Spellwilling is the practice of bringing about an alteration in reality by will alone; its practitioners are called spellwillers. Because it has no somatic, vocal, situational, or material requirements, it is the most powerful and versatile ability. Many means by which spellworkers can be prevented from spellworking can’t be used against spellwillers.
It is not an outright denial of the fact that the person experiences, such as saying “this wall is black” when it is clearly white; if a person attempts this, nothing will change due to the self-derogation rule: he knows that he only wants the wall to be black, but his experience tells him it is white, and so he himself has faith that it is white, and so it stays white.
Generally a spellwiller must first be convinced that he can alter reality by will alone (a rare occurrence, as explained in the rarity of magic section). Generally this is couched in the context of a certain procedure that he follows. Typically a spellwiller will think to themselves of what change they want to bring about, and think to themselves that at a specified moment, reality will change accordingly because he wills it so. This gets around the issues that 1) while he’s thinking of what change he’d like, reality is obviously not changing; he must specify a moment of change for the change to occur, unless the change can be gradual; 2) he attributes the alteration of reality to some cause (“by my will”), to get around the fact that normally things don’t change without good reason. The specified moment is usually a “thought snap” - the spellwiller essentially thinks “now” to himself for a split second, and at that moment the change should manifest.