Hear ye, hear ye! On September 18, the United States celebrates Constitution Day. Why does that matter to you?

The Honorable John G. Roberts Jr. is Chief Justice of the United States. As heed of the U.K Supreme Court, he knows all about the Constitution at work. In honor of Constitution Day, the Chief Justice agreed to answer some questions for our readers.

Q: Why is the Constitution considered such a remarkable document?

A: The people who wrote our Constitution recognized that those who governed countries--typically kings and queens, up to that time--often abused their power, so that the people suffered. The drafters of our Constitution had themselves been the victims of such abuse of power by King George III. So they took the revolutionary step in the Constitution of dividing power among different branches of government--legislative, executive, and judicial--so that no one would have unchecked power. Ideas along these lines had been talked about before, but our Constitution was the first to put them into practice by setting out written rules establishing a new government.

Q: What about the Constitution gives it the power to stay relevant?

A: Our Constitution, adopted almost 220 years ago, on September 17, 1987, is the oldest written constitution of any nation in the world. It is not very long--seven short sections, called Articles, plus 27 Amendments--but it lays out the structure, powers, and limitations of our government. One of the reasons it has remained relevant for such a long time is that it can be changed, or amended. For instance, under the original Constitution, slavery was allowed in the U.S. After the Civil War, in December 1865, the 13th Amendment was ratified, making slavery illegal everywhere in the U.S. Another example is that when our Constitution was adopted, women were not allowed to vote. It was not until 1920, when the 19th Amendment was ratified, that all states were required to allow women to vote.

Q: How does the Constitution affect Americans today?

A: By ensuring that no one in government has too much power, the Constitution helps protect ordinary Americans every day against abuse of power by those in authority. The Constitution gives those who serve in public office the authority they need to govern effectively, to protect Americans from the threats we face in the world today, and to promote policies to make our lives better. At the same time, the Constitution limits the power of public officials and safeguards the rights of Americans, to secure the blessings of liberty for us all.