dduane:

I don’t see any real problem with the concept of someone understanding spell structure without being able themselves to do spells. After all, lots of people study the theory and operation of structural systems that they can’t actually work with in reality: possibly out of curiosity, maybe for the challenge, or various other reasons. An example would be someone who through careful study of physics and electrical theory is able to design circuitry entirely in the theoretical mode, without ever needing to plug it into the power. They know the laws they’re working with and know what will happen. 

This metaphor works fairly well because the formal structure of a wizardry and the use of the Speech are not the only things that make a spell go. The truly crucial element in any spell’s execution is the enacture quality, which vests directly in a wizard from the Powers that Be; without it no spell will fire. It’s the enacture quality that allows the wizard to do the equivalent of plugging a designed and built circuit into a power source.

This division of structure, enacture and language means there’s no reason that someone who was nonwizardly (and ideally also had a working knowledge of at least one of the nonenactive recensions of the Speech) might understand the rules for spell design well enough to build a spell circle. (But they wouldn’t be able to test it “live” or debug it without a wizard to assist.)

HTH. 🙂