Griffin takes Sanderson's law and smashes it to pieces over her sorcerous knee. Though the reader is certainly given enough of the pieces to understand each scene, they are never able to actually understand the magic of London. Likely because it, like the city itself, is simply too large, too varied, and too complex for something so pat as comprehension. Some parts, of course, are easy; this is urban sorcery, a magic of brick and neon (p. 26). Still, the reader never knows the exact limit of Swift's capabilities, and there is always the possibility of some previously unpredictable, new magical solution or element coming into play to save the day or alter the course of events. This could, obviously, be a recipe for rampant deus ex machina, but that's not the way things turn out at all.
The Midnight Mayor looks at what makes a city a city, at how people shape each other, and at whether it is the inanimate city that shapes its citizens or its citizens that shape the city. It is fascinating stuff, and the pages in which it is discussed in concentrated form towards the book's end manage to be both philosophical and to never break from the character or narrative established; these big questions are woven into the fabric of the story. Eventually, there comes forth the idea of the city –and, by extension, its denizens – as itself/themselves forming a "higher power" (p. 298).