Acknowledgements

As well as the references already shared throughout the text, I couldn't have arrived at these ideas without help from colleagues past and present. Thanks to everyone who has contributed valuable discussion, disagreement and feedback over the years, and especially Paul Mitchell-Gears, Charlie Tomsett, Jordan Brown, Mat Kastner, Christine Rogers and James Addison. For valuable feedback on early drafts, thanks to everyone at DabApps, Charlie Tomsett, Paul Mitchell-Gears, Carlton Gibson and Tom Parslow.