But someone else would have three wishes

... so Jon wondered if he could get his third wish back ... if he weren't Jon anymore. But if he became someone else, he'd never be Jon again ... assuming that this stone made permanent changes like the other one. There was only one way to find out what it did: wish. If the changes weren't permanent, he could use up his last wish by transforming into a different person who'd have three wishes. And if the changes were permanent, then at least he would know better than to make a wish that would mess things up forever. So what did he have to lose?