Nuclear weapons are often described with language that obscures the ugly reality of what is under discussion, Fihn told me when we met ahead of Trump’s Asia trip. When the president references the “full range” of U.S. military capabilities, he’s presumably including nuclear weapons. But he doesn’t say that the United States, if faced with unspecified threats of unspecified gravity, is ready to use a weapon of mass destruction to indiscriminately kill civilians, irradiate survivors, and do incalculable harm to the environment and future generations, as Fihn might put it. It’s a bit like saying, “‘If someone threatens us, I’m prepared to send my entire army with machetes [to] chop everyone up in that country,’” Fihn observed. You wouldn’t say that because you would sound crazy. But that’s essentially what’s being said regarding nuclear weapons when you cut through the euphemism and abstraction.

Nuclear weapons are made all the more abstract by the secrecy surrounding them. “We don’t really know where they are or what they’re targeting or what they’re meant to be used for,” Fihn pointed out. In his remarks in South Korea, Trump announced that the U.S. had deployed aircraft carriers and a “nuclear submarine” near the Korean peninsula. What weapons they were carrying, he didn’t say.

Efforts to stop the spread and decrease stockpiles of nuclear weapons are also hampered by fundamental contradictions in how we relate to these weapons. States with nuclear weapons, for example, routinely stress the horror of such weapons even as they credit the arms with keeping their own countries safe and strong. In South Korea, for example, Trump warned that North Korea’s pursuit of nuclear weapons endangers “humanity all over the world” while simultaneously boasting about America’s “unmatched” capacity to defend itself. It’s easier, Fihn argued, to first ban and then try to get rid of nuclear weapons, “rather than trying to reduce and eliminate something that we at the same time value and say is essential for our security.”

While emerging powers such as Brazil, Indonesia, Mexico, and South Africa have signed the Treaty on the Prohibition of Nuclear Weapons, Fihn has yet to persuade any nuclear-weapons states or their treaty allies—including NATO members, Japan, and South Korea, which count on protection from their nuclear-armed partners—to support the initiative. She’s even struggling to secure the backing of countries that are more loosely allied with nuclear-weapons states but still hesitant to break with them, like her native Sweden. (“New opinion poll: 9/10 Swedes want Sweden to sign the #NuclearBan,” Fihn recently tweeted. “Who gets to decide over Swedish policy? Its people or the United States?”)

But Fihn claims she doesn’t need these holdouts, at least not right away. Her goal is to “reframe the debate” and “set a clear norm that [nuclear weapons are] unacceptable,” and then use the law to effect change. “We can’t keep murder legal just because it still happens,” she reasoned. “It’s not like we can wait until there’s no more murders ever and then make it illegal.”