Donald Trump is the zig-zag man. He takes positions seemingly at random, often retreats from them under fire, and then comes back to his original positions. Trying to attack him in a debate is, as Jonathan has noted, a largely futile undertaking because you never know which Trump you are about to get.

Exhibit A is his stance on war crimes. A week ago, at the Detroit debate, he was asked whether the military would follow illegal orders to kill the innocent relatives of terrorists or to undertake torture “worse than waterboarding.” His insouciant reply: “I’ve always been a leader. I’ve never had any problem leading people. If I say do it, they’re going to do it. That’s what leadership is all about.”

The next day his campaign issued a retraction in his name, in which he supposedly said that he understood “that the United States is bound by laws and treaties and I will not order our military or other officials to violate those laws and will seek their advice on such matters. I will not order a military officer to disobey the law. It is clear that as president I will be bound by laws just like all Americans, and I will meet those responsibilities.”

Last night, in the Miami debate, the issue came up again, and Trump made clear that he will not allow the laws against torture and the targeting of innocent people to deter him from doing just that. He will simply change the laws. He said:

“As far as the families are concerned, and as far as the law is concerned, we have a law — this all started with your question on waterboarding. We have a law that doesn’t allow right now water boarding. They have no laws. They have no rules. They have no regulations. They chop off heads. They drown 40, 50, 60 people at a time in big steel cages, pull them up an hour later, everyone dead. And we’re working on a different set of parameters.

Now, we have to obey the laws. Have to obey the laws. But we have to expand those laws, because we have to be able to fight on at least somewhat of an equal footing or we will never ever knock out ISIS and all of the others that are so bad.

We better expand our laws or we’re being a bunch of suckers, and they are laughing at us. They are laughing at us, believe me.”

So his position seems to be that ISIS will think we’re suckers unless we commit atrocities just as they do — and, in his worldview, that seems to be a good enough reason to violate (a.k.a. “expand”) core principles of American and international law.

This zig-zag was actually predictable: Trump couldn’t give up his pledge to commit war crimes because otherwise he would have nothing to say on the subject of ISIS. Less predictable was his zig-zag on the issue of sending troops to the Middle East.

For the past year, he has refused to commit to any ground troops to fight ISIS. Instead, he has called for indiscriminate bombing and torture. He has also pledged to “take the oil,” a stance that actually would require a long-term military occupation—but he has never acknowledged this reality presumably because he wanted to cater to isolationist sentiment.

Yet last night, when Hugh Hewitt asked him about a comment that General Lloyd Austin, head of Central Command, had made to the effect that “we need a lot more troops on the ground” to defeat ISIS, Trump did not disagree. “We really have no choice,” he said. “We have to knock out ISIS. We have to knock the hell out of them. We have to get rid of it. And then come back and rebuild our country, which is falling apart. We have no choice. I would listen to the generals, but I’m hearing numbers of 20,000 to 30,000. We have to knock them out fast.”

This should come as a shock to Trump supporters who thrilled to his denunciation of the Iraq War and who think that he is finally going to put the “neocon warmongers” in their place (Full disclosure: I am an unpaid advisor to Senator Marco Rubio’s presidential campaign). Here he is calling for more U.S. ground troops to fight ISIS than any of the other presidential candidates. But his comments barely caused a ripple for the obvious reason that no one takes anything he says seriously. Everyone, including his most fervent supporters, realizes that he is likely to say something entirely different tomorrow.

Naturally, in spite of promising to field a foreign policy team since last September, Trump still has not done so, so he has no advisers to spell out a serious plan to tackle ISIS. Nor is one necessary for his campaign, which relies entirely on a cult of personality. Actual policies are not only irrelevant but a distraction from Trump’s bombast. Facts might interfere with his grandiose, ill-informed pronouncements. (The Wall Street Journal noted that Trump claimed we sell “practically nothing” to Japan; in reality, we export $116 billion a year in goods and services to Japan—i.e., far from nothing.)

Whenever Trump was challenged on the specifics of issues of which he knows nothing — issues like Iran or Cuba or the federal budget — he retreated into his stock answer: that he will make “a great deal for the United States.” He even cited as his inspiration Ronald Reagan, noting Reagan’s relationship with Tip O’Neill to back his contention that “we need people that can make deals and can work, because right now in Washington there’s total, absolute gridlock.”

It’s true that Reagan was a master at striking deals and compromising to achieve his objectives. He said: “If you got seventy-five or eighty percent of what you were asking for, I say, you take it and fight for the rest later, and that’s what I told these radical conservatives who never got used to it.”

But here’s the difference. Reagan had clear principles that he espoused for decades — less government, a stronger defense; revive the economy, win the Cold War. He was able to use compromise to achieve his objectives because he knew what his objectives were — and so did his interlocutors, whether Tip O’Neill or Mikhail Gorbachev. With Trump, by contrast, it’s not clear that he has any principles at all beyond a belief in his general awesomeness and his supposed talent for deal-making. (A talent that, ahem, did not do him much good when four of his companies declared bankruptcy and when he launched numerous failed ventures: Trump Steaks, Trump University, Trump Airlines, Trump Vodka.) When Stephen Dinan of the Washington Times asked him, “What are some of the other issues on which you’re willing to show flexibility?”, Trump’s reply was telling: “It depends on what comes up.”

Anyone going into a negotiation with that mindset is going to be taken to the cleaners, whether by Vladimir Putin or Chuck Schumer. Being a zig-zag man may enable Trump win the Republican nomination, but it is one reason — one of many — why he would be a disaster as president.