If one uses Shadow Evocation on a willing ally can they choose not to disbelieve?

Question

If one uses Shadow Evocation on a willing ally (e.g. Telekinetic Charge) can they choose not to disbelieve?

Shadow Evocation

Nondamaging effects have normal effects except against those who disbelieve them. Against disbelievers, they have no effect.

Disbelief

Creatures encountering an illusion usually do not receive saving throws to recognize it as illusory until they study it carefully or interact with it in some fashion.

A successful saving throw against an illusion reveals it to be false, but a figment or phantasm remains as a translucent outline.

A failed saving throw indicates that a character fails to notice something is amiss. A character faced with proof that an illusion isn't real needs no saving throw. If any viewer successfully disbelieves an illusion and communicates this fact to others, each such viewer gains a saving throw with a +4 bonus.

(my emphasis)

Voluntarily Giving up a Saving Throw

A creature can voluntarily forego a saving throw and willingly accept a spell's result. Even a character with a special resistance to magic can suppress this quality.

If I understand the above correctly,

• If the ally believes the caster actually cast Telekinetic Charge, it seems they get a save which they could forgoe and so be guaranteed the benefit of the spell. >> We're good here.
• If the ally knows the caster didn't cast Telekinetic Charge, (say because of a high Spellcraft check or because she knows the caster's spell list) they have proof that the illusion isn't real and so need no saving throw. >> Even though she "needs no saving throw", can she still choose to forego the save and be effected by the spell?

In other words, I think the question boils down to: Does one always have a choice not disbelieve an illusion, even when one has proof that it's not real?

Answer 1

To the best of my knowledge, the issue is never directly addressed. The rules, on a quick scan, appear the same as in 3.5, where this issue has been debated some as well.

The long and short of the argument is this: the statement in shadow evocation et al. is that someone who knows that it is fake does not need to save. Nothing says he does not save or may not save, just that he doesn’t have to. This is taken to mean that this is optional, and effectively someone in this position has the option of automatically succeeding on his save the same way you typically have the option of failing any save. You may, according to this logic, choose not to automatically succeed, and then, since you are now attempting a saving throw, choose to automatically fail.

Strict-RAW, this seems most accurate, though it definitely takes a few steps to get there and it’s clearly not written out explicitly. Still, the language, whether it was intended to be or not, is precise: it waives a requirement to save, it does not add a requirement to not-save.

Whether or not you should rule this way in your game is more dubious. Shadow evocation et al. are rather useful, particularly for this feature. In 3.5, greater shadow evocation was typically used to cover the loss of contingency due to the banning of Evocation as a specialist wizard. In Pathfinder, this is less of an issue (since banning is no longer so absolute anyway). Most of the time, shadow evocation et al. are most useful when the drawbacks of using them (the Will save, the quasi-reality) don’t actually affect the functioning of the spell, which is precisely in this case: buffing. Ultimately, it becomes yet another powerful and flexible tool in the wizard’s toolbox, and he’s already got a ton of those. Shadow evocation et al. are’t the most powerful of them, but maybe it’s worthwhile to you to start paring down options where you can.