At the present time, you will not find any judges pretending to be applying ancient unwritten traditions to decide cases. Increasingly, there are more statutes to cover more problems and there is of course more case law (common law precedents) to handle questions not covered by statutes. But, if they cannot find any statute or precedent to resolve a question now, they are more open about the fact that they are in fact creating the rule that they apply.
I know that you are also interested in what is called natural law. Check out this article on common law, natural law, and how courts function. There is even a mention or two of the law of equity, which has more religious roots.