Before Trump reneged on the nuclear deal with Iran, he repeatedly denounced it using false and misleading claims. There was no way for Trump to criticize the deal on the merits, because the deal’s supposed “flaws” weren’t really flaws at all. He couldn’t fault Iran for breaking the deal, because the IAEA had verified Iranian compliance ten times in a row. Besides, he didn’t know and didn’t care about the details of how it worked. All that mattered to him was that he considered it the worst deal ever made, and he saw it that way in large part because Obama was responsible for it. It didn’t matter to him that reneging on the deal would have negative consequences for the U.S. and the region, because he doesn’t think about the consequences of his policies. Everyone who knew anything about nonproliferation and arms control said that reneging on the deal was a serious mistake that the U.S. would come to regret, but Trump did it anyway. He did not permit reality to interfere with his self-serving story about leaving a bad deal.

The same hostility to expertise and self-serving delusion have been at work in the last few weeks since the summit in Singapore. Just a few weeks after Trump reneged on the nuclear deal, he had a meeting with Kim Jong-un that produced a weak boilerplate statement that included a vaguely-worded declaration of intentions. Trump proclaimed his triumph and asserted that the problem had been solved. Once again, it didn’t matter that practically everyone who knew anything about arms control dismissed the statement as meaningless. It didn’t matter that the summit produced no actual agreement or even the outlines of one. Trump was determined to say that he had “solved” the problem, and so he said that he did despite the mountains of evidence to the contrary. He is not permitting reality to interfere with his self-promotion.

The problem here should be obvious, but I’ll spell it out anyway. Trump has terrible foreign policy judgment, and his decision to renege on the nuclear deal proves that. Based on his record of poor foreign policy decisions (e.g., increasing support for the war on Yemen, backing the blockade of Qatar, escalating the wars he inherited, imposing the travel ban, arbitrarily hiking tariffs on allies, etc.), he doesn’t deserve the benefit of the doubt. The president doesn’t understand any of the relevant issues and doesn’t make policy decisions for substantive reasons. He makes decisions based on how it plays with a few constituencies back home, whether it repudiates his predecessor, and above all on how it makes him look on television. Trump typically justifies his actions with dishonest claims, and then celebrates his decisions by telling lies about what has been achieved. A president that routinely lies to the public about major national security issues cannot be trusted to negotiate anything on behalf of the U.S., and a president whose primary concern is to promote himself cannot be trusted to act in the best interests of the country.