Wednesday morning on his television show, Joe Scarborough claimed he had spoken to a foreign policy expert who had been advising Donald Trump. During the course of that conversation, Scarborough said the expert told him Trump had asked three times why the president couldn’t use nuclear weapons. In response to the uproar that followed Scarborough’s comments, John Noonan, a former nuclear missile officer (and former adviser to Mitt Romney and Jeb Bush), published an extraordinary, and frightening, string of tweets on what it would mean for the future of American nuclear policy (and the world) if there were a “narcissist walking around with nuclear authenticators.”

Noonan wrote about his Air Force experience Wednesday morning, noting that at the time, he knew that he would only be ordered to launch in the most dire of circumstances. His concern about Trump is driven, in part, by the knowledge that a President Trump could order someone to launch for God-knows-what-reason. We spoke by phone on Wednesday afternoon. During the course of our conversation, which has been edited and condensed for clarity, we discussed the psychological tests he had to undergo, Trump’s own mental state, and why the subject of nuclear weapons can never be taken lightly.

Isaac Chotiner: Can you describe what your training was like?

John Noonan: It’s like any other job in the military where you have to learn a technical weapons system. The added element is the psychological requirements that are rightfully mandated for anyone who works either with or just around nuclear weapons. They give you a battery of tests, they screen you, you go through the normal top-secret clearance process. They want to make sure you are sane, you have no history of mental health issues. They want to make sure that you are willing to do your duty if you have to do it and, by the way, that you are aware of just how serious it is and just how grave a responsibility it is. Once you get past that, then you are mostly focused on learning the ins and outs of the weapons system, which is complex.

How do they check your sanity and make sure you know the gravity of your job?

They will give you a battery of questions and ask if you have had any prior psychological issues. They will check medical records, if they are available. As part of the top-secret clearance process, they go back and ask people who you have been associated with if you are as you present yourself. And when I did it, you do a session with your squadron commander where he goes through all the responsibilities that you will have and whether you are willing to meet those responsibilities.

One job we do not have a psychological test for is president of the United States. Have you heard people in Republican foreign policy circles speculate on Trump’s mental health?

I think anyone who listens to what Donald Trump has to say on foreign policy should be concerned. This is not the first time that he has talked about nuclear weapons in a reckless manner. Remember, he was interested in maybe having Japan or South Korea leave the U.S. nuclear umbrella and develop nuclear weapons of their own. That is contrary to decades’ worth of nuclear weapons policy and is, frankly, a terrible and dangerous idea.

Whether or not it is dumb, it does suggest that nuclear weapons is a subject he just spouts off on. He doesn’t take them seriously.

Right. I don’t know if he understands the gravity of nuclear weapons enough to take it seriously. He didn’t know what the nuclear triad was, which is something I think most high-schoolers are at least somewhat aware of. It’s a red flag. It’s a big red flag. So, do you take him at his word, if this is what he said—and it was an anonymous source to Joe Scarborough, so there is a grain of salt necessary here. But if the quote is accurate, nuclear weapons are so scary and so grave that you have to be suspicious of the fact that he is asking questions.

One of your tweets was about how you relied on the fact that the person who would order you to launch a nuke would be sane, and Trump is not. Obviously the role of the military is to follow their civilian superiors, but how should someone in the military deal with a president who might not be sane, or is, in your word, a narcissist?

It’s a great question. I will say first off that the people who do the job and the chain of command and the authentication procedures are all first-rate. We have never had one go off by accident. We have never lost one to theft. That’s really impressive. But the heart of what I am raising is: This guy is, by all accounts, a lunatic. What impact does that have on strategic command? What impact does it have on deterrence? What impact does it have on national security? I don’t know the answer to any of those questions, and I’d be lying if I said I did, but I can tell you that the sum of those answers is probably bad.

And what do you think people in the military should do about it? Resign?

I don’t know. It is dangerous to get into too deep a level of hypotheticals. What you want from a president is someone who will have clear and well-defined nuclear policy with established red lines where an enemy has no ambiguity about what the United States will do with that arsenal if lines are crossed. What is concerning about Trump is that there is just no telling which way the goal posts will be positioned. Will they shift? All the rules are out the window.

How widespread are these fears in the military?

The Military Times did a poll recently, and this is before he attacked Gold Star families and before he started talking about pulling out of NATO. And they found that Donald Trump beat Hillary Clinton 2–1. Trump was at 49 percent. But in prior polls, Romney was at 58 percent and McCain was at 56 percent. He’s counting on military support, but he is underperforming.

Do you think your analysis of Trump has been colored by the specifics of your military experience?

Well look, I have put three friends in the ground at Arlington Cemetery. The idea that my other friends—and they are numerous: I was raised in a military family, served five years in the U.S. Air Force—to think that my friends, who I consider to be as close as family in many cases, are going to have to answer to somebody who is by all accounts mentally unstable as commander in chief is very disconcerting. It’s disconcerting for the country and disconcerting for me personally. I have seen the impact of war up close, and I have felt it. Those guys and gals are the greatest among us and they deserve the best leadership this country has to offer. They won’t get it with Donald Trump.

Read more from Slate on the 2016 campaign.