GURPS Thaumatology: Sorcery

[PK]

Originally Posted by Rindis

I'm not sure offhand why a spell can't be turned off normally, but there's probably a reason.

Because those abilities are (for the most part) built with some combination of Persistent + Extended Duration, or with Affliction, neither of which offer the user a way to turn them off before their duration expires.

So that left two options: (A) add Cancellation (+10%) to every Affliction and also come up with a similar enhancement for Persistent abilities (and the handful of spells that use a third fixed-duration build), or (B) come up with a very inexpensive spell that amounts to a 2-point surcharge for flexibility.

Since (B) was both simpler and (in nearly all situations) cheaper, I went with it.