Thanks to Matthias Felleisen, Robby Findler, Sam Tobin-Hochstadt, Jay McCarthy, Ryan Culpepper, Brian Mastenbrook, Michael Adams, Michael Ballantyne, Tim Disney, Simon Peyton Jones, Shriram Krishnamurthi, and Eelco Visser for discussions about set-of-scopes binding. Joshua Grams provided helpful editing suggestions. Anthony Carrico and Chris Brooks helpfully pointed out some typos. Thanks also to anonymous POPL reviewers for helping to improve the presentation. This work was supported by grants from the NSF.