Did Saruman Believe He Could Master The One Ring?

[Boromir88]

Can someone please explain to me why speculating about what Gandalf said is somehow less compelling or convincing than speculating about what Sauron thought?

By saying it's Gandalf's speculation, I'm actually implying both. Bottom line is we don't know what Sauron thought, we only know what Gandalf thought he thought. So, it would be incorrect for anyone to assert what Sauron truly thought (through Gandalf's thought), because we don't know what he actually thought except for what he tells Pippin through the Palantir. Which, what he tells Pippin through the Palantir seems to be:

1. He and Pippin will meet again.
2. He believes Saruman has something that isn't his to have.

Edit: Cross-posted with Raynor:

True, but according to Gandalf Sauron didn't just want Pippin for information, he actually believed he (or Saruman) had something else of importance that wasn't Saruman's to have. And I think we can say Gandalf's speculation in this case is accurate because we know what Sauron said to Pippin through the Palantir and he believed Saruman had something that wasn't his, and that Sauron will send for it.