Barack Obama, son of a black African father and a white American mother, on Tuesday becomes the 44th president of the United States. His assumption of the office is an inspiring moment for the US and the world. In part this is because he is a remarkable man with the makings of a great president. More than that, it is because the new leader of the most powerful country on earth bears witness to a momentous and distinctively American principle: that all men are created equal.

For years, black Americans saw Thomas Jefferson’s pledge in the Declaration of Independence mocked by legal impediment and lingering prejudice. As the new president has often pointed out, his election does not build the colour-blind society dreamed of by Martin Luther King; still less does it perfect the union that the founders of the United States envisaged. Nonetheless it is a huge and historic advance. It stands as a challenge to other nations to live by the principles they espouse. The world, as much as the US, is not just impressed by this inauguration, it is moved – and it is right to be.