IT is hard to know where to start with Donald Trump’s foreign policy. For one thing, his confused, inconsistent and dangerous pronouncements on foreign affairs and America’s place in the world simply do not deserve the word “policy” – rather they are the rantings of a rich, angry white man with a poor grasp of the facts. As President Obama pointed out at the weekend, being president requires self discipline - you have to do your homework.

President Obama also took aim at one of Mr Trump’s wildest statements. In a recent interview, the Republican nominee said that allies who did not pay their NATO dues would not be guaranteed American help if they needed it.

Not only is this a flagrant breach of the founding principle of NATO that an attack on one is an attack on all, it is a direct contradiction of what Mr Trump himself has said before – were he president, he once said, America would be a reliable ally again. President Obama’s verdict was that the Republican’s comment was yet more proof of Mr Trump’s lack of preparedness on American foreign policy.

The evidence of this lack of preparedness is in everything Mr Trump says. In his hateful and dark speech at the Republican convention, he repeated his attacks on immigrants, but his proposed ban on all Muslims entering the US (since watered down to Muslims from countries with a history of terrorism) is an offensive and unconstitutional mess. It would also do very little to prevent attacks – after all, half of the attacks in America since 2001 have been committed by people born in the United States

There is some evidence of Mr Trump rolling back on his wildest statements, but a potential president who says he will put America first at all costs represents a real threat to global stability. We know from George W Bush how disastrous a president with a poor understanding of foreign affairs can be. America, and the world, cannot afford the same to happen again.