It is hard to put words to the gratitude I feel for my editor, Dan Frank. His assistant, Vanessa Haughton, put much thought and talent into making these sentences better. Thank you to them both and to the whole Pantheon team.
Thank you to my agent, Elyse Cheney, and to Alex Jacobs, for his elevating input in the early stages. Ilena Silverman edited an earlier version of the Adderall chapters for The New York Times Magazine. I am deeply grateful for the depth and precision she brought to that piece.
Beatrice Hogan, fact-checker extraordinaire: thank you.
Many thanks to Nick Seaver and his students at Tufts for including me in their stimulating How to Pay Attention class; those conversations have greatly enriched this book.
I have the good fortune to be surrounded by friends whose intelligence and creativity lift me up every single day. For help in ways too innumerable to document, thank you to my beloveds Risa Needleman, Aatish Taseer, Jessica Bennett, and Liese Mayer. Thank you to Dave Wallace-Wells and Ariel Schulman, who helped me hammer out the idea that would become this book. To Stefan Block, whose astonishing edits went above and beyond the bounds of friendship and to whom I am forever grateful. To Peggy Noonan for stalwart guidance on language and life; to David Sauvage for the deep read at the eleventh hour and for a decade of friendship and attention; to Emily Galvin and Jesse Rissman for their thoughtful input; and to Michael Garfinkle, Grey Gersten, Sara Wilson, Meghan Kennedy, and Rachel Smith for profound conversations they were always willing to have.
Thank you to my dear brother, Adam Schwartz, who is on this journey with me; to my in-laws Adria and Fred; to Sidne, Candy, and Franny too, for the unconditional support; and, of course, to James and Kat, always.
To my own parents, all of them, Ernie, Ellie, Zohra, and Jonathan, and especially to my mother, Marie Brenner, my north star, who took me to see the world.
And last, but mostly, to Josh, who came into my life just as I was beginning to write this book, and changed it completely. Nothing, but nothing, would be the same without you.