Verbs and other predicates that are factive presuppose that the proposition they introduce is true. It could of course be the case that the speaker/writer is mistaken and the proposition is false -- but if the rules of English pragmatics are being followed, the speaker/writer uses a factive only when he or she is honestly convinced that the proposition is true.
There's a quick test for factive verbs/predicates that's often useful: If the verb/predicate is factive, making it negative won't change the truth value of the proposition embedded after it. Like this....
1. John knows that globalization is inevitable.
2. John doesn't know that globalization is inevitable.
3. I regret that all the tickets have been sold.
4. I don't regret that all the tickets have been sold.
5. We learned that the convention dates had been changed.
6. We didn't learn that the convention dates had been changed.
Both the positive and the negative sentences presuppose that the embedded proposition is true.
7. John thinks that globalization is inevitable.
8. John doesn't think that globalization is inevitable.
9. John believes that globalization is inevitable.
10. John doesn't believe that globalization is inevitable.
Neither the positive nor the negative sentences presuppose that the embedded proposition is true.
As is always true in linguistics, there are linguists who disagree with some or all of what I've said here. I regret that, but it's true.
[If you want to read about factives and factivity, a Google search with just "factive verbs" as your search string will take you to an abundance of material, including a lot of papers and blogposts analyzing political language in that context. I haven't been able to find the Kiparsky paper online anywhere that doesn't require a subscription; if you do find a link for it, I'd be grateful to know about it.]