It was sometimes provoked by assignments, then I'd go back on my own dime if I really clicked with a place. And sometimes it was just hanging out with my family or friends.

I was taking all prints and I brought them to the Magnum meetings, trying the old Josef Koudelka trick: Give them to photographers, who are getting bored during the talks about the economics of the agency, to look through with a pen. They'll separate them in two piles. I started to find the core pictures that people seem to relate to.

I realized how little I knew about my own country. I had grown up in the suburbs and, after college, I moved out of the country, so I didn't really know the place well. When I started following soldiers and their families back home, it provoked a lot of the questions about who we are as a nation, questions I realized couldn't be explored through the more limited framework of looking at the military at war and at home.

[The Middle East conflict ] just kind of ran its course for me. For a long time I could justify doing it to myself, no matter how irrational it was. It was important to me and my work. And I just don't feel it in the same way any more. When it comes up and it's important to me, I'll do it, but more out of sense of duty than desire - which used to be a big part of it.

Buzzing at the Sill is from a Theodore Roethke poem called "In a Dark Time." I'd heard a small part of it in a play, a sort of sci-fi play about morality in a virtual reality universe. Nothing to do with the book precisely, but it was a great play.

You find [reverberations from 9/11 ] in them most unexpected places, like graffiti on a wall. Sometimes it's a faded picture; sometimes it's a newspaper tacked to a wall. Sometimes it's weird paraphernalia related to it, home constructed paraphernalia. It resonates through society and continues to resonate today.

The travel ban that was imposed by the [Donald Trump] administration is a very direct reverberation of 9/11.