I am grateful to my friends and colleagues Sarah Fitz-Claridge, Alan Forrester, Herbert Freudenheim, David Johnson-Davies, Paul Tappenden and especially Elliot Temple and my copy-editor, Bob Davenport, for reading earlier drafts of this book and suggesting many corrections and improvements, and also to those who have read and helpfully commented on parts of it, namely Omri Ceren, Artur Ekert, Michael Golding, Alan Grafen, Ruti Regan, Simon Saunders and Lulie Tanett.
I also want to thank the illustrators Nick Lockwood, Tommy Robin and Lulie Tanett for translating explanations into images more accurately than I could have hoped for.