Judge-made common law operated as the primary source of law for several hundred years, before Parliament acquired legislative powers to create statutory law. It is important to understand that common law is the older and more traditional source of law, and legislative power is simply a layer applied on top of the older common law foundation. Since the 12th century, courts have had parallel and co-equal authority to make law—"legislating from the bench" is a traditional and essential function of courts, which was carried over into the U.S. system as an essential component of the "judicial power" specified by Article III of the U.S. Constitution. Justice Oliver Wendell Holmes Jr. summarized centuries of history in 1917, "judges do and must legislate." There are legitimate debates on how the powers of courts and legislatures should be balanced. However, the view that courts lack law-making power is historically inaccurate and constitutionally unsupportable.