The Laws of Magic
(Based on the list in Isaac Bonewit's Real Magic, these laws were one of George's first lessons when he began studying magic in the occult library of Demetrius Katsoulakis.)
1) The Law of Cause & Effect: "Exactly the same actions done under exactly the same conditions will always be associated with exactly the same results." (But all those 'exactly's are hard to get.)
2) The Law of Knowledge: "Understanding brings control." If you know all there is to know about something, then you have absolute and total control over it. "Knowledge is power."
2a) The Law of Self-Knowledge: The most important kind of knowledge is knowledge about yourself.
(Everything else depends on those first two, but there are others that build on them, like:)
3) The Law of Names: "Knowing the complete and total true name of a phenomenon or entity gives you complete control over it. (almost all phenomena in magic are personified and can be considered 'entities' or beings)."
a) In a simple language a name is a definition of that which is named.
b) Names are associational; they jog our memories.
4) Law of Words of Power: "There are certain words that are able to change and influence the inner and outer reality of those saying them. The power is thought to lie in the very sounds of the words themselves."
5) Law of Association: "If two things, "A" and "B", have something in common (anything!), that thing can be used to control both, and "A" and "B" have a mutual influence on each other, depending upon the size of the thing shared.
5a) The Law of Similarity: "Sympathetic Magic": If you want to make a broom fly, put some bird feathers on it, etc. "Lookalikes are alike." Anything any object or person or idea that reminds you of, or is connected with a particular phenomenon or entity contains some of that entity's power and can be used as if it were the entity itself.
5b) The Law of Contagion: "Things once in contact continue to interact after separation." (This is the 'voodoo' thing, using toenails, etc. against someone. The emphasis is on things that were once in physical contact.)
6) Law of Identification: By maximum identification between your Self (your "metapattern") and that of another entity, you can actually become that entity and wield its power.
(This notion is part of the magic system used in Unknown Armies. It can also be found in Thomas Harris' novels like Red Dragon and the Michael Mann adaptation, Manhunter).
7) The Laws of Invocation & Evocation: "You can conjure up from, respectively, the inside of and outside of your metapattern, real entities." In other words, Essence works.