Published online by Cambridge University Press: 09 November 2011
* I wish to express my gratitude to Fátima Silva and Oliver Taplin, who read an earlier draft of this article and encouraged me with illuminating support and critical advice. Javier Campos was a source of inspiration for many of the ideas expressed here. I am particularly grateful to an anonymous referee, whose observations and comments have led to substantial improvements in the final version. Finally, my special thanks to John Wilkins for his accurate revision. Any remaining inaccuracies are my sole responsibility.