Functional Magic is a trope that refers to magic that goes beyond mere plot device to serve as a tool, science, technology, art, or philosophy. Functional Magic is magic that functions consistently from scene to scene, and can be understood beyond the A Wizard Did It Hand Wave.
Game and Story Use
- Role-playing games pretty much need functional magic (if they feature magic at all). Some really rules-lite Indy RPGs might be able to get away with nothing but plot magic and improvisation, but it's hard to sustain that for more than a short-shot. Eventually, the players need to understand magic enough to defend against it, prepare for it, and make the most of it. If it remains as nebulous as green rocks or the green lantern ring, that's really hard to do. See Phlebotinum for further discussion of this topic.
- In a setting where magic is dangerous or wild, one can justify non-functional magic and/or hiding the laws of magic from the player characters. For example, in a Call of Cthulhu campaign, you could certainly get away with concealing the limits of magic from the players unless they pay precious sanity points to figure it out.