It's 225 years old today, but the U.S. Constitution continues to be as vital and inspirational as it was when delegates at the Constitutional Convention in Philadelphia first adopted it.

Flowing from the ideals stated 11 years earlier in the Declaration of Independence and secured through the American Revolution, the Constitution as it was adopted was not simply the framework for the new government. With ratification of its first 10 amendments four years later, it became a universal declaration of human rights.

Yes, it allowed humans to be held in slavery and it was imperfect in other ways. But its arc throughout American history has been one of ever-expanding human liberty. All but one of its amendments, whether resulting from debate or civil war, have been to add to the codified and enforceable definition of freedom. The exception was the 18th Amendment, establishing Prohibition and ratified in 1919, which was repealed by the 21st Amendment, ratified in 1933.

The Constitution remains at play every day in American life. Islamic radicals want U.S. producers of a bad movie prosecuted for mocking Muhammad, but the Constitution guarantees freedom of religion and speech, for example.

There are cases that undoubtedly would make the Founders wonder about modern adherence to the Constitution. There hasn't been a declaration of war by Congress since 1941, for example, even though the Constitution gives war-making authority to Congress and the nation often has been at war over the intervening 72 years.

America's genius is that it has been a work in progress since its inception. That is possible because of a Constitution that makes liberty a fundamental guarantee amid that incessant experimentation. It isn't perfect and it often is sorely tested, but the U.S. Constitution is the best that humankind every has done.