When I posted this encyclopedia of magical rules, I read over it but didn’t spend much time thinking about any of the rules in particular (I was more interested in breath than depth). Lately I’ve come to notice heavy use of the Law of Contagion in thinking in our society.

The Law of Contagion says that the history of things matters. The classic example is would you wear a sweater that belonged to a serial killer? Detection of contagion is called psychometry. It is a form of fetishism.

Our late-modern society is obsessed with authenticity. Contagious reasoning is frequently used to assess the authenticity of an item. Examples:

• a sweater knit by a native person is much more authentic than one made in a factory
• food grown on a local farm is surely more enivronmentally-friendly and nutritious
• luxury brand items are worth more than high-quality knock-offs
• real items are better than replicas

The fix for the Law of Contagion is Leibniz’s Law, the identity of indiscernibles. A serial killer’s sweater does not appear different from another sweater. The only way to determine that it is in fact the killer’s sweater is to monitor it from every moment the killer takes it off. Any time we stop monitoring it, it could be switched for an identical copy. There is always a possibility of doubt.

Believing the Law of Contagion is a weakness. You pay a higher price for things with a shiny history than identical alternatives. You ignore more important characteristics like quality and environmental footprint. Objects become hyperreal, where their contagion is more important than their function.

Some high-level neopagan did an analysis of the world’s magical traditions and came up with 26 common patterns. In a brilliant move of commercialization, he adapted them into a guide for designing magical systems for roleplaying games: a summary is available online. They’re probably invaluable to everyone from video game developers to Buffy scholars.

I’m going to use them to design an elemental magic system using urban elements (I have no idea what I’m going to do with this, which is probably why I haven’t done it yet). Although see also this mapping of all types of spells onto five elements.