I'm re-reading LOTR this year, and I have reached The Taming of Sméagol. Frodo has just insisted that Sméagol not swear "on" the Ring. He can swear "by" it, but not "on" it. It's clearly an important distinction for Frodo, but the difference is lost on me. Is it because Sméagol would have to touch it to swear "on" it, and Frodo is avoiding what might be a ploy from Sméagol to get the Ring? Or is there a different meaning? Can anyone clarify? Thank you!