Jon then began to wonder what would be wrong with wishing for something that would make the world a better place. Certainly nothing devastating could happen from that. Right?
Thinking that it would be a good idea, Jon proceeded to make a world-changing wish, which his grandfather didn't want him to make. Jon had no idea that, even with the best of intentions, a world-changing wish could be just as devastating as a wish with the worst of intentions.
Holding the stone, Jon went ahead and made his world-changing wish: "I wish ..."