“Classical watches display time, but can hardly do anything else. This limitation is artificial: for instance several people confessed to be often in need of mustard… and what is the point of knowing time if you cannot get mustard?”
Includes useful theorems such as that:
1. It is possible to get as much mustard as wanted from a mustard watch.
2. A mustard watch which is its own metawatch is degenerated (using a Gödelian construction and a temporal logic).
By Y.-J. Ringard (Jean-Yves Girard). Over here.