Putting all of this together into an explanation where it makes sense was much harder for me than just trying to understand promises in and of themselves, which was already pretty hard. This essay was intended to be brief, and to be read slowly. If you're coming in to this not understanding promises, I would love to hear whether you found this edifying and if not what you would like to have cleared up. Also let me know how long it took you to get to the end.
One of these days I will move those extra "files" here into the main
qntm.org content management system. Before I can do that I need a better colour scheme and formatting, though.